A6 Allroad - intermittent warning lights

[Lotobear]

Occasionally but now with increasing regularity I'm getting the full range of warning lights - tyre pressure, abs, parking brake, traction control and air suspension. This often happens where reversing oddly enough and can then just disappear as fast as it came. Car drives as normal.

I'm instinctively drawn to a wheel speed sensor, any other thoughts?

[Lotobear]

Still no further forward but pretty sure it’s not the battery. I’d say 80% of the time it’s triggered by low speed manoeuvres especially when reversing in full lock. It can resolve itself as suddenly as it comes. One odd effect is the sense that the engine is wanting to go when in drive with foot on the brakes waiting in traffic-seems to labour against the brake. Any thoughts welcome

[PushedDover]

I think I can offer my own experience in this - https://www.pistonheads.com/gassing/topic.asp?h=0&...

Faulty ABS Sensor / cables, can really FUBAR the brain.

[OldGermanHeaps]

What does a vcds scan say?

[Huzzah]

I had similar on a merc, full lock in reverse, bumps and bad weather seemed to be the trigger.

Traced it to the wiring for front wheel speed sensor.

[miniman]

Yes that set of faults was wheel speed sensor for me, that needed replacing and the loom re-pinning as initially the new sensor didn’t cure it. The car needs to know the wheel speed for all those systems to work.

As an aside, mine does seem prone to a lot of failed bulbs, parking sensors and general electrical gremlins like the infotainment rebooting randomly from time to time. I think I’m going to wind it in against something else.

[Dr G]

Just had an RS6 do this with very similar symptoms (was wheel speed sensor), albeit initially fooled by a worn-out main battery.

[Lotobear]

Thanks for comments - a scan showed a few fault codes but also front NS wheel speed sensor so I will do that first and see how it responds.

....I also have that shonky control box under the mid rear seat that occasionally throws a steering fault when the car is loaded with rear seats down so I will look into that as well.

[catso]

Lotobear said:

Still no further forward but pretty sure it s not the battery.

I had an A3, 3.2 DSG that had a bit of an appetite for batteries - got through 3 in the 12 years I had it.

If starting with a low charge in the battery, it would cycle all the warning lights.

Sometimes they would eventually go out and normal service be resumed but, on 3 occasions faults remained and the gearbox gradually stopped shifting into various gears until I was left stranded in neutral with no drive.

If I switched off and restarted it would generally be fine and a fully charged or new battery always solved the problem.

[Lotobear]

catso said:

Lotobear said:

Still no further forward but pretty sure it s not the battery.

I had an A3, 3.2 DSG that had a bit of an appetite for batteries - got through 3 in the 12 years I had it.

If starting with a low charge in the battery, it would cycle all the warning lights.

Sometimes they would eventually go out and normal service be resumed but, on 3 occasions faults remained and the gearbox gradually stopped shifting into various gears until I was left stranded in neutral with no drive.

If I switched off and restarted it would generally be fine and a fully charged or new battery always solved the problem.

I had the battery tested and it came out 'good' but I will not entirely discount it as another thing I've noticed is the effect appears to be more frequent in very cold weather.

...but with a new battery costing £230 I'm inclined to try other things first.

[Huzzah]

Lotobear said:

Thanks for comments - a scan showed a few fault codes but also front NS wheel speed sensor so I will do that first and see how it responds.

....I also have that shonky control box under the mid rear seat that occasionally throws a steering fault when the car is loaded with rear seats down so I will look into that as well.

Before replacing I'd try the following.

Jack it up, wheel off, ignition on. Full lock both sides and wiggle the wiring see if you can get it to trigger a fault.

[Lotobear]

Huzzah said:

Lotobear said:

Thanks for comments - a scan showed a few fault codes but also front NS wheel speed sensor so I will do that first and see how it responds.

....I also have that shonky control box under the mid rear seat that occasionally throws a steering fault when the car is loaded with rear seats down so I will look into that as well.

Before replacing I'd try the following.

Jack it up, wheel off, ignition on. Full lock both sides and wiggle the wiring see if you can get it to trigger a fault.

Thanks, that's a good suggestion!