Had a CEL a couple of weeks ago and reset the ECU by pulling the fuse, my reasoning being if it comes back then I'll investigate further, if not I'll put it down to a spurious incident.

CEL light came back again on Saturday in similar circumsatnces to the first time so I left it as is and have oredred a code reader that should arrive in the next day or so.

Funny thing is, I get in the car this morning and the light has gone off. I haven't pulled the fuse or disconnected the battery. This seems more than a bit bizarre to me as I understood that the light would stay on until it was reset.

The only think I can possibly think of is that it was the first frost of the year this morning and maybe cold had some effect on it, but I know this is a long shot.

So can anybody shed any light on whether the light stays on ad infinitum or whether it self clears when

a) The problem goes away or
b) After a set period of time.

Thanks.

 

Depends on the error. If you disconnect the knock sensor, light will stay on until you fix the issue. Code stored.

I've had a CEL regarding ABS (after 2 dyno days, front wheels stationary, rear wheels moving). Light cleared itself after 4/5 engine re-starts. Code stored.

Map sensor issue. Only came on when engine was struggling (after warm and a few miles), cleaned sensor, light out, no code stored.

 

If the problem goes away then sometimes the CEL will go.
It all depends on what the problem is.

 

Thanks for that.

Guess I'll have to wait for the code reader to arrive to get a better idea of what's been happening.

 

Oh, and I had an O2 primary pre heater CEL too. That would come on within 30 secs of starting the car. But as soon as I fixed the issue, the CEL went out on the next re-start. No code stored.

(all error codes obtained via the 'import' paperclip method)

 

My general misfire codes (injectors in the end) would clear themselves once switched off. The time I spun on track and got a CEL (probably turned the engine slightly backwards) I had to pull the fuse.

Paperclip.

 

LTB - did you get a code out of it in the end?

 

Not yet Mikey, still waiting for the OBD II reader to arrive.