trenity8

Okay, 2008 Audi A4 avant. 2.0
Threw a code P0688 - ecm communication failure. Car wouldn't start for about 35 minutes then just started and has been fine since.

Took it in for 75k service and asked them to check the codes.
They said there were 2 relays that had moisture damage and needed to be replaced. ($580). I said I'd do it just needed the part numbers.

I got these, 4H0951253A. They didn't tell me location but figured I could find out where these were in the car (got the parts overnight pedal for $53 total)
The back of them says 645, I thought they were the ones under the ecm but those (2) say 615 and have a part number of 8E0951253.

Can some lay this bag of snakes out straight or tell me where they are located cause I've pulled the dash, the wipers and ecm box - called - 10 places and searched google 50 times... seems that the 2 part numbers are interchangeable and would make sense being under the ecm but - cautious on just randomling replacing relays not being sure about compatibility.

Any help would be awesome!

Dwes

Went to genuineaudiparts.com They've got a helpful tool where you can just search for part number. Here's the diagram where it popped up:


4H0951253A is listed as part #2

Says it's a vacuum pump relay. Kinda weird because a P0688 Code is related to a damaged or defective ECM relay, but the 8E0951253 part number is for a "multi-purpose" relay. Looks like they're listed mostly for running the fuel pump. Kinda sounds like the stealership was trying to sell you parts you don't need. If you haven't noticed any issues then I wouldn't worry about the relays. Generic P0688 info:

https://www.yourmechanic.com/article...by-parker-hill

Hope this helps.

-Dave