code 42

driving down the road, and i notice my tach fluctuating, bouncing around everywhere. I thought it was weird, but no biggie. Then the tach does it again, and it dies. code 42 is brought up. Now everytime i start the car service engine light comes up, and its code 42. I had a bad fuse and replaced it, other than that I have no idea where to start. any help where to look would be great.

Electronic Spark Timing bypass circuit or EST circuit is grounded or open. A malfunctioning HEI module can cause this code. It would also explain the dead tach.

thanks man, after parking it for a few days I discovered it wouldn't start. Replaced the module, systems all go. Much appreciated.

you DID replace it with an AC Delco unit right? If not you'll be replacing it again.

you DID replace it with an AC Delco unit right? If not you'll be replacing it again.


...uh oh. i used bosch