I have a 91 GTA.
I am getting codes 42 and 43.

So far I have checked sensors to be working
oxygen sensor
MAP sensor

Some wierd problems I am having is:
-when I hook my laptop to the car it shows that the knock sensor is retarding 20 degrees, then I unhook the knock sensor and it still pulls 20 degrees out
-I pulled the plugs out, cylinders 1-4 are showing lean, 5-8 are showing rich.


So where is my ESC on a '91 GTA?

Could my problem be a ignition module?

BTW, the problem happened when I was racing and spraying nitrous too.
But I did run the car for a whole season with no codes.

Any help?

 

I am gonna try a new knock sensor tonight and see if that fixes it

 

don't forget to clear the codes by disconnecting the neg. battery cable for a min or so.

 

If the knock sensor is working properly, you might have a bad ESC Module. I just replaced mine and that seemed to fix my problem. If the ESC is ok, it could be the connector on the ECM (Most likely not)

If you have a lot of mods to your engine like a mild cam or headers, you could be getting false knock. I'd suggest throwing a 3.9k resistor in place of your knock sensor. I just have the wire hooked up straight to my negative on the battery.

 

Update!

The new knock sensor fixed the problem

 

Glad to hear it. Good thing it was an easy fix for you.