Mercedes S class 2007-2010 relearn

Ive had a lot of questions about the Mercedes S class and relearns recently here is a good read to follow:

TIRE PRESSURE MONITORING SYSTEM FAULTS AND FIXES
Most of the information you need about the various warning messages one gets from the Tire Pressure Monitoring System (TPMS) is in the owner's manual. This post will not repeat the steps one takes as explained in the manual. Instead, it will go a bit beyond them.

There are two basic kinds of warnings. The first says "Tire Pres. Monitor Reactivate After Correcting Pressure" OR "Tire Pressure Please Correct." Both of these warnings are the result of incorrect tire pressure. The system is likely functioning as it should. It is also possible that the batteries in one or more sensors in the tires is failing. If you have adjusted tire pressure to the proper inflation, and the message keeps popping up, the problem is probably sensor batteries. If the system cannot be reactivated, or does not come back in on its own after you have set correct inflation, see the W220 S-Class Encyclopedia section on TPMS problems - http://www.benzworld.org/forums/w220...tart-here.html. Replacing sensor batteries requires replacing the sensors, and there are much less expensive alternatives than the dealership.

The other kind of warning indicates a possible problem with the TPMS itself. The warning will say "TPMS is not functioning - Drive to Dealer" or "Tire Press. Monitor Control - Visit Workshop" - the warning varies from model to model and year to year. The bottom line is, it tells you to see the dealer. However, you should first try to reactivate the TPMS using the procedure in your owner's manual. First, be sure your tire pressures are set properly. Then use the book procedure.

The causes of the latter type of warning can be several. The owner's manual mentions several: 1) If you have changed tire inflation pressure; 2) If you have replaced or installed new wheels or tires; 3) Having an underinflated spare tire.

However, experience of many forum menbers has shown other possible triggers: 1) A weak battery; 2) large changes in temperature so that your tire pressures change significantly from where they were when the system was last "reactivated;" 3) On my own system having any tire reach a pressure of 37 psi or higher for several minutes (this was done by a dealer after rotating my tires and overinflating them, and has also happened with wide temperature variations during a single day after the tires had been inflated for very cold temperatures). The 37 psi is not a system specification I am aware of - but the warning happens in my car every time a tire reaches that and stays for more than a few minutes. 4) Having the tire pressures differ from left to right by more than 2 or 3 psi, and remain uncorrected; 5) Having the front and rear pressures differ significantly more than the 3 psi called for by the placard; 6) replacing TPMS sensors and keeping the old ones in the car (probably in the trunk). Last, a failed TPMS controller. Reactivating the system will not fix a failed controller.

In order to reactivate the system, you must do more than just briefly pressing the "R" button on the instrument cluster. Follow the instructions in your manual to get to the "Monitor Tire Pressures Yes/No" menu choice on the multifunction display (MFD). Once you have selected "yes," the message you will get will say "Tire Press. Monitor Reactivated" or similar language; then it will say "Tire Pres. Display Appears After Driving A Few Minutes" or similar. Again, the exact language can vary by year and model car; it is the same message you get if you check the TPMS after starting the engine, but before starting to drive.

If you merely press the "R" button briefly after getting a Drive to Dealer warning, all you do is clear the warning message from the MFD. The system will retain the warning (you can see it if you scroll to "messages" on the MFD, and check what is there; if it says 1 message, it will be the retained warning when you check it). If that happens and you try to select the TPMS display later, you will simply get the warning message again. You will NOT have "reactivated" the system. For my particular model, the "reactivate" feature is reached by pressing and holding the "R" button for 3 seconds, after which the "Monitor TPMS Yes/No" screen option comes up. For other models and years, it may be different.

IF you have inflated your tires to placard (recommended) pressures, you will probably get the tire pressure display within about 5 minutes or less of driving. The more your tire pressures deviate from the recommended pressure, the longer it may take. On the day I got the warning after my tires, which were inflated for colder temperatures, but were driven on an unseasonably warm day, I only let them cool a bit, but did not adjust pressures. It took 20 minutes of driving before the pressure display diagram came up. On the day the dealer overinflated them (after rotation & balance), it would not "reactivate" until I had reduced tire pressure by letting air out.

I cannot explain the messages any better than that. No matter what, the bottom line is, after a TPMS warning telling you to drive to the dealer, use the owner's manual procedure for your model to reactivate the system. If it still won't come back, be sure your tires are properly inflated, and try it again.

For more information on sensor batteries, sensor replacement, and the like, see the TPMS entries in the W220 S-Class Encyclopedia at http://www.benzworld.org/forums/w220...tart-here.html

http://www.benzworld.org/forums/w220...lts-fixes.html