Tire Pressure Monitor Intermittent Failure

2007 530XI Touring Wagon, my TPM suddenly comes on while driving without any loss of pressure or flat tires. It resets OK. It has happened twice in the last month. Any ideas on how to check/fix?

Do you keep your car in a garage overnight?

It might be something as simple as reduced outdoor temperature causing a drop in tire pressure. Considering your location (Ontario), marked drops in ambient temps in the Autumn might be the cause.

More info: http://www.tirerack.com/tires/tirete....jsp?techid=73

HTH,
Jim / crewzer

The car is garaged every night. The tire pressures are all good, within 0.5 pounds on each axle.

Originally Posted by guydutil

The car is garaged every night. The tire pressures are all good, within 0.5 pounds on each axle.

Right but what happens is that as you drive outside where it is cooler, the tire pressure drops due to the drop in ambient pressue which kicks off your TPM warning. Nothing unusual for this time of year.

Right but what happens is that as you drive outside where it is cooler, the tire pressure drops due to the drop in ambient pressue which kicks off your TPM warning. Nothing unusual for this time of year

Almost! The tire pressure drops as a result of ambient air temperature being lower than garage air temperature. It's that dang Ideal Gas Law thing.

The car is garaged every night.

The solution is to normalize tire air pressure for outdoor conditions. The "old" way as to add ~1 lb of pressure for every ~10 degree F (~5 C) increase in garage temp vs. outdoor temp. This way, the tire pressure would drop to "normal" after the vehicle was moved out from the garage.

But, the TPMS may not be so easily fooled. I suggest you leave/move the car outdoors for several hours in the AM, set and check the tire pressures (different front & back?), and then reset the TPMS. This way, the cold tire pressure(s) and the TPMS will be set for ambient driving conditions instead of the warm and cozy garage.

Regards,
Jim / crewzer

Thank you All.

Crewdzer - I meant temperatuer - good catch and yes dang ideal gas law: PV = nRT - I was having flash backs to highschool chemistry and Chem 101 when I was typing up my response

Originally Posted by guydutil

2007 530XI Touring Wagon, my TPM suddenly comes on while driving without any loss of pressure or flat tires. It resets OK. It has happened twice in the last month. Any ideas on how to check/fix?

Are you getting a low pressure warning, or "TPM Malfunction" message? If the latter, then you may have a sensor starting to fail in one of your wheels - I had this off and on for a few months with my winter wheels until the faulty sensor was replaced.

I am getting "tire loss of pressure" quickly followed by "flat tire" warning. I will have my sensors checked.

Originally Posted by guydutil

I am getting "tire loss of pressure" quickly followed by "flat tire" warning.

I got the same message and warning this past Saturday. I had some wheel and tire work done that morning, and the techs didn't restore all tire pressures to the original references (30 F / 38 R). All is fine since I corrected the tire pressures and re-initialized the system.

HTH,
Jim / crewzer

Update?

Thx,
Jim / crewzer

I have increased all my tire pressures by 2 pounds. It seemed to have solved it for now.

OK; thx.

Regards,
Jim / crewzer