TPMS reading incorrect pressure
Thread Starter
Junior Member
Joined: Nov 2014
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From: Manchester NH
2012 S350
TPMS reading incorrect pressure
New wheels and brand new sensors and my right rear wheel reads incorrect pressure and shows the pressure drops a couple PSI per day. I'd just assume it was a bad sensor but it did the same thing with the stock wheels in the same position, right rear. Thoughts? It's annoying because the warning light comes on and it keeps making me stop and check my tire pressure. I'm running 45 PSI and it currently shows 27 PSI. The car is new to me as of only 2 weeks ago.
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'06 S65 AMG W220 12.31@119_MPH (Stock)
When you say you're running 45 PSI. Are you measuring that with a high quality mechanical dial external gauge? And when your car is reporting 27 PSI. if you check the pressure with the external gauge, does it still shows 45 PSI ?
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'06 S65 AMG W220 12.31@119_MPH (Stock)
I would try a different external gauge preferably a mechanical dial one. I just don't trust those digital gauges sometime. I think it would be easier to get another gauge rather than going through and replacing the TPMS again.
Thread Starter
Junior Member
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From: Manchester NH
2012 S350
It's absolutely 100% not the gauge. Like I said... The decreasing pressure on the readout has caused me to pull into a gas station to check pressure, I checked at my dads house with an old style also. 45 psi each and every time. It can't be the sensor either... Unless I just happened to have 2 bad sensors in the exact same position. I have the same issue with the stock wheels installed.
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'06 S65 AMG W220 12.31@119_MPH (Stock)
There's only 3 suspects, 4 if you count the Schrader valve. The wheel, sensor and tire. You tried different wheel and sensor. I presume you're 100% sure your tire don't have a leak. If your gauge indicate 45 PSI exactly on all 4 tires then just ignore the alert for a while and see how low the pressure on your dash will go to.
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2016 C300
Aren't there two components to the TPMS at the wheel...the TPMS device in the valve stem assembly, which is a little radio transmitter and the sensors on the car to read the output from the transmitters? Or is there one central sensor for all 4 wheels? I believe there's also a way to tell the car to accept as "normal" whatever the settings are at that moment. Not ideal but it would stop the error messages.
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Out Of Control!!
Joined: Jul 2003
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From: North Scottsdale, AZ
'71 Pinto
One control unit (10 in diagram) receives signal from all wheel sensors (110) rear monitoring incorporates an antenna (50). If you purchased from MB dealer request they check for fault codes. If not, have an independent check using MB diagnosis system.
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'06 S65 AMG W220 12.31@119_MPH (Stock)
I'm not doubting that your car is showing low tire pressure. I'm more afraid that's it's telling you the truth. Those TPMS sensors are usually pretty accurate with their readings from my experience with 6 previous cars I've owned with them equipped. Granted, they weren't all MB. That's not to say there wouldn't be a first time that they're wrong.
You said that when you check the other 3 tires, your MAC pressure gauge always shows 45 PSI each and every time. However, your car is indicating 41 for FL, 43 for FR and 42 for RL. Are those other 3 sensors misreporting their readings also? These sensors have a 1 PSI resolution and every PSI counts. I'm assuming you didn't round up the reading and they were actual?
You said that when you check the other 3 tires, your MAC pressure gauge always shows 45 PSI each and every time. However, your car is indicating 41 for FL, 43 for FR and 42 for RL. Are those other 3 sensors misreporting their readings also? These sensors have a 1 PSI resolution and every PSI counts. I'm assuming you didn't round up the reading and they were actual?
Thread Starter
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From: Manchester NH
2012 S350
Thread Starter
Junior Member
Joined: Nov 2014
Posts: 28
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From: Manchester NH
2012 S350
AH HA!!!! Figured it out. The TPMS thinks the left is the right and vice versa. The LEFT rear tire was low... Now they all read correctly. The factory wheels must've just been coincidence.
Thread Starter
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From: Manchester NH
2012 S350
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'06 S65 AMG W220 12.31@119_MPH (Stock)
Congratulations! I'm glad you got it resolved!
I'm just trying to understand this. So the TPMS was reporting the correct pressure but for some reason the Mac guage kept showing 45 PSI for all the wheels?
I'm just trying to understand this. So the TPMS was reporting the correct pressure but for some reason the Mac guage kept showing 45 PSI for all the wheels?
Thread Starter
Junior Member
Joined: Nov 2014
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From: Manchester NH
2012 S350
45 PSI is me rounding off. I didn't think I needed to say LF 43.5 PSI, RF 44.5 PSI etc...
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'06 S65 AMG W220 12.31@119_MPH (Stock)
This is the part I'm trying to understand. If you were reading 45 PSI on all 4 tires with your gauge everytime, what sensor or other gauge finally led you to believe that one of the tire was not 45 PSI?
Thread Starter
Junior Member
Joined: Nov 2014
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From: Manchester NH
2012 S350
I didn't check the pressure (with the gauge) of the all the tires that were reading correctly? I assumed the TPMS was reading correctly except for the tire reading incorrectly.
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From: Georgia
E 63S Wagon Renntech, E55 Renntech, SL65, SL 55 030, ML, bunch of old ones--they come, they go...
I have this same problem with a 212...
LR, even after a new sensor, shows 22 lbs. All orhers are accurate. I assume it needs to be the sds box to check, yes?
