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Home >> Hummer >> 2009 >> H3 Base, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls And Fuel - 3.7L - DTC P0013 To DTC P0315 >> DTC P0068 or P0121 >> Circuit/System Testing
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Circuit/System Testing

  1. Inspect for the following conditions:
    • Vacuum hoses for splits, kinks, and proper connections
    • Inspect thoroughly for any type of leak or restriction
    • Air leaks at throttle body mounting area and intake manifold sealing surfaces
  2. Allow the engine to reach operating temperature. Observe the Manifold Absolute Pressure (MAP) Sensor Voltage parameter with a scan tool. Voltage should be more than 0.8 volt and less than 4 volts.
    • If more than 4 volts or less than 0.8 volt, refer to DTC P0106 .
  3. 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 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 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 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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