I've been having a problem with a tire pressure warning that shows up intermittently while driving. The tire symbol flashes and message center gives a "tire pressure sensor fault" indication that will eventually clear itself after a few starts.

I do have a full size spare on an '05 factory rim that I am rotating thru the tire positions that does have the sensor installed. My Ford dealer was not able to provide an Eco Plus tire, so I had to purchase it and have the sensor installed at a local tire dealer. I gave them the sensor mounting band and instructions, but didn't verify the installation myself. The problem started after the spare was installed.

I have had the dealer try to check the problem, but they've told me that the alarm is not stored in the computer's memory and their suggestion was to add air. I've also had them reset all of the sensors the last time I had a rotation done, but it hasn't helped.

I am now wondering if the sensor was installed wrong by the tire dealer, but I am hoping for some advice before having the tire demounted. Also, can the sensors themselves be checked to be functioning correctly some other way while still on the car?

Bill, this problem has recently been discussed in great detail. Look here: http://www.greenhybrid.com/discuss/f...roblems-13895/

Post back if you still have questions.

In short the car can only keep track of FOUR TPS sensors. You'll have an error whenever you swap in the spare unless you can get them to retrain the system each time it rotates in/out.

And the dealer won't retrain the system for free, at least mine won't. Perhaps one could negotiate the retraining as part of their $20 tire rotation charge.

Or you could spend the $600 for the tool and do it yourself. This is a Federal required law as a result of all the suvs that have rolled over because people wont check their tire pressure.

Ducit Amour Hybridae
Mark Smith
Master Certifited Technician
Tempus non reparabilis fugit
"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it."

Best Tank 35.0 MPG

Have no problem with the sensors.... just feel that the system could have been designed better to recognize 5 tires, and always check it was geting a valid pressure from 4 of them.

Thanks for the replies. I have checked the other threads and as mentioned in your notes, I have had the dealer reset the sensors, but this has not solved the problem. Do I need to assume that they didn't actually reset them or that there is something wrong with the installation on my full size spare or one of the other tires?

The other thing that seems strange is that the alarm comes in on seemingly random times when driving, which makes me think that the problem is with one of the sensors or the way it was installed.

The randomness has to do with the system I think... they only transmit after fairly long periods, to make their internal batteries last. They also only transmit when they are rotating. So it appears random when the "timer" is up and the tire is rotating....

I don't think they set them right. Its a matter of "retraining" the system. Maybe they just reset the code in the OBD system and cleared it and did nothing to the TPS sensors because they didn't understand the request.

I'm just mad about the whole deal, I have to buy a $600 tool that just resets the TPMS system so I can rotate customers tires (some have specific loctions) and customers dont understand that it takes more time (money) and special tools (more money) so they are iritated that I charge more to rotate their tires.

Whats most likely happening is the spare tire is sending a signal that it is not turning and setting a fault code then turning the light on. You may have to remove the sensor in the spare as this system will not recognize 5 tires.

Ducit Amour Hybridae
Mark Smith
Master Certifited Technician
Tempus non reparabilis fugit
"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it."

Best Tank 35.0 MPG

It seems random but it probably isn't. The system only reads the tire pressure data when the vehicle has been moving at over 20mph for longer than 20min. That rarely happens in city driving, but you can test it by doing a 20min freeway run from stopped. My warning would come on in exactly 20min, as specified.

The stored code from the alarm is supposed to indicate which wheel position is reporting the fault. The dealer should be able to then tell you which wheel is reporting. If that wheel is your full size spare and the system was already retrained, then maybe the spare does have a problem.