TCM got wet...help!

03PlatinumBug

Member
Joined
Mar 30, 2008
Location
Gainesville, FL
TDI
2003 Beetle TDI
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!:confused:
 

MOGolf

Top Post Dawg
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Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
Read fault codes with VCDS. Once you know what they are, then you can start to repair without guessing.
 

Plus 3 Golfer

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Oct 29, 2008
Location
ARIZONA
TDI
Und tschüss! 2009 Jetta 12/23/2012
03PlatinumBug said:
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!:confused:
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.
 

03PlatinumBug

Member
Joined
Mar 30, 2008
Location
Gainesville, FL
TDI
2003 Beetle TDI
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!
 

Plus 3 Golfer

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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.
 

03PlatinumBug

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Mar 30, 2008
Location
Gainesville, FL
TDI
2003 Beetle TDI
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 $$$.
 

Plus 3 Golfer

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03PlatinumBug said:
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).
 

03PlatinumBug

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Joined
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Location
Gainesville, FL
TDI
2003 Beetle TDI
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!
 

Hamman

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Oct 4, 1999
Location
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No TDI's, but an '84 Rabbit diesel
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.
 

Plus 3 Golfer

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Und tschüss! 2009 Jetta 12/23/2012
03PlatinumBug said:
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:

03PlatinumBug

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Joined
Mar 30, 2008
Location
Gainesville, FL
TDI
2003 Beetle TDI
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!
 

Plus 3 Golfer

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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.
 

03PlatinumBug

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Joined
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Location
Gainesville, FL
TDI
2003 Beetle TDI
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.
 

Plus 3 Golfer

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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 $.
 

03PlatinumBug

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Location
Gainesville, FL
TDI
2003 Beetle TDI
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 $$$)
 

MOGolf

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underneath something
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2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
AP was used in 2004 and CF in 2005. The programming for the gassers would be completely wrong and fuel economy would be poor (assuming it doesn't cause fault codes and limp mode).
 

03PlatinumBug

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Gainesville, FL
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Well, for those who peruse these forums looking for answers like I do...here's how the situation finally worked itself out. I could not find a used TCM anywhere even though every salvage yard on the planet insisted they "had the part and were ready to ship" in their emails when in fact they hadn't even looked at the part. I wound up shipping the TCM to Auto and Truck Electronics in TN who stored the software, ripped the guts out of my TCM, replaced it with their own reverse engineered guts, and restored the software. They turned it around in 2 days and it worked like a charm. Ran me about $400 after shipping and everything else and it works like a champ now. I'm very happy with these guys.
 

03PlatinumBug

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Location
Gainesville, FL
TDI
2003 Beetle TDI
Further update...
Well, it turned out that Auto ECU actually did NOT fix it. It was beyond repair. The tranny started acting up again and we eventually learned that extended time in limp mode had burned up the tranny. They did refund my money less shipping so I'm still quite satisfied with their service and would recommend them.
 
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