Help requied in diagnosing PDC fault code

[Ronin]

I've had numerous issues with PDC in my A8.
I've replaced all front and all rear sensors, front ones still don't seem to work but they stopped throwing codes, i think maybe the speaker for the front ones may have gone?

With the rear ones I'm getting one code:

01549 Supply Voltage for Parking-Aid Sensor 29-00 Short To ground.

Could this be a wiring fault or maybe the PDC module in boot can be faulty?

[HPsauce]

This may help: http://wiki.ross-tech.com/wiki/index.php/01549

I don't know which measuring block to look at but you can usually cycle through them quite quickly.

[Ronin]

Originally Posted by HPsauce

This may help: http://wiki.ross-tech.com/wiki/index.php/01549

I don't know which measuring block to look at but you can usually cycle through them quite quickly.

Hmmm, ill be trying this next:

"One faulty sensor can cause this DTC and drop the Sensor Voltage Supply MVB reading. Unplugging the front -or- rear wiring harness to eliminate 4 sensors at a time is advised during the diagnosis. Make sure to cycle the ignition off and back on before evaluating the MVBs. After the front -or- rear of the vehicle are determined to be problematic it is recommended to unplug the senors one at a time to see which one crashes the Sensor Voltage Supply MVB reading."

thanks!

[HPsauce]

Logical, Captain.

[Ronin]

It's raining outside so I can't have a look at the moment but I've had another thought:

When I drive with the handbrake on, i get no beeps, just the light onthe dash show up, would the speaker responsibile for the hand brake beeping be the same as for the front sensors? I know there are 2 speakers 1 in rear for the rear and 1 in front for the front, if thats blown, it would be showing as short to ground and would explain the error.

[HPsauce]

Does the handbrake light trigger a beep, not on my car?

As far as I'm aware the handbrake warning light is a totally dumb circuit. I've even driven significant distances with it (partially) on...….

So IMHO the handbrake isn't going to help diagnose the fault.

I did look into the handbrake warning circuit ages ago when mine broke but don't recall the details of what I found. Replaced my mechanical switch with a magnetic reed switch as used in door sensors of domestic alarms.

[MikkiJayne]

Originally Posted by Ronin

Unplugging the front -or- rear wiring harness to eliminate 4 sensors at a time is advised during the diagnosis.

This means the plugs on the bumpers, not on the module itself. Both are on the left side clipped to the bumper bar, rear is above the tailpipe, front is under the headlight. Headlight lower trim off and bumper bolts out and you can pull the bumper forward enough to disconnect it.

[Ronin]

Ahhh so I've had it all wrong completley haha. thanks!

[Ronin]

OK, after unplugging the rear sensors it made no difference, when I unplugged the front,
01549 Supply Voltage for Parking-Aid Sensor 29-00 Short To ground error dissapeared, and I got 4 errors saying all 4 front parking sensors are missing.

I measured resistance on all sensors, it was all checking out fine at 10k ohm.

I had no idea what to do, so I took another good working sensor I had, and one by one swapped it with all the sensors in the front bumper, and boom. one of them was faulty even though resistance reading was ok.

1 faulty 12.99 sensor out of 9 i bought is better than 8 working 89.99 geniuine audi sensors any day!