I've got an '87 trans am with a 305 and a four barrel. To make a long story short, I was getting a lot of error codes and the timming was way off, so I pulled off all the wiring to check and re did the timing and vacumm. Which narrowed all my problems down to one error code, code 43. Electronic Spark Control failure. I figured it was probaly a knock sensor, so I replaced the knock sensor and since then I have gotten two more error codes in addition to the code 43. I got 41 and 42 now. Cam sensor and Electronic Spark timing failure.

Now I'm not sure where to look. I'm guessing I either have a defective ECM or a defective ESP module. Does anyone know how I can test either one of these short of just replaceing them?

Thanks