My check engine light on my '99 V70 had been on for about 7 months. Yes, I know that's bad, but my mechanic said it was a defective catalytic converter. As a broke college student living in a state with no regulated emission standards, I've had to ignore it until I can afford to fix it. Any thoughts on why it's suddenly turned off? I restarted my engine several times today, and it still hasn't come back on.

 

The Check Engine light wlll reset if the battery is disconnected long enough.

 

If the CAT was bad, you would have noticed loss of power, rattling noise or rotten egg smell from the tail pipe (the 3 general symptoms of a failing CAT). However, the ECU (Electronic Control Unit: on-board computer that controls the engine, transmission, ABS, etc...) may have picked up out-of-spec signal from a sensor.

I would visit an auto parts shop such as Autozone and have them run the free diagnostic (called OBD-II: OBD stands for On-Board Diagnostic). They will hook up a hand-held scanner that can "talk to" the computer in your car and report if fault code has been set.

I hope this helps.


JPN

 

Good idea, I'll take it to Autozone. Thanks!

 

If the engine computer does not see the fault for a certain amount of drive cycles it will shut the light off but the code should still be present.