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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 370 (Engine Controls And Fuel - Hybrid (LZ1) - DTC P0010 Through DTC P0341) >> Diagnostic Information and Procedures >> DTC P0068 or P0121 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2011 GMC Yukon, 2011 Chevrolet Tahoe, and 2011 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
  1. Inspect for the following conditions:
    • Vacuum hoses for splits, kinks, and proper connections as shown on Vehicle Emission Control Information label
    • Inspect thoroughly for any type of leak or restriction
    • Air leaks at throttle body mounting area and intake manifold sealing surfaces
    • Throttle body for dirt, debris, and coking-Refer to Throttle Body Cleaning .
  2. Ignition ON, engine OFF, observe the MAP Sensor Voltage parameter with a scan tool. Voltage should be more than 0.8 volt and less than 4.85 volts.
    • If more than 4 volts or less than 0.8 volt, refer to DTC P0106 .
  3. Start and idle the engine. Observe the MAP Sensor kPa parameter with a scan tool. Increase the engine speed slowly and then back to idle. The MAP sensor kPa should change smoothly and gradually as engine speed is increased and returned to idle.
    • If the MAP sensor kPa does not change, refer to DTC P0106 .
  4. Take a snapshot of the engine data list while performing the actions listed below. The mass air flow (MAF) sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
    • Idle the engine.
    • Increase the engine speed slowly to 3, 000 RPM, then back to idle.
    • Exit from the snapshot and review the data.
    • Observe the Mass Air Flow (MAF) Sensor parameter frame by frame with a scan tool. The MAF sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
      • If the MAF sensor g/s does not change smoothly and gradually as the engine speed is increased and is returned to idle, refer to DTC P0101 or P1101 .
  5. Inspect the throttle body for the following conditions:
    • Loose or damaged throttle blade
    • Broken throttle shaft
    • Any throttle body damage
    • If any of these conditions exist, replace the throttle body assembly.
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