K1 short, disconnected tcm, now tranny limp home mode

An 03 Auto Jetta set for 8 months due to a pump issue. I swapped the pump, car started and ran very well. K1 short on all modules and in troubleshooting that, I disconnected the ABS module, no change. Disconnected the TCM Module, no change, but, tranny is now in limp mode. Since I can't communicate with the TCM, I think I'm screwed and stuck with limp mode until I find the bad module. Or, will driving it help the tranny relearn the shift points ? Has anyone run into this before and have a solution? I am miles from my shop and don't have my Bentley. Does anyone have a link to the other module locations? Thanks.

SRS is under the middle of the dash, below the heater case, bolted to the tunnel.

Radio is smack in the middle of the dash.

Instrument cluster is... well... you know...

I don't think anything else would/could cause that, problem is, once the Cluster is unplugged, you won't be able to communicate anyway, but 2003 should be using a paired CAN bus wire for that.

If you plug the TCM back in, does the transmission work normally?

Maybe I am not understanding what/how/where your meaning of "K1 short". Can you explain that a little better? If the car starts and runs, then obviously both the Instruments (and the CAN Gateway and immobiliser contained within) as well as the Engine controller are working.

Vcds can't communicate with any module, says k1 is shorted to ground. I just pulled the TCM harness orff of the module, checked for bent pins, everything looks good, I'm putting it back together now. Same transmission condition, will not start off in 1st unless manually selected.

New change, disconnected battery again, discharged capacitance, hooked it back up, vcds program options, test, now shows interface found (same as before) but now k1 and k1 are OK, CAN: not ready.

still unable to communicate with any module. All fuses are good, everything looks normal, but the car isn't talking to vcds. Just tested vcds on my b4 and it works there.

On that car K1/K2 OK and CAN not ready would be normal.

Can you communicate with the Gateway? Or just nothing at all?

Nothing at all.

I would think you either have a problem in the Instrument Cluster, or in the K-wire between the DLC and the Cluster. But like I said, on that car, the CAN Gateway should have its own paired HI/LOW wires from the DLC to the Cluster.

Pins 6 and 14 of the DLC are the HI/LOW CAN, pin 7 is the K line. I think the K gets spliced in there too, not sure exactly where all it goes though. Mid-2002 change to the Double DIN radio means those are on the CAN bus and not using the old K-line, but I think the TCM still might on the ALHs.

Well I take that back, looks like the TCM is using the CAN bus, too. At least, it has a pair from the Gateway (which is inside the Cluster) too.

Can you try using the OBD2 generic side of VCDS? It will JUST access the generic side of the Engine, but...

I'll try that when I get back.

Unable to connect using the obdII option, says vehicle is not obdII compatible. Also, now the test function under vcds options is reporting k1 is shorted again. I haven't done anything since yesterday when K1 was reported as OK.

I asked the customer again what he did during the 8 months the car sat due to leaking injection pump. He said he replaced the 109 relay and checked the fuses and nothing else, besides jumping the car a few times due to a dead battery. I believe him telling me that the cel wasn't on while he drove it for 2 years, so the cel came on during the
months it sat from something he did, or something nature did such as corroded terminal somewhere, mouse damage, etc. But.... I don't see any evidence of that so far.

ninedee_golf_tdi said:

.......................... He said he replaced the 109 relay and .............................

Click to expand...

I'd look at that, I bet you have a spare sitting around. The only other thought I had was a botched radio install (miswired).

I'm learning about the k-line (thanks Jimmy) and was prepared to cut the k-line at the tcm and wire it to a temp obd connector, but rain happened. Tomorrow for that. I did swap the 109 but that didn't help.

For modules using the can bus, is that the signal path vcds uses for reading codes, etc ? Or is that still done on the k line ? Why do the modules have both ?

PROGRESS: I cut the k line at the tcm and wired it to a temp obdII connector on pin 7, along with ground on pin 4 and battery on pin 16. I could then access the tcm with vcds. There were no codes on the first try, on second try there was NO COMM WITH ENGINE, cleared that, went for a spin and tranny is working correctly again. I dont know why the tranny lost its mind, but life is getting better.

So, can I find the k line in the ecm and the abs, and wire that to the tcm k line and only have vcds monitor those three ? At least until I have time to find the offending module giving me the k1 short to ground ?

Thanks again Oilhammer and Jimbote.

MORE PROGRESS: I have the ecu and tcm tied together in my temp obdII connector, and now can scan both engine and tranny. I disconnected the abs module in a previous test and determined the k1 short is not originating there. The now clearable cel was for start of timing which was crazy advanced from changing the IP in the field and no way to set the timing. I think I'll leave well enough for now, finish the wire splices and put it together. I know there is a common point in the harness where all the k lines get tied together, but does any one know where that is ?

I *think* the K-line splice from the DLC is in the dash harness somewhere. It does show a splice between the DLC and the Instruments, but I am not sure exactly where it goes.

The later (2000+) ALH cars are sort of 1/3 of the way to CAN, and they seem to have both K and CAN interlaced here and there. I know for sure the radio communication changed middle-2002 when they went from the single to double DINs, but not sure about the other modules.

More oddness: I successfully isolated and combined the tcm and ecu k-lines and ran them to the temp obdII connector. For giggles, before I reassembled the under dash plastics, I tested the original obdII connector, and although the vcds red lamp flashed throughout the test, I successfully ran an auto scan and it found each module less the tcm and ecu. Hmmmm.... I reconnected those two k-lines to the original obdII connector, and vcds found everything, but with the red light still flashing. It was chilly in SC that day, about 40'ish. I wonder if temperature is having anything to do with this ?