1999 Oldsmobile Cutlass

Engine Cooling problem
1999 Oldsmobile Cutlass 6 cyl Front Wheel Drive Automatic 135000 miles

the fan does not kick on when it suppose to at all. The only way it will turn on is when I unplug the thermostat sensor.
i replace all the relays and the thermostat sensor and tested the fan motors.
what should I do?
Richard findley
April 23, 2010.

Check the PCM. The temp sensor sends a signal to it and then it goes to the relay and to the fan. Also, make sure there are no damaged wires.

Let me know what you find.