I've spent (off and on) several weeks trying to figure this out.

In a nutshell, my cooling fans do not turn on.

The PCM is seeing the correct temperature as witnessed by a scan tool. I've tested the relays - all fine. The fuse is fine, both in the engine compartment (Fan) and the HVAC fuse in the cabin.

I verified that the fans do work by jumping the relays to activate the low speed fans.

What I do know: I'm not seeing the 5vdc trigger voltage from the PCM on one of the two leads. There are two inputs: one supplies the trigger to relay #1 for low speed. This one is not showing power. The other supplies the trigger to relay #2 and #3 it shows 5vdc.

I forced the PCM into field service mode (which activates the fans) by jumping pin #5 and #6 under the dash. I tried to activate the fans by turning on the a/c, but no luck.

My question: Is it possible that the PCM is bad? Everything else sems fine...starts, runs, no DTC, etc.

I used my scanner and all seems fine.

Is there a way to test the PCM? Is it repairable?

 

As noted in the reply on F-Body.com:

-did you check the fusible link?

-the PCM supplies a ground to activate the relay, not a +5V signal.