'02 Q45 - tire pressure monitor reads "??" on all 4 tires

[Jerry in Bremerton]

On my 2002 Q45 Sport, I get no reading on my tire pressure for any tires. It just reads "??". It will do so even if I've driven 200 miles straight. This has never worked since I bought it last year.

Also, anytime I drive more than about 50-80 miles or so without stopping (which is rare that I go that far), I always get a "low tire pressure" screen message and the yellow light in the dash. After pulling off road and checking a few times, nothing is ever actually wrong.



Anything to reset or simply clean that may alleviate this? Thank you for any input.



On a side note, this was the only issue the person (private seller) I bought the car from a year ago said was wrong with it. Thankfully he wasn't lying. It's been a perfect car otherwise. (has 126k miles now, 10k since I got it) I was worried since it came cheap at 7k. He was just desperate to sell.

[djwarner]

First question: Does the tire pressure warning symbol on the instrument panel work correctly? On with the ignition switch on before engine start and stays off after start.

If so, there is a communication problem between computers. Check for blown fuses.

If not, the sensors in the wheels may have been damaged or changed and not registered. Registering must be done at a dealership.

[Jerry in Bremerton]

I just went out to car to verify that...

I think the trouble lights work properly, as you describe:

To clarify, when I turn ignition to "on", the ones that relate to the tires (Slip, ABS, pressure) stay on for about a second, as do the lights for AT check & VDC off, they stay on for about a second as well. The lights for check engine, oil, etc stay on when key is in that position (car not running). When I turn ignition and start the car, all the trouble lights turn off.

While driving, the SLIP light will come on momentarily when the tires aren't gripping, working as it should as far as I know.

When car is running, the tire pressure light in dash is not on. No trouble lights are on, all is well. The in dash tire pressure light only comes on after extended periods of driving. It comes on right when I receive the trouble message in the LCD screen and stays on until I shut the car off. It won't come on at all when I only drive say 20-40 miles or less, which is typical for me.

Sounds like I should check fuses.

[szh]

SWAG: Does the tire sensor need a battery or anything like that?

Z

[djwarner]

I just went out and doule checked mine. The low tire symbol looks like a cross section of a tire it is orange and is positioned to the right of the ABS symbol.

Yes it comes on for a second immediately after moving the switch from ACC to ON.

Some one here will point you to the service manual online (I downloaded it and can never remember where it is) . The system is in the WT section.

[DML]

YOU will probably need to have your tire sensor on the rimes cause every i switch rims on mine i get the same problems