I have a V40 2001 and my check engine light started going on and off intermittently for three months. I read the code with my code reader (INNOVA 3100 OBD II), runs about $100 if you shop around. The only problem with this code reader and all others is that it can only read generic codes (p0) series and not the Volvo priority (p1) codes. My code reader said the problem was a p0130 code = bad oxygen sensor. Being that my car is under warranty I brought it in to the stealership to have it diagnosed and repaired. What they said that it was also showing a Volvo priority code “Code 16”. They said that there was a TSB stating that ECU should be reprogrammed and updated with a new engine managment program when experiencing this code. All this for $80.00 not under warranty. However the good part is that the check engine light went out and stayed has out after the ECU reflash. My fuel economy went up and the transmission ha been shifting more smoothly as a result.

Aaron

2001 V40
1997 850 sedan