Category Archives: automotive

Audi Q7 4.2L Base BAR engine codes

The car started to idle rough, sometimes it would shut off, other times it was difficult to start. The EPC and CEL(check engine light) were both on. To prevent the car from laboring too much I would have to keep it in neutral at stops.

The following two codes(P0171, p0174) were remedied by replacing the PVC valve that is located near the firewall above the throttle body. You will need a T27 or T30 star bit to get it out. It is in a tight space. Took me about 45 minutes.



The following code(P0129B) was remedied by bending the metal contacts inside the connectors to the two high pressure fuel pumps. Once I had gotten this code previously because of a blown fuse in the engine bay fuse box located under the hood, on the drivers side just below the windshield. It was one of the blue 15 amp fuses. Its best to check the fuses and connectors before replacing these high pressure pumps because they are expensive. This took about 2 hours of trail and error, swapping relays, testing the regulator/solenoid coil continuity, battery connections, etc.


The following (P0300)code was remedied by changing the PVC valve, the ignition coils and spark plugs. The issue arose because the bad PCV valve caused oil to build up in the spark plug wells and reduced the quality of the connection between the ignition coil and spark plug. I could have simply cleaned the connectors on the coils and the plugs and this would probably have been good enough. I would suggest using a lot of dielectric grease when putting the coils in as it keeps some of the motor oil from getting into the space between the coils and plugs. I forgot to put grease on the ignition coil harness connectors…… Before buying a whole set of ignition coils. I would try to clean the connectors inside.


I found the best deal on the OEM NGK spark plugsĀ  and no frills ignition coils on I cant recall where I purchased the PVC/breather box as it took me a year after buying it to install it. If you have the time and the freedom(#MGTOW) just address a CEL/EPC light immediately or other problems will develop. Those of us on the plantation do not have that luxury and end up spending thousands for the dealer to do a simple fix.


Featured photo: Tennen-Gas [CC BY-SA 3.0 (

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