Thursday, wifes car failed the Virginia emissions test because the check engine light wouldn't come on when the key was turned. No other reason. I thought maybe the bulb was burned out, but my wife took a short drive today and said it came on on the way home. I went out and turned the key, and of course it didn't come on. Is it possible that the bulb is going bad and causing this intermittent problem? What other possible causes?

 

Bad connection at bulb? Tust try removing bulb and reinserting or better just change the bulb and reconnect all the connectors in the back of the gauge/warning light cluster. If that does not solve your problem then you may have an issue at the ECU, again redo all connections at ECU. If it's anything more than a bad bulb or conenction you may have your hands full.

 

I'll give this a try tomorrow. I was afraid someone would say I might have my hands full.

 

It's just that it's kind of a strange problem and if it does not have a simple cause such as listed above, then it may be difficult to repalr.

 

funny socket/connection.

 

Sometime my 4th gen will just throw a code, then it will clear after a few days. Sometimes it's Evap canister stuck open, sometimes other stuff. Just take the test when there is no SES.

 

Thats pretty much your answer right there.

 

Bulbs come on and go out on their own a lot with OBDII. You could have a monitored system that is BEGINNING to fail, or is INTERMITTENTLY failing and when it does the light comes on. Then when the computer runs its OBD checks during the next drive cycle, the system might be working again, so it turns it off.

The computer CAN and WILL turn the light OFF for certain systems that it monitors if they are working during the next check. For instance, if there is a leak in the EVAP system (ie if you forget to tighten your gas cap), this will throw the Check Engine Light, but if you get out and tighten it, the computer will run the EVAP System check during the next drive cycle and realize that there is no leak, and turn the light OFF.

Try to run the self-diag check on the computer the next time the light is on to see what might be starting to malfunction, then go from there......

Good Luck

 

if not the bulb then yeah its your connection.