Check engine light comes on but no codes???

[TERRA Operative]

I've just recently finished rebuilding a Sera from the ground up, including the 5E-FHE engine. (basically the same as a 5E-FE from a Paseo, and the 4E-FE from the Starlet)

All is going well, except for the ECU keeps throwing a check engine light.
It happens every time the car almost reaches 2000RPM, but when the car is turned of and back on again, the code is cleared.
I've tried pulling the code without turning the engine off, but no dice. I know the system works as I had codes thrown earlier that were saved to memory and I was able to read them as per normal.
The car seems to run fine, but I want to get rid of this light. I've checked everything I can think of, can anyone shed some light on what else I can try?

[pandaah]

this might sound silly but try pulling the code, with diagnostic pins crossed and revving the motor to 2000rpm and holding while code flashes..

had to do this to my z20 to diagnose a dizzy fault

[George]

I haven't ever dealt with the exact engine model, but to my experience there are at least 2 possible reasons for the warning light to turn on at ~2000RPM:

1. Knock sensor(s) malfunction
2. AFR sensor heater "sense" terminal (if exists) not connected to the ECU. So the ECU thinks that heater circuit is damaged.

[TERRA Operative]

Thanks for the ideas, I'll check it out and see what I find.

[cambelt]

No sp1 input from dash to ecu .
Dave

[TERRA Operative]

mmmm, I'll be able to check that one too. I'll be pulling the dash out in the next few days to install tweeters so I'll check the wiring then.

[BLK_20v]

+1 on bridging it whilst the engine is running.... Put some male connectors on a small loop of wire which fit in snuggly.

[TERRA Operative]

I've pulled the dash out for the stereo install, so I'll check all the wiring to the ECU.
Once it's all back together, I'll have a go at reading the code again if (when) it reappears.