Well, the car (91 L03 700R4) failed emissions with twice the amount of allowable NOx. This seems logical, since I've got a Code 32 (among others but its the lowest) which is the EGR valve and it works to lower combustion chamber temps thereby decreasing ping, detonation and emission of NOx. So instead of spending $55 for a new EGR and $45 for a new EGR solenoid I figured I'd bite the bullet and diagnose it (reading over the diagnosis previously seemed pretty daunting, but it wasn't so bad, heh).

I went through the diagnosis, step by step, as detailed in the Haynes manual which works by eliminating first the valve, then the solenoid, then the ECM. The valve worked as it should, but the solenoid didn't.

I then went through the diagnosis that the GM Service Manual details which eliminates the ECM first, then the solenoid, and finally the valve. It immediately determined that the ECM wasn't sending any voltage to the solenoid when it should have been. I checked the wire (from the ECM to the solenoid) to ensure continuity and it was fine.

This leaves me with the Haynes manual telling me the solenoid is bad and the service manual saying the ECM is bad. The easiest and cheapest route would be to buy a new solenoid and diagnose the problem again, then go the route of swapping ECMs. Its quite feasible that both have gone bad as well.

Has anybody else gone through this similar diagnosis and what did you end up with? How feasible is it that I have a malfunctioning ECM? FYI, the other codes in the computer are 42 and 54. I started with the lower code first as the service manual advises. Any input is appreciated. Thanks.