[hb1017]

Hey,

I have a 2001 s40 that I have been driving for the last two years with minimal problems. Recently I got a check engine light and noticed the car was not running that well - idle at really low RPM, poor pick up. I took it to the mechanic, he read a p0172 and decided to change the engine thermostat. I drove the car for about ten miles and the check engine light returned, this time it read a p0101. The mechanic told me I could continue to drive it for a couple days before bringing it back to him. As I drove the car the check engine light would go away for a bit and then come back, this cycle continued a couple times. After having the mechanic take a look at it again he said he needed to clean the MAF and everything should be fine. I drove it out of the mechanics shop and the acceleration was much better. Five miles down the road I got the check engine light again decided to take it back to the mechanic. On the way back, the car stalled and I had to restart it at a red light. The mechanic pulled the code reading p0163, he said to drive it for a few days and see what happened. Anyone have any clue what may be going on here or what needs to be changed or looked at? I have a smog check for renewal coming up so I need to figure out what is going on here.

I greatly appreciate any help/advice you guys might have.

Thanks!

 

[sulley007]

You probably have a bad O2 sensor.

 

[hb1017]

The car stalled this morning and has been giving me bad gas mileage.. is that consistent with a Bad O2 sensor? Also, how do I figure out which sensor has gone bad??

 

[BHart]

Probably a bad O2, if that's what the code shows. There are many other general possibilites; really dirty air filter, bad plugs, cat plugged, dirty gas. Depends on the mileage of the vehicle and how it's been maintained.

A shop with a proper Volvo diagnostic computer should be able to check codes to isolate the problem.