Operation CHARM
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GMC Truck
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1988
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R 3500 P/U 2WD V8-454 7.4L VIN N TBI
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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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Knock Signal
Knock Signal
Indicates
knock sensor
input to ECM. Display is "yes" when knock is detected and "no" when no signal received.