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Author Topic: B5 S4 - Could a bad AIRBAG module keep me from connecting to the ECU?  (Read 17754 times)
GWerks
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Hey guys,

Trying to help a friend out, he bought an s4 a while back and it came with an aftermarket stereo and a not working climate control module. Since he bought the car the AIRBAG and CEL have been on.

We knew that in order to be able to read the code he had to get rid of the radio and replace with a OEM one and get a new climate control, well, he did and he still can't connect to the ECU to check for codes.

We have done the following:

- Checked all the fuses
- Checked the fuse behind the radio (stock radio works fine now)
- Replaced the climate control (it works)
- Disconnected the ABS module
- Pulled the cluster fuse
- Disconnected the battery for a few mins
- Disconnected the radio
- Swapped ECU's
- Checked all the connectors in the ECU box

I'm out of ideas and any input would be awesome. I guess the only thing I can do is disconnect the AIRBAG module and see if that does it but is the AIRBAG module part of the K-Line circuit?

Thanks in advance,
GWerks
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ddillenger
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« Reply #1 on: January 13, 2013, 12:22:29 PM »

Why not run a seperate k-line right to the ecu? That would bypass any potential issues.
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GWerks
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« Reply #2 on: January 13, 2013, 12:27:18 PM »

I could do that, but I really just want to fix the problem.
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ddillenger
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« Reply #3 on: January 13, 2013, 12:41:27 PM »

You can't connect to ANY module in the car, or just the ecu?
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GWerks
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« Reply #4 on: January 13, 2013, 01:13:16 PM »

Any, I have tried with VAG COM, ECUx and Nefmoto and I just can't connect. I just disconnected the AIRBAG module also and nothing.
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corradovolksb
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« Reply #5 on: January 13, 2013, 01:47:18 PM »

The probmel is more than likely due to the aftermarket radio harness adapter to the factory harness a lot of the times when installing an aftermarket radio the Kline will get direct power because the installer will not know and connect the Kline wire to B+ causing no communication to the ECM. Try disconnecting the radio harness from the factory harness and see if you can connect.  If you can then just remove the kwire from the harness and you will be all set. The wire color should be gray with white tracer or gray with purple tracer.
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2000 Nogaro blue S4 Stage 2. VAG for life.
GWerks
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« Reply #6 on: January 13, 2013, 02:54:34 PM »

The probmel is more than likely due to the aftermarket radio harness adapter to the factory harness a lot of the times when installing an aftermarket radio the Kline will get direct power because the installer will not know and connect the Kline wire to B+ causing no communication to the ECM. Try disconnecting the radio harness from the factory harness and see if you can connect.  If you can then just remove the kwire from the harness and you will be all set. The wire color should be gray with white tracer or gray with purple tracer.

The car had a aftermarket radio but was replaced with the factory one.

As of right now, I have disconnected:

- ABS module
- Cluster
- Radio
- Airbag module
- Climate control

I still cannot connect to the engine module with VCDS, or just connect with ECUx or Nefmoto
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GWerks
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« Reply #7 on: January 13, 2013, 03:10:24 PM »

When I pulled the radio, I noticed there is a wire that goes from the black connector (brown wire) to an Audi connector, and from there it turns into a purple wire that goes to the red connector (see pic), my question is, the audi connector in between the black and red connectors is made for 2 wires but it's only carrying one, could this be my issue? Am I missing a wire?

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cerips
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« Reply #8 on: January 13, 2013, 03:13:23 PM »

The OEM head units normally have the wiring diagram on the back of them.
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corradovolksb
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« Reply #9 on: January 13, 2013, 04:22:07 PM »

Oh I misread thought you still had the aftermarket radio hooked up. Not sure what's up with the purple wire. Yes most factory radios have the wiring diagram on one side of the case. Sorry I can be of more help.
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2000 Nogaro blue S4 Stage 2. VAG for life.
corradovolksb
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« Reply #10 on: January 13, 2013, 04:32:04 PM »

This might be a dumb question but have you tried using a differant cable?
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GWerks
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« Reply #11 on: January 13, 2013, 06:40:12 PM »

Checked the radio on my buddy's AVANT and the connector only carries one wire =/

I have checked with 4 different cables and 2 different computers.... halppppp
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cerips
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« Reply #12 on: January 14, 2013, 10:32:14 AM »

Post a photo of the wiring diagram on the back of the radio so we can see what connector you're on about.
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GWerks
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« Reply #13 on: January 15, 2013, 07:41:20 PM »

Will post a pic of the diagram in the back of the radio tomorrow.

Update:

Hey guys,

As some of you know, I have been trying to track a short or a bad module that's stopping me from being able to connect to any module of the car (ABS, AIRBAG, ECU..etc) through the OBD2 port on my buddy's car.

- Old thread : http://www.audizine.com/forum/showthread.php/521336-Could-a-bad-AIRBAG-module-keep-me-from-connecting-to-the-ECU-or-any-other-module

I have disconnected every module that could stop me from doing this and I think there is a short of some kind on the radio wiring harness since it has been modified to fit an aftermarket radio, here are the pics of what I found after I did some ''digging'', hopefully somebody will be able to tell me if one of the wires that have been cut are K-line related.








Pics show a purple, grey and brown wires that look like they were just cut. There is also a black wire that goes nowhere but it doesn't seem like that one has actual wire inside of it. If anyone could tell what these 3 wires go to that would be awesome because I honestly don't know what else to check.

Thanks in advance,
GWerks
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corradovolksb
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« Reply #14 on: January 16, 2013, 11:38:17 AM »

I attached the radio wiring diagram. It looks like there isnt a K wire that goes to the radio. In the pictures it looks like you have canbus wires (the orange with brown tracer and orange with purple tracer) that go to the black connector so that means that your radio is prob not the cause of your issue and it could be a problem with your instrument cluster because the gateway moudule is in the cluster and allows canbus communitcation to all of the modules. I have had some cars that the cluster will not allow communication and after unpluging it and pluging it back in everything comes back online but you said you have already reset the cluster and it still does not work. I have had abs modules cause the canbus to go down also but you also said that you have tried leaving it unplug and still cant communicate so that pretty much rules that out. have you tried just unpluging the abs moudle by itself and leave everything else pluged in?
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2000 Nogaro blue S4 Stage 2. VAG for life.
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