My Jetta Failed inspection, because “the check engine light isn’t working.” The light is not lit, but there are four codes stored (all cylinder misfires) in the memory. I think this is all old data still stored in the memory, (a problem I fixed with a tune-up in late spring) and something I read in the owner’s reference guide suggests that if the light is off all the time it indicates that the problems are no longer detected, but there are codes stored. Does anyone know about this?
The MIL light should come 'on when the ignition key is turned to the run position but the engine not started i.e. not running. Once the engine starts the light should go ‘off’ shortly.
If the light is not coming on, it could be a bad bulb, a open fuse feeding that circuit, open wiring from the fuse to the bulb, open wiring from the bulb to the PCM, or a defective driver in the PCM, i.e. bad PCM.
Hope this helps.
It might be a good idea to have those codes reset. If they come back, it means there is something that should be addressed. If not, then great.