The following troubleshooting chart resolves erratic performance and no codes displayed. For troubleshooting procedures, refer to the appropriate engine service manual.

Cannot get full power.

  • Plugged fuel filters.
  • Hose not connected to Turbo Boost Sensor.
  • Verify injector calibration(s) are correct.

Cannot get full throttle.
Mis-calibrated Throttle Position Sensor.

Runs rough; misses and occasionally stalls.

  • Improper gapping of Timing Reference and Synchronous
  • Reference Sensor.
  • Fuel leaks.
  • Loose battery power, ignition or ground wires. Injector failure.
  • Vehicle speed sensor failure.
  • Injector harness failure.
  • ECM calibration.

Engine idles high after warm-up or hangs.

  • Incorrect calibration of Throttle Position Sensor.
  • TPS linkage or pedal problem.
  • VSG signal wire shorted to voltage source.

Low road speed.

  • Determine road speed specifications for vehicle manufacturer data.
  • If road speed is less than specified and all mechanical checks are
  • correct, then cruise control calibration is suspected.

Vehicle surges or bucks.
VSS may be supplying incorrect data to the ECM.

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