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GMC
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2006
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Envoy 4.2 S, RWD
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Repair and Diagnosis
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Engine Performance
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System
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Engine Control System - 4.2L - DTC P0420 To P1682
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DTC P0420
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Circuit/System Verification
Circuit/System Verification
Operate the vehicle within the Conditions for Running the DTC.
If the DTC fails this key cycle, proceed with Circuit/System Testing.