'99 Audi A3 - ABS error codes

franksm

Hi folks

Looking at a friend's Audi A3 ('99 with AHU 1.9TDI engine) via a VAG U281 scanner, as the ABS warning light is all lit up. Error codes as follows:

18256 <?>
00283 <ABS wheel speed signal 1, left front>
00283 <ABS wheel speed signal 1, left front>
00290 <ABS wheel speed signal 3, right rear>
00290 <ABS wheel speed signal 3, right rear>

What is 18256 ? It's not listed in the scanner's index. Seems odd for two sensors to be problematic all of a sudden, especially on diagonally opposite corners.

I plan to pop the ABS ECU out and ensure the contacts are clean, and to pop the wheel sensors off the hubs and clean them (it solved an error on my Merc a while back, the sensors were covered in muck and metal filings). Will also change the brake fluid as... well, why not, it's an easy job.

The car has been fine up to this point, but was in a minor accident (truck turned over the front bumper and wing of the car, cosmetic damage only) which was repaired and 'something' done on the brakes at the same time (I am assuming it was the pads being changed, but there's no detail forthcoming from the owner :pac:).

Any ideas welcome

Frank

jawnuolis

franksm wrote: »

Hi folks

Looking at a friend's Audi A3 ('99 with AHU 1.9TDI engine) via a VAG U281 scanner, as the ABS warning light is all lit up. Error codes as follows:

18256 <?>
00283 <ABS wheel speed signal 1, left front>
00283 <ABS wheel speed signal 1, left front>
00290 <ABS wheel speed signal 3, right rear>
00290 <ABS wheel speed signal 3, right rear>

What is 18256 ? It's not listed in the scanner's index. Seems odd for two sensors to be problematic all of a sudden, especially on diagonally opposite corners.

I plan to pop the ABS ECU out and ensure the contacts are clean, and to pop the wheel sensors off the hubs and clean them (it solved an error on my Merc a while back, the sensors were covered in muck and metal filings). Will also change the brake fluid as... well, why not, it's an easy job.

The car has been fine up to this point, but was in a minor accident (truck turned over the front bumper and wing of the car, cosmetic damage only) which was repaired and 'something' done on the brakes at the same time (I am assuming it was the pads being changed, but there's no detail forthcoming from the owner :pac:).

Any ideas welcome

Frank

18256 engine control module (ECM) probbable couse trouble code(s) stored

crosstownk

I'd go with cleaning the sensors and trigger wheel first. Also, have new tyres been fitted recently? Are the tyre pressures correct. Rotational differences between wheels can trigger an ABS fault. I've often come across incorrect tyres & pressures that cause sensor faults.

Will these faults erase? Are they permanent or sporadic?

crosstownk

jawnuolis wrote: »

18256 engine control module (ECM) probbable couse trouble code(s) stored

Correct - but I thought that a 1999 A3 had a seperate ABS ECU? (I could be wrong). However, I'm sure the ABS shares it's information with other systems via the CAN gateway.

franksm

Thanks lads

They do erase, but 18256 comes back straightaway and is being listed as an ABS trouble code rather than an Engine code. I haven't driven the car since erasing them (car is blocked in driveway), so i bet that's why the wheel sensor errors aren't reappearing.

The tyres are cheap and nasty, and they do look as if they are needing pumped up. Would mismatched air pressure be enough to annoy the ABS ECU ?

crosstownk

franksm wrote: »

Would mismatched air pressure be enough to annoy the ABS ECU ?

Yes but it would take quite a few PSI in the difference to alter the rolling circumference out of tolerance to the extent that a fault is recognised - but I have seen it happen.

Mr.Diagnostic

Your 18256 is just telling you to check the error memory of the engine module. So thats what you need to do

franksm

hey dudes

right rear tyre was down to 15psi, plus I cleaned the ABS sensor. The error has gone away.

Front-left ABS sensor was covered in rust dust from the disc, so cleaning that seems to have solved the problem.

Engine ECU is giving an error 550 "Injection Start Control" - although the check-engine lamp is not lit, so I guess the car isn't in 'limp home' mode. Seems to be going rather well. Wonder what that error refers to ?