[shorod]

The PCM supplies the ground signal for the cooling fan relays through BJT transistors (PCM pins 28 and 46 it appears from the diagram above). You should be able to perform your checks from the sockets for the relays. Pull the relays and measure the voltage between the relay coil with respect to known ground. Turn the key to "Run" to energize the PCM relay. This should provide battery power to one side of the relay coil at the socket. Now check for battery voltage at the input to the switched side of the relay which is provided from the 40A F109 fuse. You should also be able to verify continuity from the output of the switched side of the relays to the connector at the fan motors. On the low fan wiring, you may have to set your meter to measure resistance to compensate for the fan motor resistor.

If all of these check out, then measure the battery voltage across the relay coil terminals at the relay socket with the A/C turned on. If you do not have battery voltage across either of the relay coil terminals, then you need to verify that the signal into the PCM is appropriate. That determination will come from measuring the resistance or voltage at the A/C switch input to the PCM and the coolant temperature sensor to the PCM. I'm on business travel so I don't have the PCM pinout available to me at this point.

If the inputs to the PCM are correct, indicating the PCM should be providing a ground to the relay, and the PCM is not providing that ground, the PCM is probably the culprit. You'd of course want to verify that there is continuity between the relay socket and the PCM connector at this point.

If all signals to the relay are correct, then the problem would appear to be with the relay, the fan motors, or a high resistance in the supply wiring which limits the current available to the motors, preventing the fan motors from starting up and running.

-Rod