Need wiring diagram to find where the OBD connects to

[adamc633]

Hello everyone, first thank you for your help. Ok now onto the problem. So I have been working on my 2001 S4 and I had an issue with the OBD port. Long story short, it's not functioning properly and need to find where its wires lead so I can clean connections, and rewire if need be so I can then scan my car. I need a wiring diagram with the obd port and where it leads. Or to know where it ends at so I can go there check the wires and connectors and do the repair and then scan my ecu and drive into other problems.

The obd does sometimes light up my OBD2 led and has stayed lit long enough for my program to register. But that's it so after many hours and head banging i have narrowed my problem to the OBD port and its connectors and its wires. So yeah help please and thank you.

[neilthewheel]

Should be able to find the wiring diag pdf for and a4/s4 from ELSA if you search around.

[adamc633]

That's my problem I have a lot of wiring diagrams and I am lost in them and cant really read them. If I could get someone to point to the starting location of the obd2 on one then I could go from there

[adamc633]

I got visual on the power one to pin 16. I just need to know where the rest of them go. I do not have a solid connection somewhere as the light on the scanner flikers

[ReggieNoble]

Not sure if this is 100% correct, but it's what I found with a quick search.Screenshot_2019-09-14-17-31-53.jpegScreenshot_2019-09-14-17-33-18.jpeg

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[Mille Bornes]

I had a tt with no com. One of the modules was bad, sending 12v onto a data line. So it's possible you've just got a faulty module somewhere

[adamc633]

Thank you, I am aware of it. Now here is the hang up. I connect my scanner obd2 to the obd port and the light on the scanner lights up for a little and then flickers and then turns off. I have disconnected the radio. So something on the lines is causing the problem. The power line is good. I get 12v and the fuse is good. So what moduals am I looking for and also. I am trying to find the routs of k-line wire and the others. I really do appreciate your help guys. This has been a huge hurdle that has stopped me from being able to fix everything else wrong.

[neilthewheel]

Flickers and shuts off sounds like the scanner or the 12v or gnd in the connector.
If it was one of the other wires Id think it would just lose connection or not communicate.

Post some decent screen shots of the diag you have and Ill take a look.
The tracked style diags are a lil strange at 1st, but really nice once you get your head around them.
The ones that show everything were nice when stuff was simple, but nowadays that style is right up there with trying to follow some crazy trace on a circuit board.

[adamc633]

I have a obd2 scanner to USB and it works fine in my friends audi.

[adamc633]

So my scanner tool is fine. So what do I need to be looking at. Where do the grounds go to? I have been trying to find a wiring diagram and have had no luck.

[Protection]

So my scanner tool is fine. So what do I need to be looking at. Where do the grounds go to? I have been trying to find a wiring diagram and have had no luck.

The proper way to diagnose this is with an OBD breakout box and a lab scope. That way you could check the signal on the CAN lines while you do the “unplug it” test and see if the signals return to normal when you hit the malfunctioning module.

But...in the absence of those tools, first check all your grounds, including the ground from the right side of the engine block to the frame rail. A bad ground will cause non-com with OBD port. Next I would unplug the ABS module and see if communication is restored. One of the terminating resistors (there are two 120 ohm resistors in the CAN line) is located in the ABS module. From there, I would just start unplugging modules in the CAN line until communications is restored. I don’t have a wiring diagram handy, but if I have a chance I will look up all the modules on the CAN line and their location.

Also, you should not being seeing any more than the 5v on pin 6 of the OBDII connector. More than 5v is indicative of a failed module.


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[mikeb17]

Maybe one of these may help. If not then maybe they may help someone else who searches wiring diagrams


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[mikeb17]

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[Protection]

Mikeb17, for me at least, those diagrams are so much more intuitive than the Audi/VW ones. Are those from Mitchell?


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[Weve1052]

New to the forums, not sure if this is where my issue belongs, got my b5 A4 about 2 weeks ago. Cel was on and found the OBD2 port had been cut off. Wires are there. Just no port. Anyone have a color Code diagram or could take a pic of theirs for a reference? Already have a replacement port it’s just not color coded. Thanks in advance for any input

[ReggieNoble]

New to the forums, not sure if this is where my issue belongs, got my b5 A4 about 2 weeks ago. Cel was on and found the OBD2 port had been cut off. Wires are there. Just no port. Anyone have a color Code diagram or could take a pic of theirs for a reference? Already have a replacement port it’s just not color coded. Thanks in advance for any input

This may help..20210215_125859.jpg
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