NefMoto

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

Why not run a seperate k-line right to the ecu? That would bypass any potential issues.

I could do that, but I really just want to fix the problem.

You can't connect to ANY module in the car, or just the ecu?

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.

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

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?

(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo-2-1_zps9dea5f62.jpg)

The OEM head units normally have the wiring diagram on the back of them.

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.

This might be a dumb question but have you tried using a differant cable?

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

Post a photo of the wiring diagram on the back of the radio so we can see what connector you're on about.

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 (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.

(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo1-1_zps3587fb3b.jpg)
(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo5_zps8a5d7448.jpg)
(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo4_zps2f4455b7.jpg)
(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo3-1_zps1c6b6c55.jpg)
(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo2-1_zps75c3257d.jpg)
(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo1-1_zps81e09396.jpg)

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

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?

Thanks for the diagram, I was about to post it.

As of right now, I have the cluster disconnected, ABS module, radio, climate control, and AIR BAG module. It's weird because when I try to connect to ENGINE with VCDS, it takes about 15 seconds for the warning to come up, almost like if I had just turned on the key when I clicked on Engine.

The K line wire to the radio is green/blue.

(http://i1281.photobucket.com/albums/a502/GWerksTuning/photo-1-1_zpsa7b759ec.jpg)

Ive had a radio problem pull down all communications before.

Figure out that radio wiring I bet that is your culprit.

I have checked the K line and CAN wires on the radio harness and they look intact. I'm going to see if I could have a bad OBD2 port, I will be testing the voltage between pins 7 (K-line) and 4 (ground), I guess I will find out then.

Things I have done:

Disconnect ABS module (remains disconnected)
Disconnect AIRBAG module (remains disconnected)
Disconnect cluster
Disconnect radio (remains disconnected)
Disconnect climate control unit (remains disconnected)
Disconnect central locking pump (remains disconnected)
Disconnect headlight leveling module (remains disconnected)
Disconnect ultra sound sensor module (remains disconnected)

So every module K-line related has been disconnected, going to see if the K line wire has power, if it does, then I will know it's a bad obd2 port or something else.

The multimeter read -040 - -043 ohms between K line wire at the OBD2 port and ground. Does this mean it's working?

I had a similar problem with my buddy's 2000 s4, it would only connect to the ECU if the car was running.  After he replaced his ABS module for some reason these problems have gone away? 

your last post you said you where checking for voltage at pins 7 and 4, why where you checking ohms? if you check for ohms with power to k line you can destroy your multi-meter ohms is for resistance with no power

What?

Ohms is used to determine the resistance of a wire, between two points.  The amount of current flowing through that wire is irrelevant to the multi-meter.

Only thing I can think of is that you mean measuring current, but instead of checking current flow, you short it out, to measure that max current that the circuit can supply.  If this max current is more than your multi-meter can handle, then, yes, it could break it.  Pretty sure that's why they invented fuses though.

Still not sure what you mean at all though.. haha

I would run a fresh line to the ECU, bypassing EVERY other k-line.

clearly you dont know what you are talking about! a ohm meter is used to test resistance  (no shit), when a ohm meter is used it puts out its own small electrical charge to test power should be removed, (if kline has 12 volts due to a misswire from a radio install and you check from kline to ground your running a charge threw the meter if YOU know it or not, that can short out the meter) i was mostly questioning why he checked for ohms when he said he was going to check for voltage
smart ass

"Remember!
You can only test resistance when the device you're testing is not powered. Resistance testing works by poking a little voltage into the circuit and seeing how much current flows, its perfectly safe for any component but if its powered there is already voltage in the circuit, and you will get incorrect readings
You can only test a resistor before it has been soldered/inserted into a circuit. If you measure it in the circuit you will also be measuring everything connected to it. In some instances this is OK but I would say that in the vast majority it is not. If you try, you will get incorrect readings and that's worse than no reading at all."

http://learn.adafruit.com/multimeters/resistance quoted

Incorrect readings, yes.  But you won't break it.

wrong again sorry

"An ohmmeter is a device that measures resistance. It is connected in parallel across the
resistance to measured. You should NOT measure the resistance of a resistor that is still
part of a circuit. You will probably destroy the ohm-meter, certainly you will measure the
wrong resistance. In practice first disconnect all leads of the resistor to be measured, so
no electric current runs through the resistor, except for the current supplied by the battery
inside the ohm-meter itself."

quoted  http://www.physics.rutgers.edu/ugrad/161/LabwmcorManualsPDF/ResistanceOhmsLaw/wm8corResistanceOhmsLaw.pdf

for real?