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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 117 (Engine Control System & Fuel - 4.8L, 5.3L, 6.0L And 6.2L - Diagnosis & Troubleshooting) >> Cylinder Deactivation (Active Fuel Management) System Diagnosis >> Circuit/System Verification

Circuit/System Verification

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  1. If any DTCs are set, then repair those DTC first. Refer to Diagnostic System Check - Vehicle .
  2. Start and idle the engine.
  3. Allow the engine to reach normal engine operating temperature. The engine should idle smoothly without any misfires. If the engine misfires, refer to DTC P0300 - P0308 .
  4. Monitor the cylinder deactivation system data parameters with a scan tool.
  5. Road test the vehicle under light throttle and load conditions that will allow the ECM to command V4 mode. If all enabling conditions are met for cylinder deactivation, and if no internal engine hydraulic/mechanical fault conditions are present, the ECM will continue operation in V4 mode.
    • If the vehicle passes the Circuit/System Verification test, then review the active fuel management driving information in the Features and Controls section of the owners manual with the vehicle operator, or instruct the vehicle operator in the proper driving techniques to obtain V4 mode.
    • If the vehicle does not pass the Circuit/System Verification test, then review the cylinder deactivation inhibit reasons listed on the scan tool.
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