ABS, ESP, Headlight Range, Parking brake warnings

[Marty87]

Hi there,
Thanks for taking the time to read this.

I have a 2008 Audi A5 3.0TDI. Recently i was away for two weeks and when i came back, the car battery was flat and car locked. The lock barrel was seized and couldn't get it open (a whole other story). A mechanic kindly helped me out. I started to charge the battery on the car, mechanic said it would be fine but when i heard humming, i removed the battery and charged it in the garage overnight. next day i re-installed the battery and went for a drive, no issues at this point. I parked up after 20mins and went into a shop. 20mins later i returned to the car switched on the ignition and began to reverse out of the parking space. At this point i got a 'headlight range defective' warning on the dash, followed by ABS, ESP and Parking brake malfunction warnings, all yellow. The parking brake works fine and the headlights seem okay too, hard to tell if ABS and ESP are okay. The warnings remain every time i start the car but the car runs fine. I took it to the mechanic for a diagnostic. I was hoping that after being in a low power state that i'd had intermittent failures and the whole thing just needed reset. However, the mechanic tried clearing the faults but they all came back on again almost straight away. There was also a fault code for rear left wheel speed sensor. The mechanic wasn't certain this would cure it so i asked him to leave it for now.

I read on a forum that it might be a relay or two under the ECO behind the wiper in the engine bay. Apparently water can get in there and damage things. However, i opened this compartment and it is bone dry throughout and so i didn't fancy taking anything further apart.

Can anyone offer any advice as to what might be wrong? I just can't think how a wheel speed sensor can cause the headlight range issue.

Thanks!
Marty

[philipharmes]

You will need the fault codes read with VCDS, some of the diagnostic readers used by general garages won't read all the fault codes.
Get the codes read & post them up.

The parking brake module is especially susceptible to low battery voltages.

I suspect your battery probably needs replacing.

Check the battery voltage after being parked up overnight & let us know.

[Crasher]

If the battery is the original, I would start with a new one.

[Marty87]

**FIXED**
Thanks for all your suggestions guys. New battery installed (was needed anyway) but all faults remained. A few weeks later, I replaced the ABS sensor and it cured ALL warning lights (ESP, ABS, Parking brake, Headlight Range).

Details about how I replaced the rear left ABS sensor (not saying this is the best or only way to do so.. For example, the ABS sensor can be checked without removal using a multimeter, but I decided against this after seeing the space constraints at the back of the sensor.)

Prep
Jacked up car, made safe on axle stand and removed wheel.

Removing old sensor
Located ABS sensor on rear of hub
Disconnected cable from ABS sensor and taped cable safely out of the way
Removed socket head screw fixing sensor using allen key
Tried to pull the sensor out of hole. it was stuck well and good and eventually snapped off, leaving half the sensor inside
Drilled a 2mm hole in the back of the stuck sensor, 5mm deep
Screwed wood screw into the hole until it had a good purchase on the sensor
Used a claw hammer to carefully lever out the remaining piece of the sensor

Cleaning the hole
Used cotton buds to remove crud, mud and a small fragment of metal from the sensor hole

Installing sensor
Pushed the sensor carefully home, aligned with the fixing screw
Re-fastened socket head fixing screw
Reattached sensor cable, ensuring connector clicked fully home.

Sensor was £19.

Thanks