Hey Everyone, my latest "project" is a '90 Brougham I saved from the salvage yard. It has the 5.7 (350) Chevy FI engine @ 106k miles but it has developed a pesky problem with the "Knock Sensor" system (officially called Electronic Spark Control, or ESC). After driving the car approx 10 miles (more or less) the "Check Engine" lamp will come on and the Climate Control will tell me it has a code 43 ECM problem, which is something with the Knock Sensor system. When this happens, power is NOTICABLY less (you have to floor it to maintain 50MPH!). Sometimes the car will go back to normal on its own, but most of the time I have to shut it off and restart to get it to go away (temporarily).

I tried replacing the ESC module from a '91 Brougham with the 5.0 FI engine, but no luck. I also tried bypassing the entire system by sending +12v into the ECM on the line coming from the ESC, but it appears (according to the service manual) that the ECM performs a once-per-startup functional test of the ESC system, and if it fails, the code 43 will result as well, so bypassing the ESC doesn't work either. I haven't yet replaced the Knock Sensor itself, but before doing it I wonder if this is a common problem out there and maybe someone knows if something is causing the knock sensor to report all this knocking (vibration) to the ECM constantly causing the code 43.

Any guesses or suggestions would be appreciated!! Doug