tunafish

I recently began seeing the message on my speedo screen saying, "Tire Press. Monitor Inoperative". It is intermittent. I have been to the dealer once about this, and they can't find anything wrong. It is not a problem with pressures, but obviously either a problem with one of the senders or the receiver. Anyone else have this problem?

maverickvii

I had this issue too for quite a while. It was especially annoying because even when I would clear the message the tire pressure indicator stayed illuminated. I checked the pressures and then of course as soon as I made an appointment with the dealership, the problem just went away.

Can't help you but I feel your annoyance.

tunafish

I got a call from the dealer. There is a MB technical bulletin on this. The dealer is replacing a wiring harness in the trunk area. Apparently there is a grounding problem. I'll let everyone know if this works.

tanktube67

Keep us posted.

nyca

I had this problem - one of the sensors had fallen off into the wheel.

dansonchan

Me too... did search in eBay,saw $55 something tpms as same as mercedes tpms! Doesn't it fit?

dansonchan

http://cgi.ebay.com/ebaymotors/ws/eB...T#ht_675wt_948

Ron Jr

Just order one from Tire Rack I know they work from there I have two sets.

tunafish

Replacing the wiring harness didn't help. Then they replaced the TPM receiver somewhere behind the dash. That didn't help.

I suppose they will now replace the sending units in the wheels, which probably would have been the simplest, cheapest thing to do in the first place.

Oh well...

RLE

Must have been something else because as long as the sensor is inside the tire, it's still reading the pressure.

This happened to my car when it was new and the dealer installed my Bridgestone tires and the "tech" broke the sensor off with the tire mounting machine. It was clunking around in there for a week or so causing balance problems but no warning lights.

tunafish

So, now they are telling me that the aftermarket backup camera I installed (see cyclops thread) is causing the TPM to fail. Despite the fact that the TPM worked fine for the 1st 7 weeks I had the camera. And the fact that a zillion people have done this camera install and no one has a problem with TPM.

This isn't just local service people... the MB tech gurus are telling the local techs this. They don't know what they are doing, so they fall back on the lamest excuse possible.

tunafish

Well, they were right after all. The backup camera was causing the TPM to fail. There were actually 2 problems (I think). The guy that installed the camera did not use a continuous shielded cable from the FAKRA connector to the camera. He cut and soldered the cable, leaving a break in the shield. This allowed RF noise from the TV scan to leak out and interfere with the TPM. The problem did not show up as long as the camera was only powered on when the car was in reverse, but I had the camera rewired to be on whenever the ignition was on to avoid a synch problem. This caused the RF interference to be present whenever the car was running. When we disconnected the camera system, the TPM problem went away. My apologies to MB.

maverickvii

Wow as you were posting I totally agreed with you that the camera was a lame excuse by MB. Insane that it ended up being the actual problem. Are you going to end up adjusting the camera system to be usable?

tunafish

Not right away. If I do, I will replace the entire cable with a fully shielded one, and set the camera to be powered by the backup lights again.

I may wait until the warranty runs out, given that the dealer spent a week diagnosing the problem and didn't charge me anything.

RLE

My backup camera, installed by me following the directions, has been working for three years with no problems.

tunafish

I'm not surprised that most people do not have any problems. I made 2 mistakes; 1) leaving a break in the shielded wire carrying the video signal which allowed RF to escape, and 2) wiring the camera so that it was powered all the time the car was on. My problem was likely due to this combination of mistakes. If the camera is only on during the few seconds you are in reverse, it is unlikely to produce interference long enough to cause a TPM fault. If I had used a continuously shielded cable, it probably wouldn't have mattered.

Dark Kent

My car has this problem and I just got it a week ago. I have a bubble on 1 tire and I'm still waiting on the dealership to order a new one for me so I was kinda hoping that was causing the problem.

EnigmaAW

i had the TMPS inoperative warning issue too, the dealer blamed it on my 22's which have been mounted for almost 2 years prior. they said the valve stem does not stick out enough and it's causing the problem. which really does not matter becuse the sensor is on the back side if the valve stem? the light came for about a week, i took it to the dealer, they cleared the warning. and said if i put my factory 20's back on it won't have the warning come up anymore. it came on for 2 days after i left the dealer, then went off and has not come back on for 8 months now. I think it was just a glitch?