Code 42

[Rock Doc]

Anyone have any experience with code 42?

Thanks, Rock Dock

 

[Ken]

Check the wires between the HEI module and the EST; check for a bad connection at the ignition module; check for a bad HEI module.

When the system is running on the Ignition Module, that is, no voltage on the bypass line, the Ignition Module grounds the EST signal. The ECM expects to see no voltage on the EST line during this condition. If it sees a voltage, it sets Code 42 and will not go into the EST mode.

When the rpm for EST is reached (about 400 rpm) and bypass voltage applied, the EST should no longer be grounded in the Ignition Module so the EST voltage should be varying.

If the bypass line is open or grounded, the Ignition Module will not switch to EST mode, so the EST voltage will be low and Code 42 will be set.

If the EST line is grounded, the Ignition Module will switch to EST , but because the line is grounded there will be no EST signal. A Code 42 will be set.

Also, a MemCal not fully seated in the ECM can result in a Code 42.

 

[Vettefan87]

I had code 36, and code 42, and the shop figured out it was the sensor, I think??? that is right on top of the foily thing....... on the passenger side. Sorry for the vague description I cant think tonight. Well suposedly this would stay in closed loop when it warmed up and it would set off the codes. Hope this may help


Justin