If it has a temperature sender unit on the radiator you can test it to see if it's that which is causing the problem.
If it's a standard 2 wire plug on to the sender you just unplug it and quickly short the 2 wires in the plug together by inserting something like a paper clip. If the fan starts then you need a new sender unit. The sender it'self is only a switch that connects the 2 wires together when the correct temperature is reached. You may need to have the ignition on, but some fans continue after the engine is off and the key removed.
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A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
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After the vehicle is shut off if the engine coolant temperature at key-off 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 BCM and PCM/ECM command High Speed Fans on under the following conditions:
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Engine coolant temperature reaches 110?°C (230?°F).
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A/C refrigerant pressure exceeds 1 655 kPa (240 psi).
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When certain DTCs set.
The three relays are located in the under hood fuse / relay box ! You need to have it checked for DTC'S -diagnostic trouble codes ! An you need a GM Tech 2 scan tool !
This diagnostic procedure supports the following DTCs:
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DTC P0480 Cooling Fan 1 Relay Control Circuit
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DTC P0481 Cooling Fan 2 and 3 or S/P Relay Control Circuit
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DTC P0691 Cooling Fan 1 Relay Control Circuit Low Voltage
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DTC P0692 Cooling Fan 1 Relay Control Circuit High Voltage
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DTC P0693 Cooling Fan 2 and 3 or S/P Relay Control Circuit Low Voltage
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DTC P0694 Cooling Fan 2 and 3 or S/P Relay Control Circuit High Voltage
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When the A/C is requested and the ambient temperature is more than 50?°C (122?°F).
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A/C refrigerant pressure exceeds 1310 kPa (190 psi).
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After the vehicle is shut off if the engine coolant temperature at key-off 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:
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Engine coolant temperature reaches 110?°C (230?°F).
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A/C refrigerant pressure exceeds 1655 kPa (240 psi).
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When certain DTCs set.
So
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