I had my summer tires mounted and now the TPMS inoperable light is on.
Story below.

Had Firestone mount my new summer tires to my summer wheels on which the tire sensors had been working fine (drove them for a few dayss with the old tires).
Two days later, I get the "inoperative" message. I had not checked it after picking up the car at Firestone. So, I don't know if it was displaying the pressure of the four tires before the warning came on.

Yesterday, I took the car to the dealer. They pull the tires, they blamed the aftermarket schraeder sensors which had been working. I bought these the prior season from TPMS.com. The MB dealer inspected them, says one of them isn't working and found no physical damage. They'd recommend installing OEM sensors at great expense. I declined.

I took the car this morning back to Firestone. They have an electronic tool that senses whether the sensors are broadcasting. I went with the technician out to the car. When he held the device to the sidewall of each tire, I saw for myself that the sensor broadcasted the frequency and the correct tire pressure. I made an appointment to come back later in the week.

I went home, thinkinmg I could figure out how to have the sensor unit relearn the position of the sensors in the wheels, I tried again resetting the system. Perhaps I'm doing it wrong?

1) I had the ignition in the 2nd place in the "on" position (without the engine running),

2) pushed the arrows on the steering wheel until I got to the odometer,

3) scrolled to tire pressure,

4) clicked it, got to the "inoperable" warning message.

5) pushed the OK button. The "inoperable" message remained. This is the point I'm stuck.

Is there another way to reset the TPMS system?


Firestone says that they likely changed the position of one of the rims from the right side to the left or the other way around.


But there is a TSB (see below) for this warning for the 204 models. Is a W212 year 2012 a model 204? Still, the problem started with a tire change.

Does anyone have a suggestion?

opic Number LI40.15-P-046651

Version 1

Design Group 40.15 Tire pressure/tire pressure monitoring

Date 09-24-2009

Validity Model 171.454/456/458/473
Model 204.054/056/077/081/956/987

Reason for change:Instructions revised foe Xentry/Supersedes DTB S-B-40.15/68
Reason for block
Complaint:
Display Message "Tire pressure Monitor Inoperative" DTC 5581
Cause:
If you receive customer reports in the above model vehicles of the instrument cluster displaying "Tire Pressure Monitor Inoperative" and there is a corresponding stored fault code of 5581 (front or rear sensor localization failed), this is because the difference in the signal strength between the front and rear axle may not be enough for the wheel assignments to be accurately made.

 

Could it be the battery in the TPMS is dead?

 

Firestone got the TPM system working. They reprogrammed the computer with the Identifying code for each sensor. They used the OB port.

 

That's great to know. It's good you refused to buy the oem TPMS for double the price.