I have a code 43 on my 91 z28 305 tpi. The code is for the ESC. I have replaced the ECU and knock sensor. I believe that the computer thinks it has a knock because when the clutch is engaging, it will retard the timing dramatically. The motor has 1100 miles on it and has ALL NEW sensors. I have replaced part after part eliminating things as I go. The only thing that I have left to do is either hook up a resistor in place of the knock sensor (which I think is supposed to be between 2200-3300 ohms??? ) or replace the mem-cal/PROM. If anyone knows where I can find a new mem-cal/PROM please let me know or if that is the correct resistance for the knock sensor. I will be getting a scan tool to give me live readings from the computer soon, just trying to get some homework done on what it will cost me on some things. Thanks

 

Chevy dealer should be able to oeder one for you, around $60.

 

Ok, so I got a scan tool off of ebay. The PROM ID is 5291. Does anyone have a scan tool that knows what the ID is supposed to be on a 305? or is there a way to look it up? the motor is sensing a slight knock. When the rpms are accelerating, the knock retard gets up to 20 degrees. The spark advance on the other hand is sitting at around 20 degrees at idle and then going up to around 40 when accelerating. The base timing is set at around 10 degrees. Any ideas as to what the hell is goin on?