Operation CHARM
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GMC Truck
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1989
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C 3500 Truck 2WD V8-305 5.0L
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Repair and Diagnosis
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Powertrain Management
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Computers and Control Systems
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Testing and Inspection
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Scan Tool Testing and Procedures
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Positions
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Fan
Fan
Monitors ECM command to engine cooling fan. Displays "yes" when ECM energizes fan relay. Indication should be "no" when coolant temperature is below 106°C.