Hello everyone. My CEL came on while driving to work today. Talked with the guys at MRT and they will take a look tomorrow morning. Not wanting to wait until then, I plugged in my Predator to see what the trouble code was and it showed nothing. Any idea why that is? Do some things fix themselves? I always thought that if there is an trouble code of some sort it will show in the tuner until it is cleared either by me or the guys that work on my car. Your input is greatly appreciated.

Jon

 

I once had a CEL show up while driving. By the time I got home it was off again. I checked the codes with my predator and there were none. I scratched my head a few times and it never happened again. Although another time I got the airbag light, and that too went away after 5 mins of driving.

 

Glad to hear I'm not the only one. I suppose if it was a major concern the Predator would be showing the code.

 

I don't remember the specifics, but I believe that the car must experience the fault for 3 consecutive drive cycles before a error code is generated that the Predator can read. I had the CEL light once and my Pred didn't identify anything either. I reset it and it never happened again.

 

Most codes need to be activated multiple times before the CEL comes on, but the computer has them stored and ready to output them, even if they haven't tripped the CEL yet. Some OBD-II readers will read codes that have not been thrown yet. The reader I have lists them as 'Pending'. If you know someone with strictly a reader, you might try hooking that up, to see if you can get the information.

 

Whats the logic behind this? Why does a code have to be tripped multiple times before the CEL comes on? To minimize false positives? But why would a code trip if there was nothing wrong? More importantly why would you need to use your predator or another kind of reader to check a code that is pending? Does that signify a problem that is festering? Sorry for the million questions, but this discovery just blew my mind.

One more thing, one time when reattaching my CAI I didnt do a good job tighting it to the TB. Within a second of starting the car up I got a CEL. Did that "too lean" code trip multiple times too? or do some important error codes trip the CEL from the first time?

 

You are exactly right about why some codes need to be tripped for multiple drive cycles. If there's a momentary fault, the computer doesn't immediately report it, as it might clear up. Engines are fickle things, and they always fluctuate just a bit when running.

Some codes are simply too important, and the first time the code reads, it throws a CEL. The 'too lean' code would be one of those, I'd have to imagine. Basically, if it can cause serious damage quickly, it'll throw the CEL immediately... If it's less serious, the computer double checks its work.