The dreaded CEL again

[MRichards]

I have a Y2000 3200GT with SD2 diagnostics which is throwing up a CEL. The CEL is not affecting the performance,it's just a nuisance. Both my Unidiag software & a Leonardo tool show no DTC's. On startup there is no CEL for about a minute at idle. A quick blip on the throttle erases the CEL,but it reappears permanently at idle a short time later. A hot restart gives no CEL. The car is stock standard apart from a new Marelli throttle body & the electronic pedal pot.
The car has been thoroughly checked over by a competent mechanic & no faults found during three weeks.

Does anyone on here know why this CEL appears ? Grateful for any expert advice & wild guesses.

 

[mowlas]

A few wild guesses would be:

1. Inefficient/degraded CATs
2. Faulty or dirty O2 sensors
3. Faulty or intermittent crankshaft position sensor

Although (without knowing the diagnostics of the 3200 GT), not sure why these would not throw readable error codes.

 

[MRichards]

New O2 sensors fitted recently,so unlikely a problem.

 

[davy83]

I would be a little concerned as to why you have no DTC's but do have an ECU error light? That in itself is a little odd. Stuff that creates errors (normally with a code) but does not affect the engine running too much are - Knock sensors (very common), O2 sensors are previously mentioned, possibly the CAM sensor, which is secondary to the crank sensor in terms of importance.
I had an issue with the crank sensor, which has been suggested, which did throw an error which immediately cleared and this took a while to become a fixed error so that's possible.
CATS might be an issue but I think that would create an O2 sensor problem?
Not sure if any of this helps.
It also might just need driven? Been for a decent run recently?

 

[Maser Sod]

When I had my 3200GT I learned to live with the CEL light - it would go on and off on a very regular basis. It was the one black mark on an otherwise enjoyable period of ownership. The reasons already mentioned above are the usual suspects, however it's worth adding that the throttle potentiometer is another culprit. Or at least that's what I remember from back in the day when I had mine (20 years ago now). Obviously, without a code being thrown you are in the realm of guesswork, but I thought I would mention it nonetheless.