Gee, wonder why the Auto trans was in limp mode? (Caution, many graphic images)
09-18-2007, 04:18 PM
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Gee, wonder why the Auto trans was in limp mode? (Caution, many graphic images)
First, let me start by saying that I bought this '96 A4 knowing that it has transmission problems after the PO drove through a deep puddle. It is in otherwise great shape, with 78K miles.
My first order of business was to research like mad on this forum, and I learned a lot about water damage to the TCU. I know that water can enter the cabin and footwells through a number of seals along the firewall, especially if the drain hole under the battery tray is clogged and if the lower windshield cowl water deflectors are eaten up. Well, this car had all those issues. In addition to the deep-puddle excursion that the PO felt compelled to make, well, I knew water was going to be a problem.
The second order of business was to order a VAG-COM from Ross-Tech. I haven't even successfully used the thing yet, more info in a moment, but Andy at Ross-Tech has already been very helpful. Andy, if you're reading, I think I found the problem.
I remedied all of the drains and seals under the hood and along the firewall. I used the AC evaporator line post in the A4 FAQ as a guide for a lot of it (thanks, whoever you are). I sealed up the rubber bellows that the heater core inlet and outlet pass through (this was just hanging, thanks PO). The battery tray drain was so clogged that after a light rain, there was about 2" of water standing under the battery. The windshield cowl water deflectors are munched, with no sealing against the windshield. The little rain gutter that goes at the base of the windshield to funnel water away from the cabin air inlet was just flopping around, not held in place. So yeah, there were a lot of ways for water to get in.
After that, today was 'pull the passenger seat and get to diggin' day. I got the door trim off and wrestled the carpet up to see a scene of horrors.
Now, mind you, everything on the car works and the interior has been dry as a bone for the entire 3 weeks I've had the car (all electrical systems work, I've tested them all). The car RUNS AND DRIVES, in limp mode of course. The only symptoms I had were limp mode, obviously, and a VAG-COM error that the K1 line "shorts to ground." So I couldn't get VAG-COM to pull the codes, I called Andy at Ross-Tech and he said that error can be caused by any one of the controllers for a module being faulty or shorted out. Like I said, I think I found it.
Behold, the horror:
I pulled back the carpet and pulled a dripping TCU box out of the soggy hole:
<img src="http://img440.imageshack.us/img440/5240/dsc06715sp1.jpg">
This little seal for the hole in the bottom of the floorboard was nice and snug:
<img src="http://img230.imageshack.us/img230/3351/dsc06716gk2.jpg">
My first peek into the "black box":
<img src="http://img440.imageshack.us/img440/4042/dsc06717dr7.jpg">
Water and sludgy slimy poo were just pouring out:
<img src="http://img230.imageshack.us/img230/4595/dsc06718cy2.jpg">
Slightly moist:
<img src="http://img230.imageshack.us/img230/2125/dsc06719kx7.jpg">
Another view:
<img src="http://img230.imageshack.us/img230/3508/dsc06720fr6.jpg">
At least I can still read the label:
<img src="http://img230.imageshack.us/img230/5002/dsc06721lo9.jpg">
Hmm...doesn't look right:
<img src="http://img230.imageshack.us/img230/4663/dsc06722fk2.jpg">
It makes a sloshy sound when I move it:
<img src="http://img440.imageshack.us/img440/3550/dsc06723gl2.jpg">
Probably not making good electrical contacts:
<img src="http://img440.imageshack.us/img440/1416/dsc06724rf1.jpg">
Looks like the sludgy poo is trying to get out:
<img src="http://img72.imageshack.us/img72/7925/dsc06725gw5.jpg">
Wire harness is a little dirty:
<img src="http://img72.imageshack.us/img72/4954/dsc06726gz8.jpg">
More wires:
<img src="http://img72.imageshack.us/img72/5000/dsc06727vm6.jpg">
Not looking good:
<img src="http://img72.imageshack.us/img72/263/dsc06729qt3.jpg">
Then I opened her up. All of the metal tabs holding the TCU together broke off with only a feather's touch, I'd say they were a little bit weakened by prolonged submersion.
Short to ground, indeed:
<img src="http://img72.imageshack.us/img72/1716/dsc06730tf4.jpg">
Probably not going to just dry out and be all better:
<img src="http://img230.imageshack.us/img230/2276/dsc06731gb5.jpg">
Yikes:
<img src="http://img440.imageshack.us/img440/3315/dsc06732qa3.jpg">
So, I'm going to source a used TCU, dry this **** out for a few days, clean all the electrical contacts with tons of DeOxit, and hope for the best. In all honesty, I think a new TCU will get me all the way back. If not, I'll keep tracking down the components one by one until she's running like a champ.
Hope you enjoyed the carnage.
My first order of business was to research like mad on this forum, and I learned a lot about water damage to the TCU. I know that water can enter the cabin and footwells through a number of seals along the firewall, especially if the drain hole under the battery tray is clogged and if the lower windshield cowl water deflectors are eaten up. Well, this car had all those issues. In addition to the deep-puddle excursion that the PO felt compelled to make, well, I knew water was going to be a problem.
The second order of business was to order a VAG-COM from Ross-Tech. I haven't even successfully used the thing yet, more info in a moment, but Andy at Ross-Tech has already been very helpful. Andy, if you're reading, I think I found the problem.
I remedied all of the drains and seals under the hood and along the firewall. I used the AC evaporator line post in the A4 FAQ as a guide for a lot of it (thanks, whoever you are). I sealed up the rubber bellows that the heater core inlet and outlet pass through (this was just hanging, thanks PO). The battery tray drain was so clogged that after a light rain, there was about 2" of water standing under the battery. The windshield cowl water deflectors are munched, with no sealing against the windshield. The little rain gutter that goes at the base of the windshield to funnel water away from the cabin air inlet was just flopping around, not held in place. So yeah, there were a lot of ways for water to get in.
After that, today was 'pull the passenger seat and get to diggin' day. I got the door trim off and wrestled the carpet up to see a scene of horrors.
Now, mind you, everything on the car works and the interior has been dry as a bone for the entire 3 weeks I've had the car (all electrical systems work, I've tested them all). The car RUNS AND DRIVES, in limp mode of course. The only symptoms I had were limp mode, obviously, and a VAG-COM error that the K1 line "shorts to ground." So I couldn't get VAG-COM to pull the codes, I called Andy at Ross-Tech and he said that error can be caused by any one of the controllers for a module being faulty or shorted out. Like I said, I think I found it.
Behold, the horror:
I pulled back the carpet and pulled a dripping TCU box out of the soggy hole:
<img src="http://img440.imageshack.us/img440/5240/dsc06715sp1.jpg">
This little seal for the hole in the bottom of the floorboard was nice and snug:
<img src="http://img230.imageshack.us/img230/3351/dsc06716gk2.jpg">
My first peek into the "black box":
<img src="http://img440.imageshack.us/img440/4042/dsc06717dr7.jpg">
Water and sludgy slimy poo were just pouring out:
<img src="http://img230.imageshack.us/img230/4595/dsc06718cy2.jpg">
Slightly moist:
<img src="http://img230.imageshack.us/img230/2125/dsc06719kx7.jpg">
Another view:
<img src="http://img230.imageshack.us/img230/3508/dsc06720fr6.jpg">
At least I can still read the label:
<img src="http://img230.imageshack.us/img230/5002/dsc06721lo9.jpg">
Hmm...doesn't look right:
<img src="http://img230.imageshack.us/img230/4663/dsc06722fk2.jpg">
It makes a sloshy sound when I move it:
<img src="http://img440.imageshack.us/img440/3550/dsc06723gl2.jpg">
Probably not making good electrical contacts:
<img src="http://img440.imageshack.us/img440/1416/dsc06724rf1.jpg">
Looks like the sludgy poo is trying to get out:
<img src="http://img72.imageshack.us/img72/7925/dsc06725gw5.jpg">
Wire harness is a little dirty:
<img src="http://img72.imageshack.us/img72/4954/dsc06726gz8.jpg">
More wires:
<img src="http://img72.imageshack.us/img72/5000/dsc06727vm6.jpg">
Not looking good:
<img src="http://img72.imageshack.us/img72/263/dsc06729qt3.jpg">
Then I opened her up. All of the metal tabs holding the TCU together broke off with only a feather's touch, I'd say they were a little bit weakened by prolonged submersion.
Short to ground, indeed:
<img src="http://img72.imageshack.us/img72/1716/dsc06730tf4.jpg">
Probably not going to just dry out and be all better:
<img src="http://img230.imageshack.us/img230/2276/dsc06731gb5.jpg">
Yikes:
<img src="http://img440.imageshack.us/img440/3315/dsc06732qa3.jpg">
So, I'm going to source a used TCU, dry this **** out for a few days, clean all the electrical contacts with tons of DeOxit, and hope for the best. In all honesty, I think a new TCU will get me all the way back. If not, I'll keep tracking down the components one by one until she's running like a champ.
Hope you enjoyed the carnage.
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09-18-2007, 04:51 PM
#9
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I had the EXACT same issue with my old car and had to remove/replace 6.5 FEET of harness!
I have pics of the carnage, it was major.
You will need to replace all the wires as well I will bet LOTS AND LOTS of $$ on it.
I bought a used TCU from a salvage yard and had them send me the wire harness too. The only sent me about 1.5 feet of it even though I asked for at least 4-5 feet. GET AS MUCH AS YOU CAN!
The harness goes up and over the trans hump about mid way near the e-brake and then over up and under the dash over by the fuse block. I had to remove both front seats and then the carpet on both sides... separated the TCU harness from the rest of the wires (that was pretty easy) then just kept on cutting the wire harness until I had good clean wire with no evidence of ANY corrosion. No corrosion, no discoloration, no weak wires, only clean bright shiny copper. I cut so much out (most of the way to the dash!) that I decided instead of splicing every single one of those little wires and creating another source of trouble I moved the harness under the dash instead of across the floor and then mounted the TCU/box unit under the dash near the heater/glove box. A MUCH SAFER PLACE.
Anyway, long story short it worked fine. The TCU wires/harness/connectors are VERY VERY sensitive to resistance so if there is any corrosion or weak wire in the harness it will continue to throw codes until you remove ALL the bad wire and CORRECTLY splice in new ones. My harness for what it's worth didn't "look" anywhere near as bad as yours, but I kept having major limp issues after replacing the TCU and cleaning the harness/connectors, finally had to do this whole wire splice and all was well again....... GOOD LUCK! ;-(
If you need help feel free to email me or post up on here.
You will need to replace all the wires as well I will bet LOTS AND LOTS of $$ on it.
I bought a used TCU from a salvage yard and had them send me the wire harness too. The only sent me about 1.5 feet of it even though I asked for at least 4-5 feet. GET AS MUCH AS YOU CAN!
The harness goes up and over the trans hump about mid way near the e-brake and then over up and under the dash over by the fuse block. I had to remove both front seats and then the carpet on both sides... separated the TCU harness from the rest of the wires (that was pretty easy) then just kept on cutting the wire harness until I had good clean wire with no evidence of ANY corrosion. No corrosion, no discoloration, no weak wires, only clean bright shiny copper. I cut so much out (most of the way to the dash!) that I decided instead of splicing every single one of those little wires and creating another source of trouble I moved the harness under the dash instead of across the floor and then mounted the TCU/box unit under the dash near the heater/glove box. A MUCH SAFER PLACE.
Anyway, long story short it worked fine. The TCU wires/harness/connectors are VERY VERY sensitive to resistance so if there is any corrosion or weak wire in the harness it will continue to throw codes until you remove ALL the bad wire and CORRECTLY splice in new ones. My harness for what it's worth didn't "look" anywhere near as bad as yours, but I kept having major limp issues after replacing the TCU and cleaning the harness/connectors, finally had to do this whole wire splice and all was well again....... GOOD LUCK! ;-(
If you need help feel free to email me or post up on here.
