I have read that there is a LED on the ECU itself that flashes, and not the check engine light, but I don't know how to trigger it.

I would assume that there is a check connector somewhere that needs a jumper, but I am not positive. This is for a 1991 Civic SI.

Thanks

 

There's an led window under the passenger side carpet.
Just roll it back, you'll see it. Put igintion to on, and count
the flashes.

 

One question on this, is there a flash when you turn the car on and off? I turn the engine on and I get one flash. Wait about 20 seconds and turn of the car. When I turn off the car I get one more flash. Is this normal or is it the O2 sensor?

Thanks.

 

Yes there is, perfectly normal.

 

One long blink counts as a 10. A short blink is 1. Add them together and you get your code.

 

The ECU will blink in a very obvious way. If the CEL is on and the ECU is not blinking a code, try resetting the ECU and go from there. OBD-0 ECU's have no jumper.