Tire Pressure Monitoring System (TPMS)

[cholm]

Long Post:

Having spend a lot more time sorting this out than I wanted, but after reaching a successful result, I decided to spend a little more time and share what I learned.

First, if your SL500 has TPMS and you have not already had to replace some or all of the sensors in your tires/wheels, you eventually will. As far as I can tell, Mercedes has not installed any sensors that are not battery powered. All batteries eventually die and those in our tire pressure sensors appear to have a life that runs out at about 5 years. If you get more time, you are probably just lucky.

Second, getting the correct sensor for your car is not easy, and even the dealers seem to have problems matching the correct sensor to the car.

At a minimum, you will need your VIN to determine which option codes were installed. The codes of interest are these:

model year, or YOM (this starts with an 8 and as 2 more digits) e.g., 805 is 2005, 806 is 2006.
Tire pressure monitor system (470 or 475) 470 is low line, 475 is high line/mid line
You also need to know whether your car has some other options, such as:
494 - US version
761 - Radio Remote w/ reduced range w/o panic switch 315 Mhz
762 - Radio Remote w/o panic switch 315 Mhz
763 - Radio Remote w/ panic switch 315 Mhz
P99 - AMG Signature Black Special Edition

Finally, you need your chassis number.

Then, you, your independent or the dealer will need to match that information to the following: This is a list from EPC net of the sensors that might go in a 230475 (i.e., US SL500).

First, determine whether your car is YOM 805 or 806.

Except 806 (i.e., this should include 805 and earlier)

A000 822 33 06
433 Beru
To 109634 to 31/05/2005
475

A000 822 48 06
315 Beru
To 109634 to 31/05/2005
475 + 761

A000 822 34 06
315 Beru
To 109634 to 31/05/2005
475 + 494 / 475 + 762 / 475 + 763
(print out of control unit required)




Except 805, presumably this would include 806 and later

A002 540 48 17 (replaced by A002 540 67 17)
433 Siemens
From 099797 from 13/01/2005
470 / 475

A002 540 67 17 (replaced by A002 540 69 17)
433 Siemens
From 099797 from 13/01/2005
470 / 475

A002 540 69 17
(not stated, prob 433 since that is the prior)
From 099797 from 13/01/2005
470 / 475
(print out of control unit required)

A002 540 47 17 (replaced by A002 540 66 17)
315 Siemens
From 099797 from 13/01/2005
To 130294 to 31/10/2006
470 + 494 / 470 + 762 / 470 + 763
475 + 494 / 475 + 762 / 475 + 763
(print out of control unit required)

A002 540 66 17 (replaced by A002 540 68 17)
315 Siemens
From 099797 from 13/01/2005
To 130294 to 31/10/2006
470 + 494 / 470 + 762 / 470 + 763
475 + 494 / 475 + 762 / 475 + 763
(print out of control unit required)

A002 540 68 17
315 (mfgr not stated)
From 099797 from 13/01/2005
470 + 494 / 470 + 762 / 470 + 763
470 + 494 + P99 / 470 + 762 + P99 / 470 + 763 + P99
475 + 494 / 475 + 762 / 475 + 763
(print out of control unit required)

A002 540 79 17 (ersatz fuer A002 540 68 17, I think this means replacement for)
not stated, (prob 315 Mhz since that is what A002 540 68 17 says)
470 + 494 + P99 / 470 + 762 + P99 / 470 + 763 + P99
(print out of control unit required)
Interestingly, this part number seems to replace A002 540 68 17, which says it applies to 475 + 494 / 475 + 762 / 475 + 763 and 470 + 494 / 470 + 762 / 470 + 763, but those don't show up for this part. Further, the to/from chassis number and dates are not provided for this part. All very confusing.

According to my data card from EPC net, my 2005 SL500, chassis number about 91000 (805, 494, 763), should use A000 822 34 06.

My local independent MB shop uses EPC but when he saw all the possible part numbers, he didn't want to risk getting the wrong sensor, so he called the local MB dealer, gave them the vin and asked for 2 replacement sensors. (Somehow he was able to read out the system and determine that the other two sensors have 20+ months useful life left). The dealer sent over two A002 540 79 17 sensors. The shop installed them, but was not able to get the system to re-set and correctly read the pressures. The system did appear to somehow detect the sensors, because it didn't immediately error out.

I took the car home that night anyway and tried to reset the system 5 times over the weekend, allways with the same result. I also spent a huge amount of time trying to figure out whether the sensors that the dealer sent over (A002 540 79 17) might be wrong. It appeared to me that either the newly installed sensors were 470 only, when my car needed 475, or even if they worked with 475, maybe they would not work because my car is YOM 805. I took all my research back to the independent to show him my suspicions. He was as confused as I was, and called the dealer again. Someone else did some additional research and came back with a different part number. That number was A005 ??? ?? ??.

I took the car back to the independent yesterday, he installed the two A005 sensors, and everything reset and it works as it should.

Morale of the story, At least for 2005 and 2006 SL500, get the sensors from the dealer rather than from an after-market mfgr. Also, get the dealer to research the correct sensor and also get them to check for updated sensors (the A005 part number that eventually worked didn't even come up on EPC net). Finally, if the dealer isn't installing them, make certain the dealer will swap them out if they make a mistake and give you the wrong sensors.

BTW, my independent is Herbert, at German Motor Car Service in Santa Monica. Great guy, great reputation, only Mercedes and a pleasure. Not really cheap, but I know he is a better mechanic than the local dealers. (When I was first trying to resolve this problem, one of the service writers at the MB dealer near down town LA told me that the wheel sensors seldom go bad, almost as though he didn't know there were batteries in them that die. I could imagine that his solution would be to change out the control unit first. I don't think he even knew that they can read out the life of the sensor from STAR) .

Chris

[lkchris]

TPMS wasn't really required until 2007 model year, so most of those are still ok and there probably are very few cars from prior years with the system installed. SLs in general are pretty "rare" of course. It could also be but I'm not sure that battery life for earlier systems is less than that for current systems. In any event, your SA will be learning more shortly!

[purefct]

Last month I had to replace 3 of my 4 sensors, paid to replace all four since I have a 2004 SL500. 1 Sensor had an electrical failure rather than the other two with batteries dead so my extended warranty covered it. I still forked out just over $1,000 for the three but my dealer gave me a 15% discount on another $400 work which was performed as well.

BTW, a pulley froze, causing my belt to break, which slashed a lower radiator hose. Pulley replacement $155 (covered by the extended warranty) but the belt and hose ran $400 which was not covered by my warranty. No colateral damage is covered and belts/hoses aren't covered!

[okbarnett]

these internal tpms sensors are about $99 ea at allmercedes.com or Hendricks mercedes where I buy almost all my parts

[purefct]

That's a great website, so you bought the calibration equipment and calibrated the sensors to the controller? I'd like to borrow some of that!

[purefct]

In retrospect, my last post sounds excessively sarcastic. I really do like allmercedes.com - just not certain how to take a comment about how you can buy 4 sensors for under $400 without acknowledging any importance for the tools and skill required to calibrate the parts to function correctly. I'm an avid do it yourselfer and in this economy have begun working on my own cars again. But TPS is more than an advanced home mechanic task.

[bsegan]

The system is bullshit anyway. It's not like it's giving you an exact readout inside the car of the tire pressure, which would actually be useful. Oh look, a light letting me know it's low, since in the last hundred years no one has used a manual gauge to check the pressure on a regular basis.

[purefct]

While I agree the readout might not be exact, the TPS on my 2004 SL500 shows specific tire pressure for each tire. In general though, the pressure is accurate. My SL has a diagram of the car with pressure readings at each tire location, but I did Google around and there are indeed some tire pressure systems which merely provide the warning. The other threads I read where TPMS was addressed were Canadian/European members and I think the primary system providing a warning was called RDW? I closed the threads, sorry. Anyway, not sure why so many people post the TPMS is a warning only, I have the car diagram with specific readouts on my instrument cluster. Let me know if you want to see a pic!

My system, as I understand it, doesn't merely signal low pressure, it signals when the pressure falls more than a certain amount, I think 3-7 psi, for any specific tire. Since I watch my pressure periodically I rarely get the warning anymore as I am already adding air.

[bsegan]

Picture...I am surprised MB would remove that sort of readout, which is actually useful, and replace it with a blue screen 'please adjust tire pressure' reminder and a red screen 'Check tire pressures' warning that exists in my SL550.

My only thought would be back in '04 TPMS could have been an option of some sort, which I believe was still before it was a government mandate requiring all new cars to have some notification for low tire pressure, and when it became a requirement (I want to say 2007 from memory) that they just went with a low cost option since it had to go in every car.

[purefct]

That's true, per a conversation I had with my MB Service Dept my 04 TPMS was an option, which of course now that I have it I can't disable (which for over $1,000 to replace sensors every 4-6 yrs I would have disabled).

I'll post a pic a bit later!