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Home >> Cadillac >> 2009 >> STS V >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 4.4L - DTC P0010 To DTC P0158 >> DTC P0068 or P0121 >> Circuit/System Testing
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Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with the Circuit/System Testing.
  1. Inspect for the following conditions:
    • If any of the above conditions are found, repair as necessary.
  2. Allow the engine to reach operating temperature. Observe the MAP Sensor Voltage parameter with a scan tool. Voltage should be greater than 0.8 volt and less than 4 volts.
    • If greater 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 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 airflow (MAF) sensor g/s should change smoothly and gradually as the engine is increased and returned to idle.
    1. Idle the engine.
    2. Increase the engine speed slowly to 3,000 RPM, then back to idle.
    3. Exit from the snapshot and review the data.
    4. 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. Ignition ON, slowly depress the accelerator pedal to a WOT position, then slowly release the pedal while comparing the TP Sensor 1 and TP Sensor 2 parameters. The difference between the parameters should be less than 4 percent.
    6. WARNING: Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury.
  6. Ignition OFF, 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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