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I just finished a lengthy DIY on my 2012 A6 3.0T Prestige with 108k miles and I would like to share some information. The issue starts with a bad TSC coolant valve and ends with coolant inside the mechatronic connector mounted on the side of the transmission. Apparently coolant can wick inside the wire from the TSC valve to the mechatronic connector. I'm a Chemical Engineer/ retired Professional Automotive Engineer and past ASE Certified Mechanic and I can definitively state that I have never seen this type of failure before. I repaired the TSC valve and it's connector based on VAG-COM code (P2753) and then ran into a follow-on code two days later (P1894). The dreaded 'Transmission Communication Error' - you can continue to drive. Dealership offered an $11,000 repair, yes $11,000!!
There was a TSB on the TSC valve and this repair should/ would have been covered under warranty but what infuriates me is that Audi has made the decision to NOT correct a $200 part that can lead to a $11,000 repair. I would have authorized repair for the original TSB at my cost during one of my regular service visits if I had known the implications. Poor customer / long term ownership relationship building by Audi.
Ok - I didn't pay $11,000. I took my car home mad at Audi and my dealership but still happy with the car and decided to fix myself. I started with an inspection of the mechatronic connector. My TSC must not have leaked for very long and corrosion was minimal. I used two paper towels and 10 Q-tips and carefully cleaned and dryed both sides of the connector. I reassembled with ample dielectric grease, I did two or three connector mounts/ dismounts to work the grease in and the car has functioned perfectly without any codes or warnings for the last three days.
I did price out the repair if I needed to change the mechatronic and I estimated $1,200 using a used mechatronic unit ($3,200 new).
My reason for writing this post is to warn A6 owners of the problem. If I read this post prior to the TSC valve error I might have changed it right away. Below are the parts I bought (from another post) to repair/ replace the TSC valve AND I highly recommend opening and inspecting the mechatronic connector to clean / lubricate with TSC valve replacement or as regular service.
TSC repair:
1 4H012167D Transmission Oil Cooler, Solenoid Valve $111.60
1 000979019EA Wires $10.85 (this wire has the two 'female pins attached at either end, cut in the middle and it give you the necessary two replacement wires)
1 1J0973702 Housing $9.70 2 000979940 Connector $2.88 (these are crimp sleeves for connecting the new wire - i did not use these. I soldered the wires)
Things I ran into not listed in the other repair posts:
The TSC valve is under the two underbody pans and one support brace. My car spent most of it's life in Michigan and there were/ are two areas that game me problems.
1) The three screws in the middle of the two removable underbody shields were extremely rusted and all three broke off. There is no access to the tops of these fasteners as they are inside a subframe crossmember. I ended up drilling and tapping and using the same fasteners (triple square) from the front shield (3) N90896202. I drilled small and tapped them out with a punch - pretty easy. Sorry i didn't document the thread size.
2) The underbody support brace bolts were very rusted. I used ample WD-40 and worked them in/ and out several times to get them out without breaking. Someone said they broke these in the original thread. I would NOT have wanted to drill and tap these as they are much larger fasteners. I bought eight replacements and reinstalled with liberal anti-seeze (6) N91174101 and (2) N91174201.
3) The new connector pins and housing do not have the same 'seal' on each pin as the original factory parts. I installed the pins and then used some black RTV to seal off the top of the connector prior to installation. Don't put in too much as you still need to remount the corrugagted sleeve.
4) I cut open the heat shield covering about 4 inches up from the connector to give me room to solder and then folded the wires back inside and zip tied the heat shield back around the wiring.
And of course .... clean out and dry the mechatronic connector before reassembly!!!
Awesome repair. Wish you were near me, I have a 2012 3.0T as well and had the P2753 code. I tried to get Audi to replace the valve when I went in for the fuel rail recall and they acted like the TSB didn't exist. Then quoted me over $300 to replace it with me providing the part. I ended up doing it myself with the car on jackstands (PITA@!!#) I only replaced my valve and didn't do the wiring. My car has 54K and while there was some liquid in the connector it didn't look corroded. I used CRC electrical contact cleaner and sprayed it in the connector, replaced the valve and added dielectric grease on the pins to make sure. After a couple weeks I haven't seen any more codes and hopefully there was no damage to the mech unit.
I'm glad you haven't had the second code. That said I would highly recommend the same cleaning procedure on the mechatronic connector. You can get at it by just removing the rear underbody shield and not the support brace. You cannot see into the male (transmission) side of the connector but you have access to clean. I used Q-tips and then tore half the cotton off the tips of Q-tips to get in-between the tighter pin positions. I know its a pain to lift and get under there but the downside is costly.
Still no new codes but my plan is to get in there and clean it again in two weeks. I really want to see if more fluid has wicked. Still cannot believe I just typed that!! The valve replacement eliminates the source but there might still be fluid in the wires.
PS. My dealership service manager called and suggested he would approach Audi USA to cover my repair. I told him what I'm doing and he was very interested in what my results are down the road. Apparently he just quotes the Audi template 'under warranty' repair charge for this condition. He suggested he has some leeway with vehicles out of warranty and if my repair works he is willing to try it if the pins are not corroded on future repairs.
Going through the same issue on my first Audi 2012 A7 105,000 miles. In Michigan as well. Thanks for sharing. I was quoted over $8000.00 from the dealership. Reached out to Audi customer service 3 days ago. Still waiting to hear back. Hopefully, I will hear something soon. I met with the mechanic today and he showed me where the coolant had gotten into the wiring. Luckily, doesn’t appear to have gotten into the ECM, but they are not sure about other areas yet.
I have heard enough horror stories this year about this valve so...I'm replacing mine on my 2012.
I have the parts and this post reminds me I have three weeks before vacation and I need to install it.
I haven't been underneath the car in a while, and I need to change the oil and filter as well.
I plan on checking for leaking motor mounts, condition of the flex pipe, leaks, etc.
I will also check the condition of the wiring harness connectors.
good write up, also did a DYI on this, but i rewired as well, just to be safe.. takes about 30min extra and gives me peace of mind
clocked 2000km since fix and still going strong
Glad my information is helping. I believe the major repair as quoted by the dealerships can only be avoided if the mechatronic connector has not corroded to the point of deterioration. This is the large connector on the side of the transmission and the root of the major issue once the fluid wicks from the TSC valve. As stated above EVERYONE with a 2012 should change the TSC valve AND inspect the Mechatronic connector. My connector was wet but only had slight 'greening' on one or two posts inside the connector so cleaning and dielectric grease was an option. Before embarking on the major repair I would definetly clean / dry / lube the connector, reinstall and check function.
My car is now at 117k miles so I've gone roughly 10k with no codes or malfunctions. I'm planning to change the transmission fluid at my next service interval (125k) just in case and coolant wicked inside the trans. No functional trans issues present.
Note: after TSC valve replacement and then after the Trans Malfunction code the last symptom which drove action on my part was an audible noise out of the left front speaker. Each gear would emit a different noise out the speaker - not too loud but present. My wife thought the transmission was failing. Wicking fluid in wires / wet trans connectors sending interference through the audio system / $1500 thermostat replacements. Love my A6 but Audi needs to work on serviceability as a more prominent part of their vehicle development plans.
I just finished a lengthy DIY on my 2012 A6 3.0T Prestige with 108k miles and I would like to share some information. The issue starts with a bad TSC coolant valve and ends with coolant inside the mechatronic connector mounted on the side of the transmission. Apparently coolant can wick inside the wire from the TSC valve to the mechatronic connector. I'm a Chemical Engineer/ retired Professional Automotive Engineer and past ASE Certified Mechanic and I can definitively state that I have never seen this type of failure before. I repaired the TSC valve and it's connector based on VAG-COM code (P2753) and then ran into a follow-on code two days later (P1894). The dreaded 'Transmission Communication Error' - you can continue to drive. Dealership offered an $11,000 repair, yes $11,000!!
There was a TSB on the TSC valve and this repair should/ would have been covered under warranty but what infuriates me is that Audi has made the decision to NOT correct a $200 part that can lead to a $11,000 repair. I would have authorized repair for the original TSB at my cost during one of my regular service visits if I had known the implications. Poor customer / long term ownership relationship building by Audi.
Ok - I didn't pay $11,000. I took my car home mad at Audi and my dealership but still happy with the car and decided to fix myself. I started with an inspection of the mechatronic connector. My TSC must not have leaked for very long and corrosion was minimal. I used two paper towels and 10 Q-tips and carefully cleaned and dryed both sides of the connector. I reassembled with ample dielectric grease, I did two or three connector mounts/ dismounts to work the grease in and the car has functioned perfectly without any codes or warnings for the last three days.
I did price out the repair if I needed to change the mechatronic and I estimated $1,200 using a used mechatronic unit ($3,200 new).
My reason for writing this post is to warn A6 owners of the problem. If I read this post prior to the TSC valve error I might have changed it right away. Below are the parts I bought (from another post) to repair/ replace the TSC valve AND I highly recommend opening and inspecting the mechatronic connector to clean / lubricate with TSC valve replacement or as regular service.
TSC repair:
1 4H012167D Transmission Oil Cooler, Solenoid Valve $111.60
1 000979019EA Wires $10.85 (this wire has the two 'female pins attached at either end, cut in the middle and it give you the necessary two replacement wires)
1 1J0973702 Housing $9.70 2 000979940 Connector $2.88 (these are crimp sleeves for connecting the new wire - i did not use these. I soldered the wires)
Things I ran into not listed in the other repair posts:
The TSC valve is under the two underbody pans and one support brace. My car spent most of it's life in Michigan and there were/ are two areas that game me problems.
1) The three screws in the middle of the two removable underbody shields were extremely rusted and all three broke off. There is no access to the tops of these fasteners as they are inside a subframe crossmember. I ended up drilling and tapping and using the same fasteners (triple square) from the front shield (3) N90896202. I drilled small and tapped them out with a punch - pretty easy. Sorry i didn't document the thread size.
2) The underbody support brace bolts were very rusted. I used ample WD-40 and worked them in/ and out several times to get them out without breaking. Someone said they broke these in the original thread. I would NOT have wanted to drill and tap these as they are much larger fasteners. I bought eight replacements and reinstalled with liberal anti-seeze (6) N91174101 and (2) N91174201.
3) The new connector pins and housing do not have the same 'seal' on each pin as the original factory parts. I installed the pins and then used some black RTV to seal off the top of the connector prior to installation. Don't put in too much as you still need to remount the corrugagted sleeve.
4) I cut open the heat shield covering about 4 inches up from the connector to give me room to solder and then folded the wires back inside and zip tied the heat shield back around the wiring.
And of course .... clean out and dry the mechatronic connector before reassembly!!!
04-03-2019, 09:37 AM
Coolant in Mechatronic and TSC connectors
