S550 TPMS sensors
06-26-2008, 10:43 AM
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2007 S550/1990 300CE
S550 TPMS sensors
After reading the archives I am still confused by
what the dealers service writer told me. If I add
the proper TPMS sensors to a second set of wheels
and tires, I will have to have the dealer reset or
identify the new sensors every time I change the
wheels back and forth. Is this true, or will the
COMAND reset menu do the trick?
TIA, Don
what the dealers service writer told me. If I add
the proper TPMS sensors to a second set of wheels
and tires, I will have to have the dealer reset or
identify the new sensors every time I change the
wheels back and forth. Is this true, or will the
COMAND reset menu do the trick?
TIA, Don
06-26-2008, 01:48 PM
#2
Super Member
Not true. The command will reset itself after you drive it for about 15 mins. I switch my rims every 3-4 months with different sets of tpms in each wheels
06-26-2008, 01:55 PM
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I find it odd that the new system even tries to detect the current tyre pressure and you would not need to reset the system even if tyre pressures are changed. I mean how does it then cope with a small leak on all tyres (OK, very unlikely to happen).
06-26-2008, 02:35 PM
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True for the new W221 TPMS implementation. I learned this only recently. I only have TPMS on the W211 and it is still with the older Beru system where you do have to reset the system after wheel changes and also after changing tyre pressures.
I find it odd that the new system even tries to detect the current tyre pressure and you would not need to reset the system even if tyre pressures are changed. I mean how does it then cope with a small leak on all tyres (OK, very unlikely to happen).
I find it odd that the new system even tries to detect the current tyre pressure and you would not need to reset the system even if tyre pressures are changed. I mean how does it then cope with a small leak on all tyres (OK, very unlikely to happen).
The newer system still must be calibrated when you change sensors or tires, using a COMAND or cluster action. The TPMS unit in the car "knows" the proper inflation (that stated on the fuel-filler flap). It's critical that the tires initially be filled to those pressures (that's why an accurate external pressure gauge is still a must-have), and the COMAND or cluster "reset" operation be performed. This teaches the TPMS that the sensors are currently reading the baseline values that it's preprogrammed with.
The TPMS sensors very precisely measure changes in pressure, so assuming the baseline was set accurately will track pressure changes with great accuracy. But they cannot determine absolute pressure, so if you don't calibrate them the system will not be very useful. Many, if not most, owners don't know this.
06-26-2008, 02:37 PM
#5
MBWorld Fanatic!
After reading the archives I am still confused by
what the dealers service writer told me. If I add
the proper TPMS sensors to a second set of wheels
and tires, I will have to have the dealer reset or
identify the new sensors every time I change the
wheels back and forth. Is this true, or will the
COMAND reset menu do the trick?
TIA, Don
what the dealers service writer told me. If I add
the proper TPMS sensors to a second set of wheels
and tires, I will have to have the dealer reset or
identify the new sensors every time I change the
wheels back and forth. Is this true, or will the
COMAND reset menu do the trick?
TIA, Don
06-27-2008, 01:59 AM
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TPMS sensors are a great lesson in precision (which they have) versus accuracy (which they don't).
The newer system still must be calibrated when you change sensors or tires, using a COMAND or cluster action. The TPMS unit in the car "knows" the proper inflation (that stated on the fuel-filler flap). It's critical that the tires initially be filled to those pressures (that's why an accurate external pressure gauge is still a must-have), and the COMAND or cluster "reset" operation be performed. This teaches the TPMS that the sensors are currently reading the baseline values that it's preprogrammed with.
The TPMS sensors very precisely measure changes in pressure, so assuming the baseline was set accurately will track pressure changes with great accuracy. But they cannot determine absolute pressure, so if you don't calibrate them the system will not be very useful. Many, if not most, owners don't know this.
The newer system still must be calibrated when you change sensors or tires, using a COMAND or cluster action. The TPMS unit in the car "knows" the proper inflation (that stated on the fuel-filler flap). It's critical that the tires initially be filled to those pressures (that's why an accurate external pressure gauge is still a must-have), and the COMAND or cluster "reset" operation be performed. This teaches the TPMS that the sensors are currently reading the baseline values that it's preprogrammed with.
The TPMS sensors very precisely measure changes in pressure, so assuming the baseline was set accurately will track pressure changes with great accuracy. But they cannot determine absolute pressure, so if you don't calibrate them the system will not be very useful. Many, if not most, owners don't know this.
The Beru system certainly was taught in with the reset. What ever pressure values you had in each wheel, the setting at the time of reset was taken as the correct value and a certain drop from that reference fired the alarm. The system also measures tyre temperature, so it does not really matter if the setting is reset at low or high temp.
Personally I would expect the same from the new Siemens system or any other system but then again, the technical documentation explains that the system automatically learns the current tyre pressure settings too. This could be a mistake in the documentation too, I've seen mistakes elsewhere but I cannot prove this statement being wrong (or right).
The reset feature in the cluster menu must serve a purpose. Now that the new system does learn new sensors and rotated tyres automatically (unlike the old Beru system, be it good or bad), I wonder what else could this be for except setting the correct reference. Sounds odd if it is only to avoid a warning after tyre pressures have been intentionally reduced significantly (before the system would learn the new settings).
You are right that the sensors are more accurate for relative measurements but at least the Beru system on my W211 is pretty accurate in absolute terms too (I have experience about some 3 sets of sensors).
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06-27-2008, 09:27 AM
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2007 S550/1990 300CE
S550 TPMS sensors
Thank you all for the input. Good information.
Just as I figured, the dealer's service writer
doesn't know the car. Unfortunately, this has
happened several times in the past.
Now, do any of you know where to purchase the
correct sensors at a "reasonable" price? I'm in
the northwest near Seattle-Tacoma.
Don
Just as I figured, the dealer's service writer
doesn't know the car. Unfortunately, this has
happened several times in the past.
Now, do any of you know where to purchase the
correct sensors at a "reasonable" price? I'm in
the northwest near Seattle-Tacoma.
Don
06-27-2008, 09:55 AM
#9
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I've never seen technical documentation claiming the system is coded for the tyre pressures on the fuel-filler flap. In my opinion it is an urban legend. Why would it need to know the fuel filler flap values if it anyway is reset to the current tyre pressure values? Another one is that the owner may change tyre size to something that asks a different tyre pressure. Even better, the spare parts (sensors obviously but also the control module) come with the same part number for different models and there is no coding involved when parts are changed.
The Beru system certainly was taught in with the reset. What ever pressure values you had in each wheel, the setting at the time of reset was taken as the correct value and a certain drop from that reference fired the alarm. The system also measures tyre temperature, so it does not really matter if the setting is reset at low or high temp.
Personally I would expect the same from the new Siemens system or any other system but then again, the technical documentation explains that the system automatically learns the current tyre pressure settings too. This could be a mistake in the documentation too, I've seen mistakes elsewhere but I cannot prove this statement being wrong (or right).
The reset feature in the cluster menu must serve a purpose. Now that the new system does learn new sensors and rotated tyres automatically (unlike the old Beru system, be it good or bad), I wonder what else could this be for except setting the correct reference. Sounds odd if it is only to avoid a warning after tyre pressures have been intentionally reduced significantly (before the system would learn the new settings).
You are right that the sensors are more accurate for relative measurements but at least the Beru system on my W211 is pretty accurate in absolute terms too (I have experience about some 3 sets of sensors).
The Beru system certainly was taught in with the reset. What ever pressure values you had in each wheel, the setting at the time of reset was taken as the correct value and a certain drop from that reference fired the alarm. The system also measures tyre temperature, so it does not really matter if the setting is reset at low or high temp.
Personally I would expect the same from the new Siemens system or any other system but then again, the technical documentation explains that the system automatically learns the current tyre pressure settings too. This could be a mistake in the documentation too, I've seen mistakes elsewhere but I cannot prove this statement being wrong (or right).
The reset feature in the cluster menu must serve a purpose. Now that the new system does learn new sensors and rotated tyres automatically (unlike the old Beru system, be it good or bad), I wonder what else could this be for except setting the correct reference. Sounds odd if it is only to avoid a warning after tyre pressures have been intentionally reduced significantly (before the system would learn the new settings).
You are right that the sensors are more accurate for relative measurements but at least the Beru system on my W211 is pretty accurate in absolute terms too (I have experience about some 3 sets of sensors).
06-27-2008, 10:01 AM
#10
MBWorld Fanatic!
Thank you all for the input. Good information.
Just as I figured, the dealer's service writer
doesn't know the car. Unfortunately, this has
happened several times in the past.
Now, do any of you know where to purchase the
correct sensors at a "reasonable" price? I'm in
the northwest near Seattle-Tacoma.
Don
Just as I figured, the dealer's service writer
doesn't know the car. Unfortunately, this has
happened several times in the past.
Now, do any of you know where to purchase the
correct sensors at a "reasonable" price? I'm in
the northwest near Seattle-Tacoma.
Don
06-27-2008, 11:17 AM
#11
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Can you help me reading the exact point at the manual. To me the manual only states that resetting takes the current inflation values for a reference point. I did not find it stating that it would take the values from the fuel-filler flap. That was what I claimed to be an urban legend (I don't mind that assumption being proven wrong).
Coming back to what the manual states, that is pretty much what is explained for the Beru system at different technical documents. I'm sure the part in the manual is correct (that isn't always the case equally to WIS and other technical documents). The point I was wondering previously was about the tyre pressure reference point adaptation after reset. The technical documentation claims that the car system adapts to current values automatically. I already said that sounds odd but I cannot prove it being wrong. I also consider this feature still being possible even if the manual did not tell about it (but my assumption is that the MB technical document is more or less wrong). If anyone is interested about a reference to the document, I could try to find it.
I may well have misunderstood you earlier post, sorry if that is the case but this sentence "The TPMS unit in the car "knows" the proper inflation (that stated on the fuel-filler flap)" to me reads that the car system knows the values written to the fuel filler flap. I on the other hand was claiming that the system does not use the user manual tyre pressure values as the correct reference point.
Coming back to what the manual states, that is pretty much what is explained for the Beru system at different technical documents. I'm sure the part in the manual is correct (that isn't always the case equally to WIS and other technical documents). The point I was wondering previously was about the tyre pressure reference point adaptation after reset. The technical documentation claims that the car system adapts to current values automatically. I already said that sounds odd but I cannot prove it being wrong. I also consider this feature still being possible even if the manual did not tell about it (but my assumption is that the MB technical document is more or less wrong). If anyone is interested about a reference to the document, I could try to find it.
I may well have misunderstood you earlier post, sorry if that is the case but this sentence "The TPMS unit in the car "knows" the proper inflation (that stated on the fuel-filler flap)" to me reads that the car system knows the values written to the fuel filler flap. I on the other hand was claiming that the system does not use the user manual tyre pressure values as the correct reference point.
06-27-2008, 12:13 PM
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2007 S550/1990 300CE
S550 TPMS sensors
Gentlemen,
Is it possible that resetting the system after changing the tire pressures is to adjust the acceptable pressure range in the computer to the owners preferred pressure?
For example, if one sets cold pressures to 34lbs. the system may warn you when the pressures drop below 30lbs. Whereas, someone else who prefers 28lbs. cold pressure may get a warning when pressures drop below 24lbs. This assumes resetting was performed. I really don't know the ranges. Just wondering if this may be how it works?
Don
Is it possible that resetting the system after changing the tire pressures is to adjust the acceptable pressure range in the computer to the owners preferred pressure?
For example, if one sets cold pressures to 34lbs. the system may warn you when the pressures drop below 30lbs. Whereas, someone else who prefers 28lbs. cold pressure may get a warning when pressures drop below 24lbs. This assumes resetting was performed. I really don't know the ranges. Just wondering if this may be how it works?
Don
06-27-2008, 12:27 PM
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Gentlemen,
Is it possible that resetting the system after changing the tire pressures is to adjust the acceptable pressure range in the computer to the owners preferred pressure?
For example, if one sets cold pressures to 34lbs. the system may warn you when the pressures drop below 30lbs. Whereas, someone else who prefers 28lbs. cold pressure may get a warning when pressures drop below 24lbs. This assumes resetting was performed. I really don't know the ranges. Just wondering if this may be how it works?
Don
Is it possible that resetting the system after changing the tire pressures is to adjust the acceptable pressure range in the computer to the owners preferred pressure?
For example, if one sets cold pressures to 34lbs. the system may warn you when the pressures drop below 30lbs. Whereas, someone else who prefers 28lbs. cold pressure may get a warning when pressures drop below 24lbs. This assumes resetting was performed. I really don't know the ranges. Just wondering if this may be how it works?
Don
I'm not sure actually if whoover has the same or a different opinion. The reference to the fuel filler flap figures was confusing.
Cold pressure would not be an issue because the sensors measure the tyre temperature and take into account the reduced pressure from cold tyres. My understanding is that the TPMS reading at the cluster is "compensated" for the tyre temperature too but I'm not sure about this. Would be easy to check by reading the display at a cold winter morning and then after driving and making the tyres warm up.
06-27-2008, 03:56 PM
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Yes, sure, this is what it has been previously as I stated and this is what I'm assuming from the Siemens system too. The one preferring higher tyre pressures from those at the fuel-filler flap, should get a warning at a higher tyre pressure level, if there is a leak.
I'm not sure actually if whoover has the same or a different opinion. The reference to the fuel filler flap figures was confusing.
Cold pressure would not be an issue because the sensors measure the tyre temperature and take into account the reduced pressure from cold tyres. My understanding is that the TPMS reading at the cluster is "compensated" for the tyre temperature too but I'm not sure about this. Would be easy to check by reading the display at a cold winter morning and then after driving and making the tyres warm up.
I'm not sure actually if whoover has the same or a different opinion. The reference to the fuel filler flap figures was confusing.
Cold pressure would not be an issue because the sensors measure the tyre temperature and take into account the reduced pressure from cold tyres. My understanding is that the TPMS reading at the cluster is "compensated" for the tyre temperature too but I'm not sure about this. Would be easy to check by reading the display at a cold winter morning and then after driving and making the tyres warm up.
06-28-2008, 03:59 AM
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Did you read the manual pages I posted? I'm not sure if you mean my reference is confusing or the manual is confusing. It's pretty explicit. Sorry to appear dense, but if we're not working from the same facts (those two pages I posted) we're going to be talking at cross purposes.
I did read the manual text, but of course I may have missed something that was essential (I don't think I would be the first one with that).
You neither helped pointing the exact text in the manual when I asked for it. You only posted two pages instead of referring the full manual but even there was quite a lot of "redundant" text.
Let me guess: you are talking about the importance or function of the reset feature because I was referring to a workshop document explaining the system automatically adapts to the "current pressure values"?
I never claimed reset would not do this, I was just referring to the documentations saying "this isn't completely necessary". Myself I find this odd but I did not write the document. Also, even if the system did this, it would not be any conflict with the reset feature. I don't remember but I'm assuming the same document talks about the reset feature too (have you had a look at this document, would you like to have a copy?).
The other part of this "arguing" is your reference to the "fuel-filler flap tyre pressure figures". From this reference and the sentence you wrote, I would interpret you meaning that the TPMS system knows these values and would take this into use from reset. I don't think you wrote exactly this but I don't see any other relevance with the reference to the flap figures. I'm guessing this was just a bit carelessly written and you actually did not mean the system would know the filler flap figures and would not use those for reference from reset but the actual current tyre pressure values?
I'm not able to express the above very clearly, perhaps a summary:
- do we have the same understanding that from the cluster menu TPMS reset the system would take the current tyre pressure values for a reference and would warn when tyre pressures change too much from these figures?
- can you clarify, does the TPMS system use the fuel-filler flap figures somehow?
Sorry for insisting on details, I don't feel I had posted incorrect info (I'm not claiming you did, I'm claiming you did write some parts a bit carelessly that would get interpreted as incorrect info while you probably did not mean that). I may have written something that was not easy to interpret, sorry about that. I'm willing to accept a mistake too but that is something where I want to get details clearly covered before I'm willing to accept.
Sorry about using the "urban legend" phrase too, it was not intended for you but the claim that has appeared before, I should have kept using the usual dull words.
06-28-2008, 10:42 AM
#16
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I hope you didn't take "did you read ..." as snide or sarcastic in any way. It was really to make sure we were using the same fodder for our discussion.
In the US, the law requires TPMS to signal the driver when a tire reaches a specific underinflation percentage of the "cold placard pressure." This is why the central TPMS unit must know the pressure setting and why, in the US, there must be a fuel-filler label that duplicates or updates the information that may be found on the door pillar. In fact, the legal requirement for that fuel-filler information is that it be the pressure that is programmed into the car's TPMS control unit. This all comes from the TREAD Act, mandating TPMS in the US. Search for the word "placard" in this link:
http://www.nhtsa.dot.gov/cars/rules/...l/execsum.html
A more detailed discussion of the requirement is at:
http://www.nhtsa.dot.gov/cars/rules/...PMS-08-05.html
The actual text of the law states:
This document establishes two compliance options for the short-term, for the period between November 1, 2003, and October 31, 2006. Under the first compliance option, a vehicle''s TPMS must warn the driver when the pressure in any single tire or in each tire in any combination of tires, up to a total of four tires, has fallen to 25 percent or more below the vehicle manufacturer''s recommended cold inflation pressure for the tires, or a minimum level of pressure specified in the standard, whichever pressure is higher. Under the second compliance option, a vehicle''s TPMS must warn the driver when the pressure in any single tire has fallen to 30 percent or more below the vehicle manufacturer''s recommended cold inflation pressure for the tires, or a minimum level of pressure specified in the standard, whichever pressure is higher. Compliance with the options would be phased in during that period by increasing percentages of production.
http://www.nhtsa.dot.gov/cars/rules/...TirePresFinal/
Part of our DOT testing of every model car is the accuracy of the TPMS warning onset within the specified time and specified percentage of underinflation from the placard specification. This is why the TPMS control unit must absolutely be programmed with the recommended cold inflation pressures.
The text that I considered from the manual was:
It is the driver's responsibility to calibrate the TPMS on the cold inflation pressure... Using the Tire and Loading Information placard ... make sure the tire inflation pressure is correct...
Pause for interpretation -- Because we are calibrating TPMS, I would not expect this instruction refers to the TPMS read-out at the moment; in other words, this instruction requires you to assure your tire pressures are cold and match the placard when verified by a separate gauge. Perhaps this is a point where our understandings are different. If you feel that calibration involves confirming that the tires match the placard recommendations as evidenced by the TPMS before you proceed, I would better understand your argument. But I would then ask, why would the following be "calibration." Continuing ...
Reactivate the TPMS after adjusting the tire inflation pressure ... The message "Use current pressure values as new reference values To confirm press "OK" "...
I interpreted this to mean that you were calibrating the system by telling it that these strain-gauge values should be mapped to the placard pressures, which the law requires the system to use. The only other interpretation that I can think of is that you're reprogramming the system to use whatever pressures the tire currently have as "nominal" and raise an underinflation alert based on these new values. But that is not allowed by the law, which is very clear that alerts must be based on placard values, not user settable ones.
This is the basis of my conclusion that calibration involves asserting to the system that the tires are cold and set as per the placard. I have no direct evidence. (I would be interested in the technical documentation you have, by the way.) If you have a different calibration scenario that matches this description and the requirements of the TREAD Act, I'd be happy to discuss it. I truly have no emotional investment in my theory.
BTW, I have made the assumption that the system works the same worldwide even though some operational requirements we're discussing are US Federal. As far as I know, the same system is used in all markets. That may not be correct and could complicate matters.
In the US, the law requires TPMS to signal the driver when a tire reaches a specific underinflation percentage of the "cold placard pressure." This is why the central TPMS unit must know the pressure setting and why, in the US, there must be a fuel-filler label that duplicates or updates the information that may be found on the door pillar. In fact, the legal requirement for that fuel-filler information is that it be the pressure that is programmed into the car's TPMS control unit. This all comes from the TREAD Act, mandating TPMS in the US. Search for the word "placard" in this link:
http://www.nhtsa.dot.gov/cars/rules/...l/execsum.html
A more detailed discussion of the requirement is at:
http://www.nhtsa.dot.gov/cars/rules/...PMS-08-05.html
The actual text of the law states:
This document establishes two compliance options for the short-term, for the period between November 1, 2003, and October 31, 2006. Under the first compliance option, a vehicle''s TPMS must warn the driver when the pressure in any single tire or in each tire in any combination of tires, up to a total of four tires, has fallen to 25 percent or more below the vehicle manufacturer''s recommended cold inflation pressure for the tires, or a minimum level of pressure specified in the standard, whichever pressure is higher. Under the second compliance option, a vehicle''s TPMS must warn the driver when the pressure in any single tire has fallen to 30 percent or more below the vehicle manufacturer''s recommended cold inflation pressure for the tires, or a minimum level of pressure specified in the standard, whichever pressure is higher. Compliance with the options would be phased in during that period by increasing percentages of production.
http://www.nhtsa.dot.gov/cars/rules/...TirePresFinal/
Part of our DOT testing of every model car is the accuracy of the TPMS warning onset within the specified time and specified percentage of underinflation from the placard specification. This is why the TPMS control unit must absolutely be programmed with the recommended cold inflation pressures.
The text that I considered from the manual was:
It is the driver's responsibility to calibrate the TPMS on the cold inflation pressure... Using the Tire and Loading Information placard ... make sure the tire inflation pressure is correct...
Pause for interpretation -- Because we are calibrating TPMS, I would not expect this instruction refers to the TPMS read-out at the moment; in other words, this instruction requires you to assure your tire pressures are cold and match the placard when verified by a separate gauge. Perhaps this is a point where our understandings are different. If you feel that calibration involves confirming that the tires match the placard recommendations as evidenced by the TPMS before you proceed, I would better understand your argument. But I would then ask, why would the following be "calibration." Continuing ...
Reactivate the TPMS after adjusting the tire inflation pressure ... The message "Use current pressure values as new reference values To confirm press "OK" "...
I interpreted this to mean that you were calibrating the system by telling it that these strain-gauge values should be mapped to the placard pressures, which the law requires the system to use. The only other interpretation that I can think of is that you're reprogramming the system to use whatever pressures the tire currently have as "nominal" and raise an underinflation alert based on these new values. But that is not allowed by the law, which is very clear that alerts must be based on placard values, not user settable ones.
This is the basis of my conclusion that calibration involves asserting to the system that the tires are cold and set as per the placard. I have no direct evidence. (I would be interested in the technical documentation you have, by the way.) If you have a different calibration scenario that matches this description and the requirements of the TREAD Act, I'd be happy to discuss it. I truly have no emotional investment in my theory.
BTW, I have made the assumption that the system works the same worldwide even though some operational requirements we're discussing are US Federal. As far as I know, the same system is used in all markets. That may not be correct and could complicate matters.
Last edited by whoover; 06-28-2008 at 10:51 AM.
06-28-2008, 12:12 PM
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Whoover, thanks for all that info. Those US legal issues are completely new to me. I don't think I can even handle all of that even if you explain thoroughly.
The TPMS system is the same worldwide (except the operating frequencies) but regional variations may exist through version coding and SW versions. I'm not sure if differences exist but it is possible.
The rules seem to state clearly that the TPMS system should know the "fuel-filler flap figures". Until now I was not aware of that. I have not seen that mentioned in workshop documents (documents do not tell all details).
I still have a few points where I'm not sure what your interpretation is (although I'm sure you did mention that):
- I interpret you considering that the TPMS system must be fully responsible on its own about the minimum tyre pressures allowed for the car, it is not possible to transfer the responsibility for the user. If the user calibrated the system when tyre pressures are too low, the system should not accept this as the "nominal" value. From the different US requirements I interpret myself this being the case (within the given accuracy requirements).
- I'm not sure at all if I understood how you interpret the TPMS calibration (reset from the IC menu). My understanding still is that the current tyre pressure values are taken for a reference point, the warning is given once the tyre pressures go lower than this by a certain amount (percentage), with one exception to be discussed later. Another interpretation would be that the TPMS system assumes the tyres are at the fuel-filler flap values and the TPMS reading is calibrated at reset to show those values. The latter interpretation can be shown incorrect with a simple test (I've done this with my Beru system, I cannot do it with the Siemens system as my W221 does not have RDK, just RDW). If you inflate tyres more than advised and reset TPMS, the IC reading would show the actual tyre pressure values instead of the fuel-filler flap values (again within the sensor's accuracy, which is pretty good).
Inspired by your references to the US legal requirements I had a visit at Star Diagnosis computer. I know the sensors have no version coding or parameter adaptation etc. But I had a look at the procedure of changing the TPMS control module. The point is that this same part number is used on different vehicles and in order for the system to take care of the legal requirements, it would need to know the fuel-filler flap figures. Guess what, there are parameter adaptations including the setting for target tyre pressure values for the front and the rear axle independently (no calibration of individual sensors, those are calibrated at production and do not need any follow-up).
I conclude so far that the fact that the TPMS system is aware of the tyre pressure values assigned for the car (at least the current Siemens system, I did not check the same for the Beru system).
The car manual text sounds conflicting with the above. I'm assuming it actually isn't. I'm assuming the calibration by IC reset really taking the current tyre pressure values as the nominal values from which tyre deflation by a certain value (percentage) is detected. This all with one exception, if the tyres are inflated to a lower value than that reading on the fuel-filler flap, the current reading would not be taken for a reference value (even if the manual does not mention any exception, exceptions like would make the manual unnecessarily confusing).
It would be relatively straightforward to test if the above is correct by calibrating tyres to a very high value on one hand and testing the gauge reading where a warning is given when one tyre is deflated. I'm assuming a warning is given at a way higher value than if the calibration was done for correct tyre pressures. Another test should be done at significantly too low tyre pressure values. An immediate warning should appear in this case.
I'd conclude that I was both wrong and right previously: The current tyre pressure values are taken for reference by TPMS if tyres are inflated at least to the values declared by the manufacturer. Otherwise the programmed value is used (this equals the values on the flap). Whoover and others, do you see it differently?
I still have to refresh my memory for the workshop documents. It is easy to spot some new stuff when knowing what to expect.
Edited: I had a look at the workshop documents, I'll edit the info in, the thread really does not deserve a bump.
I guess one point for different views was the comment that the Siemens TPMS automatically learns new tyre pressure values. GF4015P000102SX specifically states that "In normal application cases (wheel exchange or the driver adjusts new pressure values) filling detection automatically determines new specified (reference) values. "Filling detection" occurs if no pressure change (temperature compensated) occurs within monitoring period and tire pressures are above the minimum for the model series.
I would conclude that the workshop documents clearly cover the "self adaptation" for reference pressures. In all typical scenarios the manual activation should not be necessary (it should be done and is also well covered by the documents). There is a minor hint to the SDS calibration when the minimum allowed tire pressure for the model series is mentioned.
Previously I was "complaining" that the autonomous pressure reference adaptation doesn't make sense but since the car is using certain "plausibility" checks and taking into account that the new system is not able to warn for sudden pressure drop (only "rapid"), I guess this makes sense after all. Fully manual operation would be better for an experienced driver but not good for an average driver).
The TPMS system is the same worldwide (except the operating frequencies) but regional variations may exist through version coding and SW versions. I'm not sure if differences exist but it is possible.
The rules seem to state clearly that the TPMS system should know the "fuel-filler flap figures". Until now I was not aware of that. I have not seen that mentioned in workshop documents (documents do not tell all details).
I still have a few points where I'm not sure what your interpretation is (although I'm sure you did mention that):
- I interpret you considering that the TPMS system must be fully responsible on its own about the minimum tyre pressures allowed for the car, it is not possible to transfer the responsibility for the user. If the user calibrated the system when tyre pressures are too low, the system should not accept this as the "nominal" value. From the different US requirements I interpret myself this being the case (within the given accuracy requirements).
- I'm not sure at all if I understood how you interpret the TPMS calibration (reset from the IC menu). My understanding still is that the current tyre pressure values are taken for a reference point, the warning is given once the tyre pressures go lower than this by a certain amount (percentage), with one exception to be discussed later. Another interpretation would be that the TPMS system assumes the tyres are at the fuel-filler flap values and the TPMS reading is calibrated at reset to show those values. The latter interpretation can be shown incorrect with a simple test (I've done this with my Beru system, I cannot do it with the Siemens system as my W221 does not have RDK, just RDW). If you inflate tyres more than advised and reset TPMS, the IC reading would show the actual tyre pressure values instead of the fuel-filler flap values (again within the sensor's accuracy, which is pretty good).
Inspired by your references to the US legal requirements I had a visit at Star Diagnosis computer. I know the sensors have no version coding or parameter adaptation etc. But I had a look at the procedure of changing the TPMS control module. The point is that this same part number is used on different vehicles and in order for the system to take care of the legal requirements, it would need to know the fuel-filler flap figures. Guess what, there are parameter adaptations including the setting for target tyre pressure values for the front and the rear axle independently (no calibration of individual sensors, those are calibrated at production and do not need any follow-up).
I conclude so far that the fact that the TPMS system is aware of the tyre pressure values assigned for the car (at least the current Siemens system, I did not check the same for the Beru system).
The car manual text sounds conflicting with the above. I'm assuming it actually isn't. I'm assuming the calibration by IC reset really taking the current tyre pressure values as the nominal values from which tyre deflation by a certain value (percentage) is detected. This all with one exception, if the tyres are inflated to a lower value than that reading on the fuel-filler flap, the current reading would not be taken for a reference value (even if the manual does not mention any exception, exceptions like would make the manual unnecessarily confusing).
It would be relatively straightforward to test if the above is correct by calibrating tyres to a very high value on one hand and testing the gauge reading where a warning is given when one tyre is deflated. I'm assuming a warning is given at a way higher value than if the calibration was done for correct tyre pressures. Another test should be done at significantly too low tyre pressure values. An immediate warning should appear in this case.
I'd conclude that I was both wrong and right previously: The current tyre pressure values are taken for reference by TPMS if tyres are inflated at least to the values declared by the manufacturer. Otherwise the programmed value is used (this equals the values on the flap). Whoover and others, do you see it differently?
I still have to refresh my memory for the workshop documents. It is easy to spot some new stuff when knowing what to expect.
Edited: I had a look at the workshop documents, I'll edit the info in, the thread really does not deserve a bump.
I guess one point for different views was the comment that the Siemens TPMS automatically learns new tyre pressure values. GF4015P000102SX specifically states that "In normal application cases (wheel exchange or the driver adjusts new pressure values) filling detection automatically determines new specified (reference) values. "Filling detection" occurs if no pressure change (temperature compensated) occurs within monitoring period and tire pressures are above the minimum for the model series.
I would conclude that the workshop documents clearly cover the "self adaptation" for reference pressures. In all typical scenarios the manual activation should not be necessary (it should be done and is also well covered by the documents). There is a minor hint to the SDS calibration when the minimum allowed tire pressure for the model series is mentioned.
Previously I was "complaining" that the autonomous pressure reference adaptation doesn't make sense but since the car is using certain "plausibility" checks and taking into account that the new system is not able to warn for sudden pressure drop (only "rapid"), I guess this makes sense after all. Fully manual operation would be better for an experienced driver but not good for an average driver).
Last edited by Diesel Benz; 06-29-2008 at 05:57 AM.
09-24-2009, 03:53 PM
#18
I have been having issues with my tire sensors on my 2008 S550 w/ AMG package (19" wheels). The tire pressure was set at 39 psi, and the ride too hard for my liking. I lowered the tire presssure to 34psi, and have reset the pressure warning on my dash.
But I still constantly get warnings about my tire pressure. Is there a way to fix this?
But I still constantly get warnings about my tire pressure. Is there a way to fix this?
09-25-2009, 02:06 AM
#19
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I have been having issues with my tire sensors on my 2008 S550 w/ AMG package (19" wheels). The tire pressure was set at 39 psi, and the ride too hard for my liking. I lowered the tire presssure to 34psi, and have reset the pressure warning on my dash.
But I still constantly get warnings about my tire pressure. Is there a way to fix this?
But I still constantly get warnings about my tire pressure. Is there a way to fix this?
Do you get the warnings also if you inflate tyres to a higher pressure? Do the warnings appear randomly or mostly in the morning when tyres are cold?
05-16-2014, 01:05 AM
#20
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2008 S63
Will this reset procedure ALSO reset and update the curent positions of the sensors? I just threw my 20s back on and the tire shop must have swapped over the sensors incorectly. My rear wheels are reading opposite of each other. The rear passenger is actually the rear driver side. I found this out by adding some air today. Will I need to swap the sensors out? Or is there a reset procedure that will correct this for me?
