PCM (power control module) doesn't control Radiator Fan!

OK, the fan runs if the relay is jumped, and the relay tests fine, and the temperature sensor is fine.

But the Power control Module (PCM) is not turning the fan on when the temperture get high enough, nor if the Air Conditioning is on.

1993 Chevy Corsica, 6 cylinder.

One wire goes to fuse #9 (20) and is hot when ignition is on or in “bulb-test”… I need to see that it is hot; an easy check.

The other goes to the PCM behind the glove box. I need to see if the wire is connected. The PCM is supposed to ground this wire.

For $79 I can buy a replacement PCM, or for $89 I can have someone do a “diagnostics” to tell me if I should replace the PCM.

Would you replace the PCM after checking the two wires? Is any programming required?

(20) --> (20 amp fuse)


Both control wires to the relay are fine. Pink with black stripe measures 12 volts to ground when the ignition is on. Green with white strip has good continuity to the connector at the PCM behind the glove box. (Actually to the right of the glovebox in the sidewall).

BUT, the part the store showed me is NOT the PCM; I went back to the store; it turns out what they showed me was an ignition module. They tried to look up the PCM, but they can’t as they don’t stock it and have no way to order it.

A friend is checking with the dealer. I’ll check two other part stores.

I still don’t know about the programing issues. Inside the metal box, it looks like a plug in microprocessor and EPROM; but I’m not sure.