This is a brand new car. Bought it last Saturday. Before we headed home, the Tire Pressure warning light came on. The salesman took it to the shop “to re-set”.

Later that evening the light came on again, when we started driving. The pressure was 38psi in all 4 tires, on the dot. I then learned how to store tire pressure in memory as a baseline, and the light went off.

And then it came on again and I was told to check the spare. It was low, I brought it up to 38-40psi, re-stored the new baseline pressure in memory.

The light is back on. I will stop by at the dealer’s tomorrow morning. I will appreciate it if someone gives me a crush course (or points to a web site if there is one) on the technical side of the problem. Logically, it’s either a faulty sensor or a “controller”, if there is one, or both. I also assume that a dealer’s service techs must have enough equipment and brain power to properly diagnose a problem at once. May be I am wrong on all points but I have to be prepared by 7am tomorrow.

TIA,
Boris

 

Try posting this in the B7 section of the A4 forum to see if someone else can help you out.

 

Before you read on: if the spare is full-sized, take it out of the vehicle if it has a sensor installed. If the light goes away, you know the control unit is confused due to the spare. I have not worked on a car yet that has a monitored spare (but there's always a first).

TPMS in a nutshell:

There are antennas, triggers, a sensor in each wheel, and a control unit. A trigger tells the pressure sensor in the wheel to read the tire pressure. The signal is sent via radio waves back to an antenna, which sends the reading to the TPM control unit. There's a little more to it, but that's the gist.

If you are getting a "flat-tire" warning and the tire pressures are in fact correct, you liekey have a sensor issue in that wheel. If you are getting a "low pressure" warning, the sensors may simply need to be learned.

To get the TPM control unit to learn the wheel sensors without a VAGcom, set the dash to the correct wheel and tire package installed (summer, winter, 17", 18"...). Set the tire pressures 2 psi above the required pressure (use a digital gauge). Get in and drive down the highway for 20 minutes consecutively. The TPM control unit -should- learn the sensors and the light -should- go off.

If the warning is still on after about 30-40 minutes of driving, the codes in the TPM control unit will need to be read.

P.S.: TPMS can be a real headache to diagnose. If they need some time to get it right, don't be surprised. I've had to rework entire antennas and TPMS harnesses on more than one car to get the system to read correctly. I'm not trying to scare you, just saying it's far from perfect and for some reason, radio interference is a larger problem for some. If it's brand new, I'm betting on the sensors not being learned yet.

 

Thank you kindly, Tweaked. I understand the tech. side of it. I may have to become an expert in setting up this system. It's unlikely the dealer's techies will fix in in an hour.

 

Not a problem. Did you try driving it first?

 

Not a chance in hell LOL.

 

TPMS = worst POS evar when it breaks

 

Thank you all who responded. This was a nasty problem to fix, took the dealer all day, but my wife is happy. Here is the summary from the ticket:

“Tech found Fr Left sensor malfunctioning intermittently. Tech used TPMS diagnostic tool and found all sensors working 12 times. Tech found once 1 sensor failed after test drive. Tech has swapped TPMS modules with known good one. Tech swapped each wheel with spare and test drove to isolate faulty component.”

Hopefully, it will help someone else.

 

Cool. It could have been a much larger headache. A faulty sensor is not so bad. Glad it worked out for you!