I have a '91 Camaro Z-28 that is throwing the 43 code...Engine acceleration lagging. Knock sensor & pigtail wire harness are new...as is the distributor, ICM, coil, alternator & battery. Is replacing the ESC an option or is that within the ECM for 1991? If so, can it still be tested or think the ECM is only logical next step? Could knock wire proximity to spark plug wire or other trigger code 43? Thanks for the help!

Thanks for the info and sorry for the delayed response. I put in a brand new KS and same problem occurred (SEL: code 43). The pigtail wire put out 5v., but the KS had 0 ohms of resisitence, so it was actually defective! I purchased a second brand new KS and that yielded 3.9k ohms...problem solved! I will keep your contact info on hand should an ECM be needed in future...Z is 28 years old, so may be sooner than later! Ha!