Sjorge3442

Leaving the store yesterday the CEL popped up on my b9. P2681 / 15462- Engine Coolant Bypass Valve Control Circuit/Open. Seems like this is related to coolant leaking from the water pump and corroding the sensor connector? Does anyone know which sensor connect this is? My WP hasn't really leaked too much and I've never had to put coolant in my car since I got it in March of 2021, but I'm thinking this may have been a long time coming and I just need to clean the connector.

SMac770

The water pumps on the B9 have an electrically actuated solenoid for better temp control. You might look into the coolant pump warranty extension / class action / whatever it ended up becoming for the B9 to see if this would be a relevant situation.

So this is a B9.0 that was new to you in Mar '21, or a new B9.5 with an in-service date of Mar '21?

https://www.ecstuning.com/b-ina-part...6l121111j~ina/
Using this since it was the first useful hit that came up. Fourth pic, the electronic module is in the front and you can see the plug to the lower right of the front end. The motor itself is sticking up to the left.

The electrical connection to the N493 "actuator for engine temperature regulation" is a 5-wire connection all direct to the J623 engine control module. It's possible it's an issue with one of the wires or connector; more likely an issue with the N493. Assuming it's unchanged from the B8.5 Gen3 CNCD engine:
pin 1 - angle sensor ground from ECM
pin 2 - angle sensor voltage output to ECM
pin 3 - angle sensor 5V power from ECM
pin 4 - actuator motor ground from ECM
pin 5 - actuator motor 12V power from ECM

Something like that. Best guess until someone provides validated info.

Sjorge3442

Thank you for this! For reference, this was a new to me 2017 a4 as of Mar '21. The orientation of the water pump makes it tough to see anything with the throttle body still installed so I think I may pull that off and see what's going on once I get a better shot at the water pump. Thanks for sharing the location of that plug. I had seen a few videos/articles that it's a connection issue due to leaking coolant/corrosion so I'll start there first and see what happens. I came across a few references of people who paid dealers to replace water pumps only for the CEL to remain on until the connection was cleaned/replaced. If it's water pump time, I'll likely handle this myself and knock out some intake valve decarbing at the same time.

Sjorge3442

Just wanted to come back and say I had the N493 fail on me this weekend. Left a gas station and the car immediately went into limp mode and limited me to 4k RPMs, but I couldn't even get the car to rev that high. Pull off into a parking lot and watched the temp gauge rising so I shut her down and called for a tow. Thankfully I was relatively close to home. New WP+Thermostat is in the mail already. Seems like there is no solid written resource for how to do the repair on the B9's so I'll likely write something up for the community since this seems to be an inevitable repair everyone will have to do at some point. The process seems VERY similar to the B8's, but I know I like model-specific information, so hopefully, it can help others out in the future.

SMac770

All of the proper processes are in the workshop manuals. erwin.audiusa.com, pay for a day, get all the PDFs for your VIN.

S4'ed

There are YouTube videos showing how to replace the waterpump/temp control unit on a MK7 GTI.

Sjorge3442

So I ended up swapping the thermostat housing and water pump this past weekend. I didn't take any photos or anything as the workshop manuals have the steps laid out. The three biggest tips I have for this inevitable job are:

1. You need a T-30 that's NOT a 3/8' drive socket. The 3/8" socket is too chunky to get to the top left bolt on the housing. I used a 1/4" drive bit which worked perfectly. I supposed that this is why the workshop manual specifies a VAG specialty T-30.
2. Use a mirror for the bottom thermostat housing bolts. I don't know why, but I was having the hardest time getting the torx bit on the bottom right housing bolt, but as soon as I used a mirror, it was super easy.
3. My lower radiator hose didn't have a traditional petcock to drain the fluid - just an x-slotted plastic bolt. I tried messing with it for a moment but then decided against potentially stripping/breaking it and simply pulled the lower coolant sensor out of the house and drained the coolant that way.

Other than that, it's super straightforward and a lot easier than I had anticipated. probably a 5 out of 10 on the hardness/difficulty scale, but anyone with moderate wrenching skills should be fine doing this job. It took me about 3.5-4 hours in total, but I was taking my time. Having done the job now, I think this would be a sub 2-hour job. Happy to answer any questions for anyone else doing the job, just shoot me a PM!

S4'ed

So, did you remove the intake manifold and/or the throttle body?

Sjorge3442

Intake manifold - no. Throttle body - yes. Once the throttle body is off and the coolant tank is out of the way, there's a ton of room. No need to pull the intake. I didn't have any of the tools/supplies on hand to do a carbon cleaning so I chose to not take the intake off. Now, if you're looking to do both at the same time, the job would be even easier.

SMac770

Seems they got rid of the drain opening, no doubt another cost cutting move. The manual says to lift the clip on the lower radiator hose and pull it off the radiator to drain coolant now.