Error codes

Q I now need help with an issue with a 2004 VW Beetle 1.6 Convertible. It has an ongoing issue which brings up various error codes – most commonly these two: P0172 System Too Rich Bank 1 – P0101 Mass or Volume Air Flow A Circuit Range/performance. I have tried replacing the MAF with an genuine part and it made no difference. On one occasion after deleting the above codes I then got a Crankshaft Position Sensor error – but that never came back after deleting it. However, P0101 and then P0172 keep reappearing.

I can’t find any vacuum leaks or other Maf-related errors and at least one O2 sensor was replaced fairly recently at an MOT. In addition, the car doesn’t run smoothly. On start-up the revs drop almost to a point where the car stalls before picking up again and the idle isn’t as smooth as it should be. Peter Robinson A The codes P0172 system too rich bank 1 Intake blocked, and P0101 Mass air flow (MAF) sensor/ volume air flow (VAF) sensor - range/performance problem, are both related to air volume problems and this can often be a blocked or leaking pipe in the induction area.

As you have replaced the MAF sensor with no improvement and as you have also checked for any vacuum leaks, the next area I would check is the EVAP canister purge valve. This is located in the EVAP canister in the offside inner wing, and if the valve is stuck open and leaking it will give the same symptoms as a vacuum leak from the manifold.

Other causes of the P0172 code and the rough running may be too high fuel pressure (although this would also trigger a fault code), weeping injectors or an 02 sensor which has been renewed.

Given the regular problems I have come across with the EVAP cannister purge valve, this would be the most likely cause of the problem.