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CEL Transmission Code 087 500 Oil Pressure Sensor D has Electrical Fault (Stored)
Hi all,
So I just bought a 2016 AMG GTS Edition one which I absolutely love. After driving it around for the day I decided to take it for a touchless wash (stupid I know) there was no wash to the under carriage or engine bay but the jets are fairly strong. Almost immediately after coming out of the wash the CEL tunred on. I drove around for a bit and there were no issues at all with the car. I then parked for the night and took it to our resident merc expert who spent 5 days trying to resolve the problem to no avail.
I have collected the car today with the CEL still on and the mechanic gave me the following code under transmission 087 500 Oil Pressure Sensor D has electrical fault. The mechanic has called all his contacts and even checked the Mercedes database and no one has ever come across this.
Does anyone have any ideas. I have it booked in with the dealer to look at on Saturday but the dealer here in Dubai isnt great so I dont have much hope of them solving it.
Diagnosing faults online is a crapshoot at best, especially since a tech has already looked at it and failed.
A P0875 - Transmission fluid pressure sensor/switch "D" circuit fault - can have either (or both) a mechanical or an electrical failure. With a generic diagnostic here are the possibilities:
The transmission fluid is too low
The transmission fluid is dirty
Bad gasket or components causing a transmission fluid leak
The transmission is overheated
The engine is overheating
Shorted/frayed wiring
Corroded or broken connectors
The transmission pump is faulty
The transmission fluid pressure sensor is faulty
The transmission fluid temperature sensor is faulty
The TCM is faulty
Internal mechanical failure
Given where this happened and under the conditions which you described, and especially since a tech has already tried and failed to solve it, I'm going to try an educated guess that the problem is not any of the possible mechanical failures. I've underlined the two areas in the list above where there is a higher probability the issue lies.
Cables, signaling, opens and shorts are difficult to find. But since you describe there are no signs the car drives poorly or is not in limp mode, the most likely cause for me is a lost +5v signal in/out of the pressure/temp switch.
In short, nothing mechanical has failed, the electrical side of the system has failed.
Diagnosing faults online is a crapshoot at best, especially since a tech has already looked at it and failed.
A P0875 - Transmission fluid pressure sensor/switch "D" circuit fault - can have either (or both) a mechanical or an electrical failure. With a generic diagnostic here are the possibilities:
The transmission fluid is too low
The transmission fluid is dirty
Bad gasket or components causing a transmission fluid leak
The transmission is overheated
The engine is overheating
Shorted/frayed wiring
Corroded or broken connectors
The transmission pump is faulty
The transmission fluid pressure sensor is faulty
The transmission fluid temperature sensor is faulty
The TCM is faulty
Internal mechanical failure
Given where this happened and under the conditions which you described, and especially since a tech has already tried and failed to solve it, I'm going to try an educated guess that the problem is not any of the possible mechanical failures. I've underlined the two areas in the list above where there is a higher probability the issue lies.
Cables, signaling, opens and shorts are difficult to find. But since you describe there are no signs the car drives poorly or is not in limp mode, the most likely cause for me is a lost +5v signal in/out of the pressure/temp switch.
In short, nothing mechanical has failed, the electrical side of the system has failed.
Hey,
Thanks for getting back to me and the detailed response. I appreciate it is guess work online but just wanted some ideas mostly to alleviate my sleepless nights. This was very helpful and much appreciated.
Something I should have mentioned (but it was too early in the morning when I wrote), did the tech try deleting the code? And, if so, did the fault return? And how fast did it return? Immediately, or after warmup and or a drive?
Lots of times when faults like these are set, the system design defaults to an alternate algorithm. If it does, then deleting the code (assuming there is no permanent fault) will reset and allow the primary logistics to be active again.
One scenario in my mind (and probably me just being too creative) - the rush of water from the car wash flooded a connector that caused a temporary dropout on the TPFS output signal or input voltage when you started up after the wash. Even though the connector might have eventually dried out, with the fault code set, it won't go away on its own
To my first question about deleting the code and seeing if the fault returns:
If the fault reappears immediately with ignition on or immediately after engine startup, then the possibilities are:
Lost +5v input to the sensor; "unpredictable/unexpected" output voltage coming from the sensor - here you could have a wiring issue, connector failure, sensor failure as the circuit failed the diagnostic startup.
If the fault reappears only after warmup and after a certain amount of time/driving, the the only possibility for me is a failed sensor itself.
Something I should have mentioned (but it was too early in the morning when I wrote), did the tech try deleting the code? And, if so, did the fault return? And how fast did it return? Immediately, or after warmup and or a drive?
Lots of times when faults like these are set, the system design defaults to an alternate algorithm. If it does, then deleting the code (assuming there is no permanent fault) will reset and allow the primary logistics to be active again.
One scenario in my mind (and probably me just being too creative) - the rush of water from the car wash flooded a connector that caused a temporary dropout on the TPFS output signal or input voltage when you started up after the wash. Even though the connector might have eventually dried out, with the fault code set, it won't go away on its own
To my first question about deleting the code and seeing if the fault returns:
If the fault reappears immediately with ignition on or immediately after engine startup, then the possibilities are:
Lost +5v input to the sensor; "unpredictable/unexpected" output voltage coming from the sensor - here you could have a wiring issue, connector failure, sensor failure as the circuit failed the diagnostic startup.
If the fault reappears only after warmup and after a certain amount of time/driving, the the only possibility for me is a failed sensor itself.
The tech told me they had tried everything to reset the fault including hard reset but it instantly came back. The light only actually comes on once I start the car up.
I am going to see what what dealership comes up with but will try and flag these issues if they come up with nothing.
What is the potential impact of driving the car with this type of fault?
So, last first, I cannot advise you one way or another on driving it as no one past factory engineers completely understand how the EMS is constructed. Even factory techs are only working at the "how or what to do" level and not the "why". A couple of things might make you personally feel better about driving - is the check engine light solid or flashing? If solid, and it was my car, I'd drive it. If it's flashing or restricted performance or both then the system is telling you it NEEDS the trans temp/pressure input to operate.
Just common sense, if the car is performing normally with normal driving, and none of the mechanical issues for a P0875 are present, probably no issue at all with driving normally. Obviously, on a performance car like this one, one that potentially could be tracked, then trans temps/pressures become critical. Maybe under those conditions a solid check engine light would turn to a blinking one. I'm pretty convinced this is a signaling issue in/out of the sensor including the sensor itself. It could be a failed ECU if the tech continued to hard reset it, but in my mind that would be WAY out there and too coincidental.
Something that I would try if this were mine, and if you do decide to drive the car, I would like to know - If you switch to the AMG screen when you start up, please note and monitor the trans temp. See first if you get any startup temp and does it progressively rise as you're driving?
That would be this screen:
Last edited by Acta_Non_Verba; 02-18-2021 at 01:16 PM.
So, last first, I cannot advise you one way or another on driving it as no one past factory engineers completely understand how the EMS is constructed. Even factory techs are only working at the "how or what to do" level and not the "why". A couple of things might make you personally feel better about driving - is the check engine light solid or flashing? If solid, and it was my car, I'd drive it. If it's flashing or restricted performance or both then the system is telling you it NEEDS the trans temp/pressure input to operate.
Just common sense, if the car is performing normally with normal driving, and none of the mechanical issues for a P0875 are present, probably no issue at all with driving normally. Obviously, on a performance car like this one, one that potentially could be tracked, then trans temps/pressures become critical. Maybe under those conditions a solid check engine light would turn to a blinking one. I'm pretty convinced this is a signaling issue in/out of the sensor including the sensor itself. It could be a failed ECU if the tech continued to hard reset it, but in my mind that would be WAY out there and too coincidental.
Something that I would try if this were mine, and if you do decide to drive the car, I would like to know - If you switch to the AMG screen when you start up, please note and monitor the trans temp. See first if you get any startup temp and does it progressively rise as you're driving?
That would be this screen:
The light is solid and a never changed colour or blinked.
I usually drive with the AMG screen in front of me as I like looking at the metrics.
Car starts out at arojnd 25C and then holds stead around 100C whje driving normally on comfort but can go up to 115 ish when driving on sports +. I am starting to think more and more that this is an electrical issue and the first tech that had a look wasn't thorough enough.
I've been thinking more about your situation and, as an afterthought, it occurred to me this happened to you at a car wash. Based on the way you described the car wash and water pressures, there is a possibility you've had water ingress via clogged drain holes. If that happened, and based on the severity, electrical damage of varying degrees is a known result. Owners in past threads have reported issues with this. I did a quick search and came across a couple of threads, but a better effort might produce more. Additionally, owners of roadsters appear to have had more severe issues than coupes.
Very sorry if this is the cause of the CEL after the carwash as water ingress around the boot could have flooded a connector midstream in the harness and a reason the techs cannot make sense of the problem. These are very difficult to find and sort, unfortunately.
Not a problem exclusive to this car either. Bentley GTs were plagued with a similar issue. clogged drains caused water ingress in some very bad places, one of which would put the two ECUs under water. In these cases, sometimes the entire main ECU harnesses needed bypasses and ECUs replaced. I washed my Bentley by hand, as well as this one and use water very sparingly.
Same here. CL63 driver rear plastic wheel well actually used rivets and during wet driving it seeped into the electronic tub that housed everything. Over 15k worth of boxes. Drain tube was blocked.
Today, you might already have your car in the MB dealer, but since there is a possibility your car suffered from a failing drain system at the car wash I thought it could be helpful to you if they know what to look for at the rear drain system, and they probably do.
The first sign the rear drain system failed, especially if there was a catastrophic flood of water is any signs of water or wetness in the hatch floor (tub). Second, when the drain system fails, water fills the hatch door and the only outlet is the hinge latch area. So look for signs that water flowed around the tailgate hook and the mating latch. Here are pics of mine. My drains are functional so there are no telltale signs that water was present (look for dried water spots):
Upper "hook" in the tailgate:
Lower mating latch:
The lower latch opening is where water enters and causes electrical damage when the drain system fails. This latch should be bone dry after any car wash or heavy rains.
If the drain system failed, there are some key areas that either, by themselves, or in combination, will cause water to be where you don't want it. First, let's talk about the left and right drains and how the system is plumbed.
The right side drain outlet at the underside of the tailgate is a straight tube to the drain in the right side hinge well to the spoiler.
Here is the drain outlet:
Here is the spoiler hinge pocket drain:
The left side drain outlet is a little more complex. It too is connected (via tubing) directly to the left side spoiler hinge pocket drain, but the CENTER tailgate drain is "TEED" into this pipe.
Left side drain outlet:
The left side hinge pocket drain looks just like the RS so I'll save that pic, then the center drain under the spoiler is this one:
That covers the drain piping system in the tailgate and free from any obstructions and clear, it is designed to remove any water that floods the spoiler area and directs water to the left and right corners of the tailgate, onto and over the rear bumper.
There is a secondary issue that, even with clear and working drain pipes, flooding of the tub and damage can still occur. These are plugs that must be in place on the left side and right side spoiler hinge pockets.
In this pic, I've removed the left side plug and shows the hole (opening) in the hinge pocket. So, if this plug is missing, even with a working drain in this hinge pocket, if water rushes in and fills this pocket, then water will end up in the tailgate and drain in the same place, the center hinge and into the tub.
Left side plug out:
Right side plug in place:
So, for maintenance of the rear hatch drain system in a GT,
1. First, make sure that both the left side and right side hinge pocket plugs are in place.
2. Using compressed air (and I'm going to shout here) WITH VERY LIGHT PUFFS OF AIR USING A BLOW GUN, check to see if the right side drain outlet and the right side hinge pocket drain flows clear. I stress using light puffs of air BC too much pressure and the potential of blowing the plastic tubing off inside the tailgate is possible. Then you'll be disassembling the tailgate to reinstall. My compressor is set to 90psi and I estimate I am using about 8 to 10 psi MAX.
Right side and the simple plumbing side:
3. With the left side and because this side TEES to the spoiler center drain, use the blow gun to clear in two places. First, Clear the center drain using light puffs of air.
Doing this should produce air at both the the left side hinge drain AND the left side tailgate drain outlet.
4. Then, use compressed air at the left side tailgate drain outlet and air should come out at both the left side hinge drain AND the spoiler center drain.
If you take all of these steps and make these inspections on a regular basis (maybe once or twice a year) these rear drains should function properly and prevent any catastrophic electrical damage in the rear electronics. REMEMBER, when you do the light puffs of air on the left side and the right side, the air MUST come out of the outlets described above. If you use light puffs of air and DO NOT feel the air coming out of the outlets as described above, then it probably means that either the tubing is disconnected inside the tailgate, or cracked and leaking. Either of these conditions is the same as the drains not working correctly and water WILL enter the tub via the tailgate hinge assembly.
Hopefully you'll see this before bring your car in today or if the MB dealer gets stumped and this is the issue.
I've been thinking more about your situation and, as an afterthought, it occurred to me this happened to you at a car wash. Based on the way you described the car wash and water pressures, there is a possibility you've had water ingress via clogged drain holes. If that happened, and based on the severity, electrical damage of varying degrees is a known result. Owners in past threads have reported issues with this. I did a quick search and came across a couple of threads, but a better effort might produce more. Additionally, owners of roadsters appear to have had more severe issues than coupes.
Very sorry if this is the cause of the CEL after the carwash as water ingress around the boot could have flooded a connector midstream in the harness and a reason the techs cannot make sense of the problem. These are very difficult to find and sort, unfortunately.
Not a problem exclusive to this car either. Bentley GTs were plagued with a similar issue. clogged drains caused water ingress in some very bad places, one of which would put the two ECUs under water. In these cases, sometimes the entire main ECU harnesses needed bypasses and ECUs replaced. I washed my Bentley by hand, as well as this one and use water very sparingly.
Thanks for this and the walkthrough, the car is currently with the dealer so will ask them to look into this once they get back to me later today with a diagnosis (or not) to the issue. I am hoping this doesn't turn out to be the case though. Will keep the thread updated as I find out more.
Day 3 at the dealership and still no resolution to the issue. There seems to be some.progress as they have managed to get the light to turn off for a bit after reprogramming but came back on after a short drive. They then cleaned the cam shift position sensor and the light came back on after 20 minutes of idling. Seems like the local merc expert is now involved abd asking them to do additional checks to the transmission.
It doesn't seem like there is ever going to be an end to this .
It now appears to be that they have identified an issue with the electrics in the gear box and the oil pressure sensor, the dealer is saying that this would require a full replacement of the gearbox which seems crazy to me! Has anyone experienced this?
It now appears to be that they have identified an issue with the electrics in the gear box and the oil pressure sensor, the dealer is saying that this would require a full replacement of the gearbox which seems crazy to me! Has anyone experienced this?
It's because dealers are not allowed to fix anything on that transmission yet, they can only replace under MB's rules for dealerships. I'd continue to push for a diagnose and not just a replacement and see if it works.
Day 3 at the dealership and still no resolution to the issue. There seems to be some.progress as they have managed to get the light to turn off for a bit after reprogramming but came back on after a short drive. They then cleaned the cam shift position sensor and the light came back on after 20 minutes of idling. Seems like the local merc expert is now involved abd asking them to do additional checks to the transmission.
It doesn't seem like there is ever going to be an end to this .
Originally Posted by Gonik
It now appears to be that they have identified an issue with the electrics in the gear box and the oil pressure sensor, the dealer is saying that this would require a full replacement of the gearbox which seems crazy to me! Has anyone experienced this?
Hani,
Well, glad they're finally making progress. Seems like once they got the system to stop failing on startup diagnostics, then the real issue started to show up which is what I meant in the last line of post #4. With all sensor inputs in modern EMSs, the expected output ranges are known and programmed as part of the algorithms. So, as things start to warm up, the pressure sensor should be delivering a predictable voltage and compared to the voltage expected. If it doesn't, then that sensor is probably failing or failed. If it was wiring that created an open or short, that would continue to fail at startup diagnostics. The sensor is the only thing left.
Also, everything is housed inside the box in these units. ZF xHPxx trans uses the same design, even the TCM is internal.
One thing about trans replacement, if it is not under any warranty and at your cost, inquire if there is a core refund for your unit. These units are hardly ever scrapped, they send them back to the supplier or a rebuild center and it will be resold. A core refund will help mitigate costs if you are paying.
They have gone back to Mercedes Germany with the question as to whether they would be allowed to only change the Hydraulic Control Unit. I am not able to find much about the cost of this online so am unsure how much this whole thing is going to run me.
I can't help but think the guy I bought this car off of 2 days before the light came on knew about this issue.
I am going to push for an exact diagnoses and likely take it elsewhere to fix. As always advice is appreciated.
Any updates to this? Did you end up replacing the entire transmission? Did they get to the bottom of the CEL?
Turned out to be a failed Hyraulic Control Unit which mb Germany approved to be replaced rather than the full transmission replacment. Works are still ongoing but I has run me upwards for 10,000 USD so far.
Turned out to be a failed Hyraulic Control Unit which mb Germany approved to be replaced rather than the full transmission replacment. Works are still ongoing but I has run me upwards for 10,000 USD so far.
Will update when works are complete by next week.
Holy... How did it fail? Did they narrow it down to failure due to the carwash, or just failure due to age? I also have a 2016 amg gts and these are the nightmares I have about this car!
Holy... How did it fail? Did they narrow it down to failure due to the carwash, or just failure due to age? I also have a 2016 amg gts and these are the nightmares I have about this car!
They have no idea, they say it is just a parts failure using the excuse that I "missed" a service. It has nothing to do with the wash apparently. I think I've just been unlucky car has been in various shops for 2 months and now with the dealer I could have probably done it elsewhere cheaper but don't trust people on tramission work here in Dubai.
They have no idea, they say it is just a parts failure using the excuse that I "missed" a service. It has nothing to do with the wash apparently. I think I've just been unlucky car has been in various shops for 2 months and now with the dealer I could have probably done it elsewhere cheaper but don't trust people on tramission work here in Dubai.
Do you know if the previous owner launched the car or drove it hard? Since you are in Dubai maybe the high temperature accelerates the wear and tear on the transmission modules?
02-18-2021, 01:16 AM
CEL Transmission Code 087 500 Oil Pressure Sensor D has Electrical Fault (Stored)
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