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Home >> Cadillac >> 2006 >> DTS 4.6 9 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 4.6L - DTC P0016 To P0401 >> DTC P0068 or P0121 >> Circuit/System Testing
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Circuit/System Testing

  1. With the 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.
  2. With the engine running, inspect for the following conditions:
    • Vacuum hoses for splits, leaks, and proper connections as shown on Vehicle Emission Control Information label
    • Air leaks at throttle body mounting area and intake manifold sealing surfaces
  3. Allow the engine to reach operating temperature. Observe the Manifold Absolute Pressure (MAP) Sensor Voltage parameter with a scan tool. The voltage should be between 0.8-4 volts.
    • If more than 4 volts or less than 0.8 volt, refer to DTC P0106 .
  4. Idle the engine. Observe the MAP Sensor kPa parameter with a scan tool. Increase the engine speed slowly to 3,000 RPM, then return the engine speed to a stabilized idle. The MAP sensor kPa parameter should change smoothly as the engine speed is increased and returned to idle.
    • If the MAP sensor kPa parameter does not change, refer to DTC P0106 .
  5. Take a snapshot of the engine data list while performing the actions listed below. The MAF sensor parameter should change smoothly as the engine speed is increased and returned to an idle.
  6. Idle the engine.
  7. Increase the engine speed slowly to 3,000 RPM, then return to an idle.
  8. Observe the Mass Air Flow (MAF) Sensor parameter frame by frame with a scan tool. The MAF sensor parameter should change smoothly as the engine speed is increased and is returned to idle.
    • If the MAF sensor parameter does not change smoothly as the engine speed is increased and is returned to idle, refer to DTC P0101 or P1101 .
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