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I recently bought an 03 S6 and taking care of some needed and put-off maintenance.
I have a check engine light throwing a few different generic codes (just ordered VCDS and will confirm those codes once received), and the gear selector dash lights are all lit rather than just the one for which the car is shifted into.
Upon pulling the TCM I found that there is definitely water damage, with a lot of corrosion throughout on the connectors, plus an added wire tapping two points on the board. Needless to say, I'm going to replace the TCM for one in good condition. I'm looking for a used one since 1) new ones are $1500+ and 2) I have plans to swap n 01E in once repairs and maintenance are up to date. I need to get the car smog'd to register and need the CEL cleared beforehand in order to pass.
The question: My TCM has part # 4B0927156FH, and I am seeing part # 4B0927156EQ as a replacement (or vice versa). Is that the case? are these interchangeable?
I know it's only the last two letters that change between all the C5 platform TCM variants and that none are interchangeable, but these two seem to be the exception.
Another question: Below are images of my wiring harness for the TCM. This is nest original? feels hard to believe, but hope it wasn't tampered with.
CEL is going to be emissions related. Start looking for vacuum leaks. Might also be secondary air pump. If you cruise by an Autozone, or other auto parts store they will usually be willing to do an OBD II scan free of charge. This will pull codes for the CEL and give you a starting point. VAG Com scan is essential for scanning other systems and components like ABS, TCU, etc.
VAGCOM comes today, so I'll update you with CEL codes.
Also, I had a better look at the nest of wires. I found a picture of someone elses which was very clean, but did have the wire connector. Except for the 4 black wires going into the connector, everything is continuous with no splicing.
I think I'm going to buy a TCU ending in EQ and see if it works.
I received my "EQ" TCU and plugged it in. I now have more/different fault codes and think the driveability is affected whereas it wasn't on the "FH" one. I haven't cracked open this new one, but was told it was never affected by water.
And here are the Fault Codes with the new "EQ":
-------------------------------------------------------------------------------
Address 01: Engine Labels: Redir Fail!
Part No: 4D0 907 560 CN
Component: 4.2L V8/5V G 0001
Coding: 06752
Shop #: WSC 02325
VCID: 74B1DD4BA7A8DC078A5-5160 WAUXU54B03N036626 AUZ7Z0B2107341
1 Fault Found:
18032 - MIL Request Signal Active (Check TCM for errors too!)
P1624 - 35-00 -
Readiness: 0110 1101
-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 01L-927-156.lbl
Part No: 4B0 927 156 EQ
Component: AG5 01L 4.2l5V USA 1010
Coding: 01002
Shop #: WSC 02325
VCID: 7AADF37385CCAA77D09-5160
5 Faults Found:
18171 - Shift Lock Solenoid (N110)
P1763 - 35-10 - Open Circuit - Intermittent
18155 - Transmission Solenoid Power Relay
P1747 - 35-10 - Open or Short to Ground - Intermittent
17090 - Transmission Range Sensor (F125)
P0706 - 35-00 - Implausible Signal
17094 - Transmission Fluid Temp Sensor (G93)
P0710 - 35-10 - Malfunction - Intermittent
18237 - Pressure Control Valve 4 (N218)
P1829 - 35-00 - Open or Short to Ground
I found an FH TCU (replacing my water-damaged FH), and seller said it was tested and worked. I plugged it in and the CEL cleared, but just for a second. By the time I tried driving it the CEL came back on and drivability is not affected. It feels like it's locked in 4th or 5th gear, from a stop and doesn't ever shift.
I believe the seller when it says it was tested and confirmed to work properly. So, I'm having a hard time trying to understand why my water-damaged unit, although rigged to work properly, throws a code, but the clean unit throws a code and DOESN'T work properly.
I thought maybe the pigtail/harness was affected but then why would the water-damaged unit function properly? Anyone have any info there?
Or is there any chance that a previous owner recoded something to make the rigged water-damaged unit work? And then requiring me to recode back to normal to make a good unit work properly?
I just pulled the TCU and harness connector apart. Looks like it has been tampered with.
There is a wire soldered to the board. Then there is what looks like a red wire with the pin pulled out and covered with a shrink sleeve. No way this is original, right?
And then there is one clearly corroded and is the pin that corresponds to rigged wire on the board.
This continues to get more interesting/frustrating.
Your car has definitely been messed with in the past. Cobbling these cars together rarely has a good outcome. There has very obviously been water incursion in the past. In the second photo the green residue on the red wire is evidence of a poor connection and water damage. This is similar to the green "growth" that occurs on battery terminals. There is an outside chance that repairing that connection/ wire might solve at least part of your issue. I don't have a manual so can not help identify what circuit that is. The first photo shows a lot of oxidation on the board probably compromising some circuits. If you are going to fix this, I would suggest 1) get a wiring diagram for your car, 2) get a replacement TCM 3) get a replacement connector for the TCM and wire it properly. I would hazard a guess that a previous owner cobbled up the wiring repair to get the car running but the replacement TCM would not work with those alterations. The replacement TCM you bought might work if the wiring issues get straightened out first.
04-29-2019, 10:11 PM
S6 TCM/TCU Part Number
