K1 Short to +12 Factory Radio

DDanielson · Jun 9, 2018

I’m a new user and have a 2001 VW Cabrio GLX. The connection says “Questionable” and shows a K1 short to +12v. I’m the second owner and the radio is factory. I pulled the K1 line from the harness and taped it off but get the same error with the radio installed.

What else could be causing a K1 short to +12v? If I simply unplug the factory radio is that a likely fix for the issue?

iichel · Jun 9, 2018

short somewhere else in the wiring loom

DDanielson · Jun 9, 2018

The ABS light has been coming on intermittently. Also, I just completed the dreaded hot/cold blend door repair. Prior to that I had no CEL’s. I had to remove the dash and instrument cluster. I meticulously marked everything and took photos/notes. All the accessories work as they should but the immobilizer is engaged now. The engine will start and run for less than two seconds and then the engine shuts off. That’s why I bought the cable.

Any ideas on where to start? I have the Bentley manual with the wiring diagram. I’m a musician and own a company where I manufacture guitar effects pedals and design circuit boards so I’m pretty handy with that sort of thing. Thanks!

iichel · Jun 9, 2018

I'm not sure where to start, I don't know this kind of car so it's not possible to point you in the direction of the typical suspects.
What I'd do is just start systematically pulling fuses and see where it ends.
Pull a fuse (or on groups), clear DTCs, scan, see what happens.
This way you could try to isolate it to a module or a wire and from there, narrow it further down.

DDanielson · Jun 9, 2018

That sounds like a plan. I’ll have to pull fuses until the +12 on K1 goes away. I haven’t gotten far enough in the process yet to even register the vin with Ross-Tech, much less scan the vehicle. It might be easier just to push it off a cliff but I kind of love it. It’s been a relatively trouble free car up to this point.

Uwe · Jun 9, 2018

iichel said:
short somewhere else in the wiring loom

Or another module that's clamping the K-line high for some reason.

Since this is essentially an Mk.3 car still, it has very few modules. Engine, auto-Trans (if equipped), ABS, Airbags, Radio, and Immo are about it. Since the ABS module is being dodgy, I'd consider it a prime candidate.

-Uwe-

Uwe · Jun 9, 2018

DDanielson said:
That sounds like a plan. I’ll have to pull fuses until the +12 on K1 goes away.

Disconnecting modules one by one is the more traditional approach.

DDanielson said:
I haven’t gotten far enough in the process yet to even register the vin with Ross-Tech, much less scan the vehicle.

I doubt this car knows its own VIN, so there might not be anything to register.

DDanielson said:
It might be easier just to push it off a cliff but I kind of love it. It’s been a relatively trouble free car up to this point.

Then you'd have to replace it with a newer car that would be even more complicated to work on.

-Uwe-

DDanielson · Jun 11, 2018

So far I’ve ruled out the ABS module, Airbag module, and the radio. One thing I noticed is that pins 4 and 7 of the OBD port have 9v when the car is off. Is that normal?

Uwe · Jun 11, 2018

DDanielson said:
One thing I noticed is that pins 4 and 7 of the OBD port have 9v when the car is off. Is that normal?

Huh?

Pin 4 is supposed to be Ground!

-Uwe-

DDanielson · Jun 11, 2018

Yep, pin 4 is ground and 7 is carrying +9v.

Uwe · Jun 11, 2018

DDanielson said:
Yep, pin 4 is ground and 7 is carrying +9v.

The voltage on pin 7 is "indeterminate" without a load on it. The drivers in the control modules are "open collectors" and the tester (plugged into the OBD-II socket) provides the pull-up resistor.

Try putting something like a 1 kΩ resistor between pins 4 and 7 and then measure the voltage.

-Uwe-

Jack@European_Parts · Jun 12, 2018

J0ccglEycgjNLN9e88x5uFjWUhiFyEUY167X5xDcOlFoWRizCuUa8K7kU7y0IQOQmjdHP1NV8T6sghE2nkJIzTza vrcLi0tKyKIIw6kXvc2HhWVoWRRBG9 L1VXHxKXcm z9M6czBIH sgAAAAABJRU5ErkJggg==

STOP!

Please ground the harness to the floor through the air bag module and if this module is bad and not plugged in you get no K line for the others.

Genius design right!

DDanielson · Jun 12, 2018

Uwe said:
The voltage on pin 7 is "indeterminate" without a load on it. The drivers in the control modules are "open collectors" and the tester (plugged into the OBD-II socket) provides the pull-up resistor.

Try putting something like a 1 kΩ resistor between pins 4 and 7 and then measure the voltage.

-Uwe-

With a 1K resistor there’s 7.9v on Pin 7.

DDanielson · Jun 12, 2018

I’ve found a brown wire hanging from the dash. No idea where it goes yet but it has 9.86v on it with the key off. I can’t post photos but I can email one if it’ll help.

Uwe · Jun 12, 2018

DDanielson said:
With a 1K resistor there’s 7.9v on Pin 7.

A 1K resistor to ground should pull the K-Line very close to ground, assuming of course that there's no tester plugged into the OBD-II port providing a pull-up.

DDanielson said:
I’ve found a brown wire hanging from the dash. No idea where it goes yet but it has 9.86v on it with the key off. I can’t post photos but I can email one if it’ll help.

Please see: How to Post Pictures.

-Uwe-

DDanielson · Jun 12, 2018

https://imgur.com/gallery/5ubk7Na

Uwe · Jun 12, 2018

A brown wire with a big ring terminal on it...

I can't imagine what that would be other that a ground wire that someone neglected to attach to a ground point at some time...

-Uwe-

Jack@European_Parts · Jun 12, 2018

Please check the TV connector on top of the fuse box.

This is used for bridging the K line from DLC to components or check if some idiot plugged in an unwarranted track to the TV slot causing an issue ........

DDanielson · Jun 13, 2018

Uwe said:
A brown wire with a big ring terminal on it...

I can't imagine what that would be other that a ground wire that someone neglected to attach to a ground point at some time...

-Uwe-

I still have no idea what it is but I grounded it to the tunnel and the voltage on it and the K1 line went down to 3.63 v. Placed a resistor between pins 4 and 7 and the K1 voltage went down to 0.10v. Now the car starts and stays running. Could it be the ground for the immobilizer?

Uwe · Jun 13, 2018

DDanielson said:
I still have no idea what it is but I grounded it to the tunnel and the voltage on it and the K1 line went down to 3.63 v. Placed a resistor between pins 4 and 7 and the K1 voltage went down to 0.10v. Now the car starts and stays running. Could it be the ground for the immobilizer?

I don't know if it's the ground for the immobilizer, but it sure sounds like it's the ground for the OBD-II socket, so have a look at the wiring diagrams and see what else shares that ground point.

-Uwe-

K1 Short to +12 Factory Radio

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