1994 Corvette 6spd

Have trouble starting the car. Sometimes will start up and then run fine. Other times will not start.

Code H42 came up.

What sould I replace. Please do not say opti.

Thanks

 

no. that is NOT an opti code...

I think this means something is amiss with your knock sensor... it is a knocksensor code for 92/93, and I think 94 and 95... but I don't rightfully remember for sure.

You really need the Helm Factory Service Manual so as to better diagnose this problem.

 

I got this from http://www.corvettephotographs.com/c4vettes/ecm.htm

42 Electronic Spark Timing Circuit (EST)

42 Check wiring at ignition module. Replace ignition module. Possible ECM failure.

I already replaced both the ignition module and the ignition coil. So I do not know what else to do.

 

that link is suspect. It does not include anything to do with the opti.

 

With Code 42, what we have here is a failure to communicate. The ignition module and the computer are in constant communication when the engine is in operation. (over 400 RPM) with the computer telling the module the correct timing.

If communication is lost or a circuit becomes infected with false signals (bad grounds, short to battery +, Electro Magnetic Interference {spark plug wires too close to circuit wiring}, oil contamination of the circuit connectors and wiring) then the computer will turn timing control back to the ignition module and flag the code.

Possible causes:

· EST circuit open or grounded.
· Bypass circuit open or grounded.
· Reference Ground circuit open or shorted to battery +.
· A bad computer to engine circuit ground.
· A defective ignition module.
· A defective computer.

If you are testing a vehicle for this code check the routing of the spark plug wires making sure they are not to close to the EST circuit(s) wiring.

Check the connector terminals making sure they are not over-sized or oil contaminated. Check the entire wiring of the circuits for chaffing,
short(s) ground.

Alldata has a very good on-line manual system for the DIY’s that contains all the information and a trouble “tree” chart(s) for the proper method to test the ignition module and computer for your vehicle.

http://www.alldata.com/products/diy/index.html