Well I just put a rebuilt engine in my 95 z28. It runs really great considering I am still being gentle during break in. Upon start-up the SES light was on but it sounded great so I broke the cam in. Half way through break in of the cam the light went off. Well next day I started it up and the light was back on. I scanned for codes and this is the only one that came up. It then cleared its self once the engine reached about 180*. So I checked the grounds near the coil and the starter, both were good. I really dont know what else to look for.

I have now put 150miles on it and the light still comes on and goes away once reaching operating temp. I know my battery is also not holding a charge and tested bad so I will replace that tommmorow.

any help is greatly appreciated, will

 

Your asessment of the code has to be incorrect. The 42 will not turn on the SES light and it will disable the engine. You may have had a 42 previously and saw it when you scanned it but it has since gone away obviously since your engine is running. It also was not the reason the SES light came on. There must be another code present that is turning on the SES.

Scan it again thouroughly and reset all codes then look for those that return.