car: 1993 chevy cavalier vl

error code 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module.

also with the key in run position it normally lights up the check engine light to let you know its on but now in run it does absolutly nothing and with the key in accessory all that stuff works

so i went to autozone and had the startern, coils, and the ignition control module tested and they are fine. the battery is also fine

also from what i have heard is that the ecm can also throw a code 42 and other right before it goes bad

so what do you think?

Below is a copy and paste dealing with code 42, may or may not shed some light, goodluck !

The circuits and their functions:
� Reference.
This circuit provides the computer with RPM information. If this circuit becomes open or shorted to ground the engine will not run, because the computer will not operate �trigger� the fuel injectors.

A common saying here is, no reference no run.


� Reference ground.

This circuit is grounded in the ignition module and the computer; it makes sure the ground circuit has no voltage drop, which could affect vehicle performance. I have found an open in this circuit can cause a vehicle �no start� as well as a false code 42/E23.


� By-pass.
The computer applies 5 volts to this circuit to switch timing control from the ignition module to the computer. The computer is telling the ignition module that it will control the timing. An open or a short to ground of this circuit will set the code and the engine will run on base timing. (Plus a small amount of advance built into the ignition module.)


� EST.
This circuit triggers the ignition module. The computer does not know what the actual timing is, what it does know is when it gets a reference signal. It uses this reference signal as a base point and advances or retards the spark from that point. So, if on vehicles where the base timing is adjustable, and the base timing is set incorrectly, the spark curve will be off through its entire range by the amount that the base timing is misadjusted. An open or short to ground in this circuit will set the code and cause the engine to run on ignition module timing.
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.

so far all that looks good but the thing that is baffling me is that all the interior electrics (stereo, lights, ect) work with the key turned to acessory but with the key in run i get no dash warning lights and none of the engine electrics work like fuel pump, guages. and now the paper clip trick doesnt even work. so my thinking is it is either the computer or the ignition switch could be malfunctioning in the run position

Sounds like you are on the right track.
My guess is a bad ignition switch.

ok so the problem was a shorted out wire that also took out the ignition switch computer

so about 100 bucks for the switch and the computer and it now runs lets just hope it stays that way