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Discussion Starter #1
Hello R8'ers,
Last week I replaced the leaking expansion tank on my '12 V8. After replacing it, I took it for a test drive and all types of errors popped up on the dash and the car didn't run great at all. Got back home and noticed I forgot to plug in the harness (pictured below circled in red). The reason I unplugged it was to get better access to the screw (also in the pic that's circled in red). I plugged it back in and the car ran great and all errors disappeared except the CEL. I plugged in my OBD2 and cleared the code to see if it would pop up again later. Well it did and I got a code reading of P0421. Is this something that was caused by not plugging in that harness? And if so, what could have made the CEL come on because of it being temporarily disconnected?

Thanks in advance!

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