The fan are controlled by the engine computer based on input from the coolant temperature sensor.
unplug the Coolant temperature sensor and see,if the other fan comes on.There are three wires from the Engine Coolant Temperature sensor or CTS for short (Coolant Temperature Sensor). One wire gives the temperature signal to your dash temp gauge, one gives a temperature signal to the PCM, and the other provides a low reference signal to the PCM and provides the signal to turn on the fans.If the CTS wire is short then it will not signal both or any one fan to come ON.---------- To check Coolant Temperature sensor wiring.Click this link below:--
http://i266.photobucket.com/albums/ii259/SyntheticShield/Grand%20Prix%20Diagrams/Electrical%20Diagrams/Coolant_Temp_Sensor_Connector.gif
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Also you check the fan connections and wiring too,this will help to locate the exact short in wiring:---
To get the exact wiring.Please click on the link below:----
http://i266.photobucket.com/albums/ii259/SyntheticShield/Grand%20Prix%20Diagrams/Electrical%20Diagrams/Cooling_System_Schematic.gif
You can see in the last diagram that the fan relays go directly to the PCM to get the ground (or low reference) signal in order to engage and that comes directly from the CTS.You can see in the last diagram that the fan relays go directly to the PCM to get the ground (or low reference) signal in order to engage and that comes directly from the CTS.You can see in the last diagram that the fan relays go directly to the PCM to get the ground (or low reference) signal in order to engage and that comes directly from the CTS.
You can see in the diagram that the fan relays go directly to the PCM to get the ground (or low reference) signal in order to engage and that comes directly from the CTS.
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This should help.Thanks.Helpmech.
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