Another k1 short to ground...please guide me

[drywaller]

I am getting the K1 short to ground with my VCDS. I have scoured the net for the best way to address this and the conclusion I have come to is that it may be easiest to unplug modules until I find the culprit. Assuming it is a module. Problem is I have no idea where the different modules are. Can anyone give me an exact location of the modules on my 2005 TDI MK4?
Thanks for any and all help.

 

[drywaller]

I should also add that recently my heater core decided to start leaking. Nothing too serious. I just keep the temp on cold and I am good to go as far as smelling coolant goes. However today I noticed that I am getting coolant on the passenger side floor. Could this have contributed to the K1 short to ground issue?

 

[gatz]

Just to be clear, the car runs but its a no comm? Is the K-line actively shorted to ground or just disconnected? You would check that with a test light. If its actively shorted, water intrusion / coolant leak from your heater core could be the issue if its gotten into the connectors.

I did a little more looking at the wiring diagrams, and from my understanding, the OBDII port K-line wire only connects directly to the instrument cluster and the radio. The instrument cluster appears to act as a communications hub for the rest of the cars modules. Someone correct me if I am missing something on these diagrams.

Data link connctor K-line 16 pin OBDII connector, pin 7 green/white wire spices at A76 "Connection (K-diagnosis wire) in instrument panel wiring harness" to:
- J285 - Instrument Cluster Control Module, blue 32 pin connector, pin 25
- Radio - 8 pin connector, pin 3

That's all that wire directly connects to. If there is an actual short it has to be in that area. I would pull the radio as my first step.

 

[Vince Waldon]

Do you have the original radio or an aftermarket?

 

[drywaller]

Original radio. Car is bone stock in every way. I pulled that radio with no change in K1 short. I also unplugged the heater controls since I was already there. The coolant leak is minimal and does not appear to have migrated to any electrical compoents. The coolant has collected on the floor board where the wire bundles run next to the center console on the passenger side.

 

[drywaller]

I also unplugged the air bag module and the seats. I will try the cluster today.
I want to say thanks for replying. When it comes to car wiring my mind seems to shut down. I am not sure why as I can work on anything g else with great success. Wiring just seems to overwhelm me.
Thanks again for the help.

 

[drywaller]

Just to be clear, the car runs but its a no comm? Is the K-line actively shorted to ground or just disconnected? You would check that with a test light. If its actively shorted, water intrusion / coolant leak from your heater core could be the issue if its gotten into the connectors.

I did a little more looking at the wiring diagrams, and from my understanding, the OBDII port K-line wire only connects directly to the instrument cluster and the radio. The instrument cluster appears to act as a communications hub for the rest of the cars modules. Someone correct me if I am missing something on these diagrams.

Data link connctor K-line 16 pin OBDII connector, pin 7 green/white wire spices at A76 "Connection (K-diagnosis wire) in instrument panel wiring harness" to:
- J285 - Instrument Cluster Control Module, blue 32 pin connector, pin 25
- Radio - 8 pin connector, pin 3

That's all that wire directly connects to. If there is an actual short it has to be in that area. I would pull the radio as my first step.

Yes, car runs and drives and everything works as it should. I have zero idea if it is an active short or just disconected. I have to assume it is shorted because if it was disconected from a module wouldn't that particular module just not show up on VCDS?

 

[gatz]

I would use a test light or resistor+amp meter to determine if that line is truly being hard (to either +12 or ground.) If you determine its not being driven hard, perhaps your VCDS cable is at fault or the connection at the connector is poor.

The Ross Tech page seems to indicate the cluster should be driving the K-line to +12V with a high impedance (weak) pullup.

There is some info regarding this: http://www.ross-tech.com/vag-com/aftermarket-radio.html

 

[gatz]

Also did you double check all your fuses are good? I've seen that mentioned in a few posts about this.

 

[drywaller]

Checked the fuses. Pulled them out 1 by 1. All looked good. I also removed the cluster. Still getting the short message.
Can you provide more detail as to how to test the K1 curcuit with a test light?

 

[gatz]

The K1 should be a high impedance signal, so it should not provide enough power (or ground) to make a test light light up bright. Although it might glow very dimly.

- With test light connected from battery to K line: if it lights, K line is providing a hard short to ground
- With test light connected from ground to K line: if it lights, K line is providing a hard short to battery

The test described on the Ross Tech site is doing basically this, but in an alternative way.

Do you currently get a voltage on that line (multimeter from ground to OBDII pin 7), and if so what value?

Edit: The line could also be severed, in which case the test light would also not light. You would check for continuity with a multimeter from the OBDII plug pin 7 to the pin 25 on the cluster connector.

 

[drywaller]

Than you for this info. When I get more time I will do some testing. The cluster is easy enough to get out so we. Time permits I will follow your suggestions.
Thanks again.

 

[D-cappz]

What was the verdict on this short to ground? Having same issue with my dad's car, cannot connect with VCDS or any other scanner I have.

 

[fly360]

I had this same issue. My VCDS was reading K1 short to ground. I swapped instrument clusters with another one of my Mk4 VWs and was able to read the car's ecu and other modules. Now my problem is finding out if the instrument cluster can be repaired or if there is a way to swap out with a used one being though I am unable to get any info(codes) off of the old one. My car has the stock radio which threw me for a good puzzle trying to figure it out. I am posting this so if someone else has this problem maybe it will help them out and to see if anyone has ideas on what to do from here. Also if you remove the cluster and don't put one in its place the VCDS will think everything is ok but won't be able to read anything. The Bentley manual has a wiring diagram 74/4 that will show this circuit.