bo2006

Nice write-up, I am in the process of doing this on my 2012 A6, when I took the sub-frame piece of metal off to get access to the area, I snapped a couple of the bolts, they were all rusted.
In-case anyone else is doing this, these are the bolts to order, I guess you are supposed to replace them when you remove that piece.
2 bolts - N91174201
6 bolts - N91174101

thanks everyone for sharing the pics and info. Saving me a trip to the Dealer, I just hope my TCV isn't damaged.

jpjmustang

this tread was great
replaced the valve - the connector was still good

Thanks everybody

LMSI-G35X

I'm looking to replace these parts as I just got this error code on a 2012 A6 w/ 54K.

This part is listed as a heater control valve or coolant shut off valve, I'm just curious why this throws a transmission error?

redwolfmendoza

Hey man,

I was wondering this myself when I was fixing this on my A8 - I thought I needed a new tranny!

I checked and there's a small blocky radiator under the engine/at the front of the drivetrain which two hoses similar to the ones on solenoid valve go into. So, my guess is that the ECU (computer) uses the solenoid valve as a kind of thermostat to activate the transmission cooler.

Can anyone confirm?

bo2006

That's correct, its a transmission cooler thermostat/solenoid, opens and closes to cool the transmission.
My plug isn't perfect after I replaced the part, from all the corrosion of the coolant, but I have driven 500miles without an error, so fingers-crossed my Magtronics unit is ok.

LMSI-G35X

makes sense, thanks. Is it recommended to use the cable type hose clamp pliers for this or do the normal type pliers work?

bo2006

Normal pliers removed the clamps.

richbusta2

Can anyone help me with the wiring? I bought the yellow pin wires and housing, but I need to make sure I connect the correct pin number to the colored wires. What color goes with pin #1, and same for pin #2? I cut my wires and now I'm confused.

Thanks,
Rich

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.

Saabya6

Can anyone shed any input? I had the solenoid replaced by an indy, but when connected, it makes a terrible loud buzzing sound, as if the pump is going to die out.. I had it disconnected in the mean time.