Quote Originally Posted by gmbooth View Post
This is what I'm checking for, is the signal directly to/from ECM to Cooling Fan Module or ECM (Fuse/Relay/Sensor) then Cooling Fan Module?
The ECM produces a PWM signal which requires an oscilloscope to read it correctly but you can at least check that there is a voltage on the signal wire to eliminate the possibility of a break or short. If I remember correctly it's a purple wire. Insert a single copper strand from a multi-strand wire into the fan connector on the purple wire and check the voltage between the wire and ground. The voltmeter will give you an average of the PWM signal voltage which should be somewhere between 1.2V and 10V. If there's no voltage then check the output at the ECM to make sure it's not a wiring fault.