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Old December 30th, 2009, 17:07   #1
03PlatinumBug
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Unhappy TCM got wet...help!

I need some help!
2004 Passat TDI...we were in the mountains and it snowed, then froze, then rained, then froze again. Somehow, water poured into the passenger foot well and FLOODED the TCM. (Sunroof track, battery drain...not sure yet)
The car went into limp mode, but I managed to remove the water and get the car home to Florida. We now have an airbag light and a P0706 code (transmission range sensor-implausible value).
The TCM seems to be OK as does the harness. I have thoroughly cleaned everything with contact cleaner and dried the carpets, insulation, floor pans, etc. There's almost no visible corrosion on the pins. However, the PRNDL display is in reverse video, there is no overdrive, the tiptronic is disabled, and the hole shot off the line is very slow. (in other words...Limp mode)
I don't think the range sensor is damaged...I think this is still something to do with the water intrusion.
So....
Any ideas on why I still have an airbag light and how to further troubleshoot the range sensor error?
Thanks!
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Old December 30th, 2009, 19:23   #2
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Read fault codes with VCDS. Once you know what they are, then you can start to repair without guessing.
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Old December 30th, 2009, 19:53   #3
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Quote:
Originally Posted by 03PlatinumBug
I need some help!
2004 Passat TDI...we were in the mountains and it snowed, then froze, then rained, then froze again. Somehow, water poured into the passenger foot well and FLOODED the TCM. (Sunroof track, battery drain...not sure yet)
The car went into limp mode, but I managed to remove the water and get the car home to Florida. We now have an airbag light and a P0706 code (transmission range sensor-implausible value).
The TCM seems to be OK as does the harness. I have thoroughly cleaned everything with contact cleaner and dried the carpets, insulation, floor pans, etc. There's almost no visible corrosion on the pins. However, the PRNDL display is in reverse video, there is no overdrive, the tiptronic is disabled, and the hole shot off the line is very slow. (in other words...Limp mode)
I don't think the range sensor is damaged...I think this is still something to do with the water intrusion.
So....
Any ideas on why I still have an airbag light and how to further troubleshoot the range sensor error?
Thanks!
There's a positve splice connection internal to the TCM wiring harness under the passenger side carpet. Open up the wiring harness and make sure that connection is not corroded and it solid. Positive from that connection goes to the multifunction transmission range switch. The same positive also feeds the airbag control module.
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Old December 31st, 2009, 19:11   #4
03PlatinumBug
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Thanks for the help. Unfortunately, my VW mechanic is on vacation until Monday and I won't have access to his VCDS until Monday.
I will check out the splice at first light tomorrow. Sounds promising!

Thank you!
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Old December 31st, 2009, 19:24   #5
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On other thing while I'm thinking about it. There should be a ground connection near the passenger side a-pillar (can't remember exactly where). Follow the harness back to the dash and a-pillar and look for it. Make sure that connection isn't corroded.
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Old January 1st, 2010, 14:36   #6
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I found a splice in a green wire with a red tracer. No corrosion...splice was in great shape.
I did not find any grounds under the A-Pillar cover...just a big junction block with a lot of plugs. But, no water damage as the water did not get that high.
I also crawled underneath to take a peek at the transmission sensor...squeaky clean in there to my surprise.
I'm starting to get a bad feeling this is going to wind up being a new TCM...ick. That will be $$$.
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Old January 1st, 2010, 15:18   #7
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Quote:
Originally Posted by 03PlatinumBug
I found a splice in a green wire with a red tracer. No corrosion...splice was in great shape.
I did not find any grounds under the A-Pillar cover...just a big junction block with a lot of plugs. But, no water damage as the water did not get that high.
I also crawled underneath to take a peek at the transmission sensor...squeaky clean in there to my surprise.
I'm starting to get a bad feeling this is going to wind up being a new TCM...ick. That will be $$$.
I looked at the wiring diagram. That's a connection for the cruise control. There should be at least 2 other splices - the positive splice is all black wires with one wire originating from the 3 pin brown connector in the right a-pillar and a ground splice (multiple brown wires). The ground terminates at a ground connection in the lower part of the right a-pillar. It seems to me that others have said it's near the floor and towards the dash.

What you are experiencing is a fairly common problem when the floor gets flooded and it generally does not kill the TCM. If you don't have access to a VCDS to scan the TCM and clear codes, you can try to reset the TCM by removing the battery ground cable for a few minutes and then reconnecting. Sometimes that will get the TCM out of the emergency running mode (limp mode).
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Old January 1st, 2010, 17:29   #8
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Would the "ground connection" be like a ring terminal on a post or some other type of hardware? I would expect some path back to the battery negative using a larger wire.
That harness is fairly busy so knowing what kind of hardware I'm looking for would be extremely helpful!
Thanks for your help!
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Old January 1st, 2010, 17:42   #9
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I don't know the specifics on the Passat, but on my A4 Jetta, the
airbag controller was bolted to the hump underneath the center stack
below the dash. To remove an airbag code, I sent the entire controller
to Airbagsystems.com and for about $100 they cleared the code.
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Old January 1st, 2010, 18:48   #10
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Quote:
Originally Posted by 03PlatinumBug
Would the "ground connection" be like a ring terminal on a post or some other type of hardware? I would expect some path back to the battery negative using a larger wire.
That harness is fairly busy so knowing what kind of hardware I'm looking for would be extremely helpful!
Thanks for your help!
Yes, that's the ground connection. The path back to the battery is the metal chasis of the car not a wire.

One more thing, are the gears PRND432 being displayed. If not then the problem could be a communictaion error or the TCM is fried. You need to hook up a VCDS and see if it can communicate with the TCM. And if the gears are being displayed, does the display follow as you shift from P to R to N to D? If yes, the multifunction switch is probably okay and the TCM is at least communicating.

Last edited by Plus 3 Golfer; January 1st, 2010 at 19:08.
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Old January 3rd, 2010, 09:24   #11
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Plus 3,
Yes the PRND432 is displayed, but in reverse. But no, the display does not follow as you shift. However, I thought that was the designed operation once the TCM is in limp mode.
If the TCM were not communicating, I think I would pick up some serial errors on the scan tool and a CEL. But I only have the range sensor DTC and the airbag fault.
It's too cold to continue today, so I'm going to drop it off tonight for VolksWurks to work on it tomorrow. Hopefully, the VCDS can clear everything out!
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Old January 3rd, 2010, 10:51   #12
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If the problem is not related to the TCM knowing the gear, then the actual gear will follow as you shift but in reverse video. So it's looking more like wiring or the switch since the TCM reported the DTC and is probably working okay. BTW, was there water inside the TCM box? If not, then that's a good sign for the TCM to be okay.

Hopefully, VolksWurks has seen water intrusion issues before because I know of people that have replaced their TCM just suspecting a bad TCM or had the dealer diagnose a bad TCM only to find out later that it was either latent moisture / corroded connections causing the problem and were unable to get a refund for the TCM.

If it does turn out to be the TCM, look for a used one. You can probably find one for less than $300.
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Old January 5th, 2010, 17:08   #13
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Well,
The bad news is...it's the TCM. They cracked it open after checking the switch and it was "green and fuzzy" in his words. Not a good description for any electronics.
So...anyone know where I can get one of these TCMs in the $300-500 range? It's a 3B0 927 156 AP (Bosch P/N is 0260002879). eBay had none...much to my surprise.
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Old January 5th, 2010, 18:11   #14
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Have you tried cleaning the TCM board, drying and reinstalling? That has worked for others.

If it's green and fuzzy, you've probably have had water issues for a while. Have you found and fixed the water ingress? Make sure both fresh air plenum drains are clear - one under the battery and the other under the brake booster, test your sunroof drains by pouring water in the sunroof channels and see if the water drains out the front and rear drains, and lastly check your pollen filter to see if the seal is intact.

I'd call a salvage yard. They should be able to locate one nationally. People have picked them up at salvage yards for a couple of hundred $.
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Old January 6th, 2010, 18:27   #15
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I was thinking of dousing it with contact cleaner and trying to clean it up as best as I could. Can't hurt at this point, right?
I'll try the salvage yard option. I found one online for $595...that's the best so far.
Any ideas what the differences in the AS or AM versions of this TCM are vs. the AP version that I have? I know the AS and AM (and AA) come from gassers, so I assume the shift points are different. Any idea if these could work? (because these I can get readily for low $$$)
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