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Diagnostic Trouble Code: B0018
Diagnostic Trouble Code Name: Left Roof Rail Deployment Loop Stage 2
Vehicle Make: Chevrolet
Vehicle Model: Cruze (J300)
Diagnostic Code Entered By: ZerOne
Diagnostic Code Entered On: Wed Oct 06, 2010 11:00 pm
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Please Note: The DTC Information provided has been randomly generated.
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Diagnostic Trouble Code Description:
Cooling Fan Relay 2 Control Circuit High Voltage
Possible Sensor Faults
ECM
Possible Related Diagnostic Trouble Codes
DTC P0691-P0694
Circuit / System Description
The engine control module (ECM) commands the fan ON in either high speed, medium speed, or low speed, depending on cooling requirements. In low speed, the fan is turned ON at a reduced speed. In medium speed, the fan is turned ON at a higher reduced speed. In high speed, the fan is turned ON at full speed. In low speed operation, the ECM provides ground to ECM terminal 51 (X1). The cooling fan relay activates and provides ground to the coils of the cooling fan medium speed 2 relay and the cooling fan speed control relay. The cooling fan speed control relay activates and provides power to the coil of the cooling fan high speed relay. The cooling fan high speed relay remains inactive because ECM terminal 71 (X2) is not grounded. The cooling fan medium speed 2 relay provides power to the engine cooling fan motor through cooling fan terminal?3 and the internal fan resistor. In medium speed operation, the ECM provides ground to ECM terminal 71 (X2). The cooling fan high speed relay remains inactive because power is not provided to the coil from the cooling fan speed control relay. The cooling fan medium speed 1 relay activates and provides power to the engine cooling fan motor through cooling fan terminal 2 and the internal fan resistor. In high speed operation, the ECM provides ground to ECM terminals 51 (X1) and 71 (X2). As previously described, power is now provided to both cooling fan terminals 2 and 3. In addition, power and ground are now provided to the coil of the cooling fan high speed relay. The cooling fan high speed relay activates and provides power to the engine cooling fan motor through cooling fan terminal 4, bypassing the resistors.
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