Hi, I have a 2001 VW Passat 4 cyl. turbo that has a check engine light on. The codes are:
P0172-Bank one, fuel measuring sys. too rich
P0171-Bank one, fuel measuring sys. too lean
Sounds to me like an O2 sensor, but there is no code indicating a problem.
Both trouble code correcrive action codes have to check the pressure regulator first under the correcrtive action. Do the pressure regulators go bad on VW's.
Thanks!!Optional Information: 2001 Volkswagen Passat 4cyl turboAlready Tried: only scanned car, cleared codes and they returned.
If I read those two codes off a Passat my first thought would be to replace the O2 Sensor. I don't believe the pressure regulator would be as likely to cause both 171 and 172.
This is something that is tough to diagnose from web posting because, as you mentioned, these codes don't indicate the source of the problem they just indicate the problem.
The O2 sensor would seem like your best bet and would be the first thing I'd check if working on your car.