[Guv Bob]

This not a lot of detailed info about these old 1G's out there, so I'm having to do a lot of guessing...

My problem is the Check Engine light does not illuminate. The bulb and all circuits external to the ECU board are fine. The board is also good between the 12VDC into the board from the bulb and ground. I suspect the trouble is the transistor, resistor or any associated capacitor, but the board has been worked on before and the markings on these parts are no longer readable.

Without a schematic, I wonder if someone more familiar with this type of circuit could guess at a possible replacement for the transistor and capacitor.

I know this is not the "proper" way to do it, but the alternative is buying a new ECU - several hundred $$. So I'd like to try a few things that might have a chance of working before doing that.

Here's the only schematic I can find that shows the transistor and resistor on the board, but no info as to what the parts are. Also, can't find what is connected to the base, and can't get in to check the base signal. I can swap out the parts from the component side of the board OK, but can't trace the leads without damaging something else on the board -- due to the condition of the board.

Probably sounds goofy to you guys, but until I can get that light to work and the car to pass smog, I can't justify spend much cash on restoring the car.

http://img823.imageshack.us/img823/7787/pdv.gif

Thanks in advance!

Bob