Check your tire pressure!! This is the message that the Tire Pressure Monitor gives you when the circumference of one of your tires goes below what was calibrated. The Tire Pressure Monitor doesn't monitor actual tire pressure. It is calibrated while your car is running at a constant speed (~60 mph), and measures the "size" of the tire. When the size changes, that's the error you'll get.
odds are nearly 100% that you have one tire that's lost some notable pressure. it may NOT look like it - but test the pressures and that's most certainly what you'll find.
find the section in the manual on setting the tire pressure monitor. once you've gotten your pressures to where you want them (c.f. other postings for debate on this issue) follow the instructions to reset the tire pressure monitor.
anybody know the answer to this: why does the tire pressure monitor sometimes tell you that there's a tire pressure problem and sometimes it gives you the extreme TIRE DEFECT error? why the difference? this happened to me and my dealer couldn't explain.
'01 M Roadster (on order)
98.5 A4QS (it snows here)
[This message has been edited by SAB (edited 10 November 2000).]
There are older threads on this topic with more info. Several of us have had false "defect" messages when coming down from altitude. I doubt, however, that a bump would cause it unless we're talking about a pothole so severe that the bead actually separated from the rim and air was lost.
Yes, the system uses the wheel speed sensors, and looks for relative differences in speed between tires due to minute changes in circumfrence of the tire when pressure changes. This is why neither calibration or detection is instantaneous.
Procedure for "calibrating" the system to your tire pressure is in the owner's manual. The messages in the display are not clearly worded, but the procedure works. If you've done it properly, after driving SEVERAL MILES you will get comfirmation that the system has been calibrated.
Greg is right. The only way that a bump would affect the tire pressure monitor is that if the tire leaves the ground after it hits the bump or pothole. The wheel speed sensor could detect the slight change in rotation speed and report it as a tire pressure problem.
Pretty picky sensor system and it probably requires that you go through the whole calibration drill to reset it.