Hi Guys! First post here! I was directed over to this forum by someone on another Audi forum. I did search here for the answer to my question, but I could find what I'm looking for. I'm hoping you can help me here. I'm pulling my hair out trying to find the correct wire(s) for the MIL/CEL (K83) for my '98 Audi AEB conversion and it's making me feel like an idiot. I have been through every thread that could find, every FAQ that I could find and all through the Bentley and I still haven't come up with an answer.

The crux of the question is which wire(s) coming out of the ECM on a 1998 A4 AEB are correct for making the MIL/CEL work?

I looked through the Bentley wiring schematics looking for the 1998 AEB MIL lamp wiring, and this what I have found:

The 1997 schematic shows the MIL (K83) wiring coming from pin #17 on ECM. This wire is a ground wire to activate the MIL lamp.

The 1998 AEB schematic shows ECM Pin #17 as the Trailer Operation Indicator Light (K18) which appears to be a power wire to activate the lamp (obviously this has nothing to do with the 1998 MIL, but I simply made the connection to show that the 1997 ECM wiring appears to be very different than the 1998/early 1999 wiring).

I could not find a MIL (K83) wire in the 1998 schematic at all. The early 1999 schematic is the same as the 1998.

The late 1999 schematic has a K149 lamp labeled a "Warning Light for Motor Electronic" (I don't know what that is exactly). However, this wiring track goes nowhere. It does connect to connector T32/13, but that's as far as the information leads. Pin #17 on the late 1999 ECM also goes to the Trailer Operation Indicator Light (K18), so it appears similar to the 1998 wiring.

For 2000, the schematic shows the MIL (K83) lamp as ground activated from ECM pin #47. This appears to be a similar layout as the late 1999 described above. The MIL (K83) lamp is shown to be connected via T32a/14 (which happens to be the Fault Light for Power Accelerator Activation lamp connection in the 1999 Schematic). Pin #17, which is used for the Trailer Operation Indicator Light mentioned above, does not appear to be in use with the 2000 wiring, indicating that the 2000 wiring is very different than the others.


(Just to be clear, I only mention the ECM Pin#17 and the Trailer Operation Indicator Light as a comparison between the 1997 ECM wiring (which shows ECM pin #17 as the MIL K83) and the other years)


So what happened in 1998 and 1999? Does the ECM in those years follow the 1997 (it appears not, but...) or 2000 format or neither? I'm really at a loss here, so if anyone can help me figure what wire is associated with the MIL/CEL (K83), I would REALLY appreciate it.

 

Man, I really hate bumpin' my own thread, but I have exhausted all of the avenues that I can think of and I'm hoping that someone who knows will see this and be able to help.

 

Audi had different instrument clusters, ECU part numbers, etc. in 1997, 1998-1999, 2000, 2001 (clusters in 2000-2001 were the same). Perhaps you may wish to try figuring out this problem in reverse; see which wire on the cluster side is the one used to trigger the CEL. I don't have my Bentley handy, but in this thread under "cluster 2" (I think that's what you should have) pin 16 on the 32-pin Blue connector going into the instrument cluster appears to be the trigger wire for the CEL. In your Bentley it should tell you where the other end of that wire will go to, so should pinpoint a wire on the ECU wiring harness. If it points elsewhere then you'll know where to shift your investigation.

 

MetalMan, thank you for the link to that thread. I do indeed have "cluster 2". This puts me a little closer to the answer, but I'm still coming up a little short.

Pin #16 on the 32 pin blue connector on cluster 2 is labeled as the "Trailer Operation Indicator Light" in the Bentley. This wire can be traced back to pin #17 on the ECM, again in the Bentley. The cluster of lights that include the Trailer operation Indicator Light in the instrument cluster appear to share a common ground - pin #24 on the 32 pin blue connector.

HOWEVER...I'm having a hard time trusting the Bentley manual at this point. Assuming the manual is correct, pin #17 coming from the ECM should be a power wire to activate the CEL. I tried to jump the pins with power and ground in an effort to activate the light in the instrument cluster, but that didn't work. I tried many different combinations of things to try to get the lamp to light up, but nothing. I did check the bulb and it's good. I even tried tracing the track through the instrument circuit board, but can't seem to keep track of where it goes. My attempts to try to activate the CEL via jumping the wires at the pins in the connector has yielded zero results.

I still feel pretty lost here. I don't have the engine up and running yet, but I may have to wait until that happens to help determine the correct wiring.

Thanks again for the help.

 

This weekend I plan to do some instrument cluster work. One of the things I will attempt is add a wire from the fuel consumption signal on the ECU side to the red 20-pin connector on the cluster side.

But my point is, I can check to see if I get continuity between ECU pin 17 and cluster pin 16 - sounds like in theory this is the wiring that would enable the CEL operation based on what you've listed. And since I have a 1998.5 1.8T (cluster 2, AEB) the wiring should be similar to what you're working with... right?

 

Oh man, if you could do this for me, that would be great!!! I would appreciate that to no end!

Via PM, I spoke to audifirst, who is the author of that excellent list of clusters and pins in the link you directed me to, and he confirmed that pin #16 on the cluster 2 is definitely the feed to the CEL. So yes, if there is continuity between ECU pin #17 and cluster pin #16 (at the blue connector), then we will have found the correct wire.

Good luck with your other ECU/cluster project as well.

 

Turned out that this exercise was useful for the work I'm doing for my cluster conversion (figuring out the ECU pins and whatnot).

I have just confirmed that pin 16 on the blue instrument cluster connector (T32) has continuity with ECU pin 17 (on the longer connector). The wires are also both the same color: yellow/brown.

 

YES!!!!!!!


Thank you SO much for doing that! Since my wiring harness is not complete, it would have been impossible for me to test that. I really appreciate it!

 

No problem In theory I could have taken it one step further and unplugged pin 16 from the blue cluster connector to test CEL functionality, but at the time I still had the ECU unplugged (no ECU = no CEL).

Interestingly enough, the Fuel Consumption signal from the ECU that I was looking for is pin 18... right next to the CEL pin

 

I know it's a little late to help. But for anyone needing to know in the future, you can find the pin outs for B5 clusters here.