I've got a 94 with a 3.4 and the electric fan isn't working on its own. It does come on with A/C like it is supposed to but not with engine temp. I can command it on with my TechII and it has the proper power and grounds. Relay is good and the temp switch is good. When I try to bypass the switch by grounding the wire the fan still doesn't work anyone ever run into anything like this?

 

The fact that you can command the fan ON with the TchII indicates that everything is OK from the PCM to the fan, including the fan. The PCM looks at the input from the ECT sensor and ativates the fan as needed. The ECT sensor may be bad or changed value, or there is a wiring problem from the ECT to the PCM. There is no temp or fan switch on these cars. With the TechII you should be able to read the temp that the sender is sending to the PCM and decide if it makes sense or not. Disconnect the sensor wires, and turn engine ON. Looking back with a Voltmeter on the yellow wire from the PCM you shouls see 5 Volts to ground. Looking back on the Blk/Pnk wire toward the PCM you shouls see 0 Volts, and a short to ground. Shorting the two wire to each other simulates an overheating condition and should force the fans ON.

 

Dude, the 2-wire sensor is the one for the Temp. Guage 5-Volts going to it and the remainder headed towards the IPC (instrument panel cluster). It is operating as designed. The temp. reads correctly with the guage and the on the TechII. There is a temp. switch and it is located on the driver side head next to the power steering pump bracket. I did find the problem though, I had an alarm at Audio Express a couple of months ago you know the home of the $1.00 installation fee. And they tied in the sensitivity module into the 5-volt referece data line causing the PCM to think that the motor was pretty damn cold and not engaging the fan. Problem fixed. Thanks