GAm 2000 radiator Fan does not turn On

Can some one help me out ?
My Grand Am 2000 3.4L Fan radiator only turn on when AC is on. Fan does not turn on when temperature value is reached. Relays are O.K Temp Sensor is O.K. It looks something releated to the ECM but not sure.
Tepas.

Welcome to AF.

The PCM commands Low Speed Fans ON under the following conditions:

The engine coolant temperature exceeds approximately 106°C (223°F).
The A/C refrigerant pressure exceeds 1310 kPa (190 psi).
The vehicle is shut off when the engine coolant temperature is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay ON for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:

The engine coolant temperature reaches 110°C (230°F).
The A/C refrigerant pressure exceeds 1655 kPa (240 psi).
When certain DTCs set.

Also check this thread....
http://www.automotiveforums.com/vbulletin/showthread.php?t=691256

btw if it is the PCM that's bad then a dealr would have to diagnose this.

Thanks xeroinfinity.
Is the ECT sensor the one mounted near the thermostat ?
I disconnected with the key on and saw the Temp gauge went down so I figured that sensor just control the temp gauge.
Thanks.

That would be the ECT sensor near the thermo housing, located on the intake by the TB.

If its bad the fans usually wont turn on.

Also by disconecting that and turning on the car it will throw a code :grinyes:

Here is a test procedures for that ECT sensor (http://www.automotiveforums.com/vbulletin/showthread.php?t=660655).
That will tell you if its the sensor or the PCM.

Thanks xeroinfinity.
I changed the ECT sensor but the Fan still don't work. I checked the harness and I got 4.9V from the ECM. If the temp gauge is working it means that the ECM is receiving the sensing signal from the ECT but somehow the ECM MICRO is just driving the temp gauge but not the fan relay. I will take it to the dealer for ECM diagnostic.

That voltage is within limits.
Did you check the resistance though ?

and again unless you car gets up to 225-230 deg it wont turn the fans on.
If you cycle the AC it should run both, so that tell me thiers nothing wrong.

you can also check the fuses under the hood i had the same probnlem and i had a blowed fuse

Thanks spanky, fuses and relays are working O.K

Thanks seroinfinity,
Both fan turn on when AC is on, that's not the problem.
Both fan do not turn on when 225-230 or more deg are reached. So more likely I have a problem with the ECM.

It could be the PCM or it could be the wiring.
You did look over them and especially the wires right where the plug in is?

Sometimes the wires get fraid then you get a resistance drop, which could cause the fan not to run.

Btw how did you test the relays?

thier are several fuses/relays under the hood too.
#8 maxi fuse , #12, #14 & #15 mini relays and I think #52 is a fuse.