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Hello Audi community. I am posting this issue I am having on my 2012 Audi A6 3.0 with 80K miles in hope to find others that are or had the same issue and bring this to the attention of NHTSA. I have already filed my complaint and need more of you to do the same. Audi needs to recall this car in my opinion.
ON THIS CAR, THERE IS AN INTERNAL TRANSMISSION COOLANT VALUE THAT IS PART OF THE COOLING SYSTEM AND OBVIOUSLY, THAT COMPONENT ALSO HELPS KEEP THE TRANSMISSION TEMPERATURE IN CHECK. THE ISSUE WITH THIS DEFECTIVE PART IS THE VALVE MALFUNCTIONS CAUSING COOLANT TO PENETRATE THE TRANSMISSION CONTROL MODULE AND FROM THERE INTO THE WIRING HARNESS. WHEN THIS HAPPENS, IT IS A CATASTROPHIC MALFUNCTION OF THOSE COMPONENTS AND A POTENTIAL FIRE HAZARD. WATER AND ELECTRICAL DO NOT MIX WELL. THE ESTIMATE FROM AUDI IS $14,000 TO FIX IT. $6,500 IN PARTS AND $7,500 IN LABOR. ABSURD!
THE ROOT OF MY ISSUE IS THAT THERE IS NO WAY TO DETECT THAT THERE IS A PROBLEM WITH THE AUTOMOBILE UNTIL THIS MAJOR MALFUNCTION HAPPENS. IF THAT WERE NOT THE CASE, THE CONSUMER COULD AT LEAST HAVE THE CHANCE TO HAVE THE CAR SERVICED PREVENTING THIS HUGE EXPENSE AND POTENTIAL FIRE HAZARD. I HAVE AN EMAIL FROM THE SERVICE MANAGER ADMITTING THIS IS THE CASE.
IN MY CASE. THE CAR RAN FINE. THEN JUST WENT HAYWIRE. THE SERVICE MANAGER SAID COOLANT GOT INTO THE CONTROL MODULE AND “FRIED” THE MODULE AND WIRE HARNESS. THIS IS A VERY SERIOUS ISSUE WITH THIS CAR. AUDI HAS TURNED ME DOWN TWICE TO FIX THIS POTENTIALLY COMBUSTIBLE PROBLEM EVEN WITH ME OFFERING TO HELP IN THE EXPENSE. VERY SCARY.
THE PICS BELOW ARE FROM ANOTHER A6 WITH THE SAME ISSUE.
ANYONE ELSE OUT THERE WITH THIS ISSUE AND HOW DID YOU RESOLVE IT??
Al, VAG refers to this problem as "coolant migration". Not the first incident, of course. It's been going on for a while. People were finding pink coolant in their tail lights!
Not limited to A6 - check out the tech service bulletin
I discovered the same problem on my A5 (80K miles, 2013)
The problem showed up when I was driving and had sudden loss of power.
My ECU had water in the connector and shorted out the signals to the coils. I cleaned it up and it worked again but I needed to track down how it happened so I went to an Audi dealership
The guys at Prestige in Denver were very helpful even though I was there just asking questions about my DIY.
They pulled the connector at the coolant valve and showed me how it is fried.
As you are aware there is a TSB and a recall on the A8 for this problem.
I made my complaint to the N H T S A.
The fix for me is to replace the valve, the connector at the valve, and route new wires parallel to the old wires. and I Hope that the cleaning I did of the ECU terminals and harness will stay good enough.
See the thread by IknowHuhA6 OBDII Code P2753 for a useful list of parts.
T S B 100 585 74 - 8951
When I was at the dealer and they told me that the transmission coolant valve was likely the culprit I was pretty confused.
My car has a proper manual transmission, it didn't make sense to me that it would have a cooler for the transmission - never seen that on a manual before.
Thank you for the info. Good to hear you are on the way back to getting your car repaired. I will be towing my car to an independent shop to start my $6,200 repair. Hopefully more will file a complaint with the NHTSA. Then I need to decide to sell it or drive it to recoup the expense. It is a wonderful car when it is running. Now it is just a 4K LB paperweight.
Photos don't help much. Where is this valve and connector located? I am getting ready to replace transmission fluid in my 2012 A6 3.0. Also, where there indications of coolant loss at the coolant overflow tank?
I found the pictures online from a post with an issue similar to mine. The connector is on the side of the transmission per the tech. should be very visible. I have had this car for 6 months and have not been under it yet. There were no signs of an issue. When the auxiliary coolant pump goes, it wicks coolant down the harness to the connector and then the TCM so there was no puddles. If you check your auxiliary coolant pumps and pull the connector and find no coolant, you should be good.
Wow, I didn't see that someone started a new thread on this, I have been fighting this for over a month and I just posted in the original P2753 thread. Typically, what fails is not the auxiliary but the transmission coolant valve (N509). You can only access it from under the car. I have attached instructions and a diagram of where it is.
I am also going to quote my other post here in the hopes that someone has come across this issue but without any signs of coolant leakages.
This view is from under the car looking up towards the driver's side front wheel well. This would be again from outside the driver's door/wheel well.
Originally Posted by dctech
My 2012 A6 3.0T with the ZF8HP55 (US) started throwing this code (P2753) about a month ago. Based on the information I gained here, I went ahead and replaced the N509 valve (4H0-121-671-D) and the 2-pin wiring harness (1J0-973-702). There was no evidence of coolant leakage at the valve or at the 16pin connector for the mechatronics board from the transmission. I've cleared the code several times and it comes back immediately (no engine start required, just ignition on).
Next, I have checked pin1 of the 2 pin connector on the N509 and I see that I have continuity to SA13 (fuse in panel A) and that it is indeed supplying 12v. I have also checked that pin 2 from the N509 has continuity with pin 15 from the 16 pin mechatronics connector.
My next planned steps are to bench test the old N509 valve to ensure that it was actually still working when I pulled it, and eventually make sure that the new one I installed is also still working.
Has anyone experienced this issue and it not be the N509 valve? From the circuit diagrams and coolant flow diagrams, it is the only plausible issue, but I have addressed it and no luck so far.
Thank you for the info. I will share it with my Tech. Suppose to tow the car there on Monday. My transmission is the NXT. Not sure if the ZF and NXT are one in the same.
Cannot believe there has not been a recall. Please file your issues with the NHTSA if you have not already done so. We need everyone to file to get Audi to move on this.
Just did my transmission fluid over the weekend at 100k. Checked the connector. Everything looks good, No coolant, connectors are just like new, no sign of any coolant anywhere around that area.
05-16-2019, 02:01 PM
A6 TCU Fried Due To Coolant Control Valve Issue
