CEL code 42?

J

JohnnyPC1

New member
Well, I'm kind of stumped here. I have a code 42 that I can't get rid of. Seeing on a Google that 42 typically deals with ignition, that's where I've been looking for a culprit. So far I have replaced the plugs, cap rotor and HEI module. Wires look to be recently replaced so I skipped those.

I've also checked the connections at the ECU and it all looks to be OK. I mention that because I don't know if it was coincidence or not but I noticed the CEL shortly after pulling the ECU to try a used I bought for a backup. Both my original ECU and the "new" one throw the code...any other places to check? Which pins on the ECU deal with the ignition circuitry? Maybe something got squashed with all the in and out the ECU went through? I drive the truck everyday with this light on and I want it gone!!! Thanks!
 
jjorgensen52

jjorgensen52

NHSTE - I'm the only one!
Re: CEL code 42?

This link contains almost all of the wiring info for the ECM
http://www.syty.huryde.com/wp-content/uploads/2005/12/Wiring Diagram.pdf

You have datamaster you could run on the truck?

I turned this up on google
Why the computer flags this code.

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 to 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.

The ignition module (actually inside the distributor) has been known to cause problems in these trucks. I would try swapping that out. (I am going to feel stupid if by HEI module thats whaty you meant :roll: )
 
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