Category Archives: audi

Audi Q7 4.2L Base BAR engine codes(Revised)

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. I updated this posting in red. 

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. Under further inspection these codes are caused by a split hose. A leaky vacuum hose connected to the intake. 



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. After replacing my High Pressure Fuel Pump at the tune of about $300 I found this issue is related to the solenoids. Under the driver’s side wind sheild wiper there is a fuse box. One section is easy to open with plastic knobs, the back of it has to be removed using torx bits. I saw a solenoid number 614 in both sections. I swapped them around and this code went away.


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. This was caused by the solonoid mentioned above. 


I found the best deal on the OEM NGK spark plugs  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.

If you need to access Qudi Q7 4.2 Manuals I found a few by digging around online and have uploaded them here: Audi Q7 4.2 Manuals

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

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