A3 8P Relief relay X-contact problem...

Hi!

"I bought a used A3 8P 2.0 TDI with a BKD engine two weeks ago, and I'm increasingly realizing that I've bought a real lemon... As it looks right now, the A3 has the well-known cylinder head problem with coolant loss in the first cylinder." Furthermore, I'm also experiencing several electronic issues...

"The X-contact isn't working; for example, the xenon headlights start flickering when the car is started, and the radio also stays on. How does this work in the 8P model? According to the wiring diagram, there's no more traditional X-relay (only for the climate control unit, as far as I can see). Does this all run via CAN now? Also, my LWRA (likely a module abbreviation) isn't accessible via OBD, and the instrument cluster is also showing errors. My PDC (Parking Distance Control) is showing an error that it's missing power supply to terminal 15, even though the control unit is only supposed to be powered by terminal 30 according to the wiring diagram." Just to add, the previous owner installed some kind of "device" in the trunk, and in the process, the original BOSE system was removed somewhat "unprofessionally" (although there are no exposed wires touching each other), and the original Chorus radio was replaced with an RNS-E, which has approximately 5 adapters behind the glove compartment.

Okay... Can anyone give me a tip right now??? I'm not really sure where to start looking... I would love to give that seller a good kick in the rear for selling me such junk.


greetings

X-Contact = Terminal 75. The relay is located on the vehicle's body control module (BCM), in the lower right corner. It is also appropriately labeled.

The fact that the xenon headlights remain on at startup is also the case with my 2008 Passat, and it's apparently normal. If they turn off, it's likely that the voltage is too low, indicating a weak battery or wiring with excessive resistance.

The radio (or RNS MFD DVD2) also continues to work without any problems when the engine starts.

Regarding the ALWR diagnosis: Which VAG-COM / VCDS version and which adapter are you using? The diagnosis for some control units may only be possible via CAN bus on your vehicle. Your diagnostic adapter needs to support that, otherwise it won't work.

If I remember correctly, components like the fans and windshield wipers are connected to the X-connector.

Regards,
Guste.

Hi!

Thanks for the tips... That's definitely a good starting point! So far, I've only experienced issues where the headlights, radio, etc., suddenly turn off. I've already located the relay on the body control module, but I was missing the wiring diagram showing how the radio and headlights, etc., are connected. In my case, the battery voltage definitely dropped, and I'm also dealing with the classic BKD engine problem, which tends to flood, making it difficult to start, and likely had excessive compression due to the water. He's already partially disassembled; I need to find a new head first.

He was diagnosed using a VAG tester, specifically a 5052B with a diagnostic adapter, so it should definitely be able to communicate with it... Does the A3 automatically lower and then raise its headlights when they are first turned on, using the automatic leveling system (AHS)? It doesn't work for me.

"Does anyone have any ideas on how the PDC control unit receives the signal for terminal 15, or what the problem is with my control unit, considering that, according to the wiring diagram, it shouldn't be receiving that signal at all?"

greetings

littleitus wrote:

Does anyone have an idea how the PDC control unit receives the signal for terminal 15, or what the problem with my control unit is, since according to the wiring diagram, it shouldn't be receiving that signal at all...?

Then you're using the wrong SLP!

Terminal 15 is connected via fuse SC8, 10A, via black/blue wire to the brown 16-pin connector of the PCD, pin 1. The constant positive voltage (KL 30) is connected to pin 3.

The diagnosis is performed via CAN bus, to the gateway control unit.

I cannot answer whether the xenon headlights on your car should be tilting up and down.

Regards,
Guste.

Thanks for the tips about the SLP! In the fuse box, the distribution cable for a "fuse row" wasn't properly locked in... And in that row, there were "only" 2 fuses... my PDC and the windshield wiper system! It's working again now...

I'm slowly starting to get a handle on all the problems with my "amazing" new used car...

Thanks.