My CEL came on again today on the way to work, so I pulled into service, and although we have an OBD-II computer system here, we didn't have the little plug in card for Mazdas. (Which makes sense since we're a GM dealer. ) Anyways, I parked, and went in for my shift, having already booked an appointment for after school at my Mazda dealer. On the way home the light stayed illuminated.

Like I said, I'm taking it in tomorrow, but last time I threw a CEL, on the way to the dealer (no joke) about 5 mins away the light decided to turn itself off, and the service tech said that the code wouldn't even be stored once the light had gone off, and that they couldn't do anything unless the light was on.

I'm almost positive it's an O2 sensor problem (I have surging idle, etc) but they won't do anything unless the code is stored and the CEL is on!

So, (Edwin espesially) it was my understanding that an OBD-II computer will save all codes until they are reset. Why then did my light turn off last time? I hope it stays on right till the dealer this time, but Murphy's law says otherwise. Are they giving me a line about it not being stored, even if the light turns off?

 

Ok, so I'm at school now, with the light on all the way in this morning, and I just went out to grab my jacket, and I decided to start the car, just for curiosity's sake. Guess what? My light is OFF!!! I'm still going to the dealer after school, but I know they're just gonna tell me that they can't do anything unless the light is on, but whatever. This is really pissing me off! Like I asked before, once a code is registered, does it erase itself once it is ok, or does it remain in the computer until reset? Last time they gave me a line of "there won't be anything in the computer if the light is off." Bullshit, or true?

 

Hey Nick,
Found some info that may prove helpful:

http://obdii.com/background.html

In particular,

"Tell me about that "Check Engine Light".

The service industry calls the Check Engine light on your dash an "MIL" or Malfunction Indicator Light. It shows three different types of signals. Occasional flashes show momentary malfunctions. It stays on if the problem is of a more serious nature, affecting the emissions output or safety of the vehicle. A constantly flashing MIL is a sign of a major problem which can cause serious damage if the engine is not stopped immediately. In all cases a "freeze frame" of all sensor readings at the time is recorded in the central computer of the vehicle.

Hard failure signals caused by serious problems will cause the MIL to stay on any time the car is running until the problem is repaired and the MIL reset. Intermittent failures cause the MIL to light momentarily and they often go out before the problem is located. The freeze frame of the car's condition captured in the computer at the time of the malfunction can be very valuable in diagnosing these intermittent problems. However, in some cases if the car completes three driving cycles without a re-occurrence of the problem, the freeze frame will be erased.

Hope that helps.

 

****... The third time I start the car will be on the way to the dealer, but I'll hope the code stays in there.

Thanks for the help Mike!

 

That used to happen to me all the time It pissed me off how it would turn off right like 5mins before I get to the dealership.

The dealership told me that everytime it went on and off, it was stored in the computer.
But they fixed it now, so I'm A ok.