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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 431 (Engine Mechanical - 6.5L (On-Vehicle)) >> Adjustments & Inspections >> Fuel Injection Pump TDC Offset Adjustment >> TDC Offset Clear & Relearn

TDC Offset Clear & Relearn

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  1. One of the above repairs has been performed. If not, do not continue.
  2. Install the scan tool. Start the engine.
  3. Operate the vehicle until the engine coolant temperature is more than 170°F (77°C). Clear all of the DTC codes.
  4. Turn ON the ignition, with the engine OFF. Hold the accelerator pedal in the wide open throttle (WOT) position for a minimum of 45 seconds (this step prepares the PCM to activate the offset learn (internal).
  5. Turn OFF the ignition for 30 seconds. In this step, the PCM is being powered down.
  6. Start the engine.
  7. Verify in the scan tool that Engine Coolant Temperature (ECT) is more than 170°F (77°C). If not, operate the vehicle until the desired ECT is achieved. The vehicle can be driven or the throttle can be depressed until the correct coolant temperature is achieved.
  8. As soon as the ECT is more than 170°F (77°C) and the engine speed is below 1500 RPM, the PCM automatically learns a new offset.
  9. A new offset will over write the previous one. The TDC offset should be between -0.25 to -0.75. If the TDC offset is within the specified value, the procedure is complete. Otherwise, continue to the next step, adjusting the injection pump.
  10. Turn OFF the engine.
  11. Loosen injection pump flange nuts using the Injection Pump Wrench.
  12. Slightly rotate the injection pump (1 mm equals 2 degrees). Use the Injection Pump Adjustment Tool to rotate injection pump, and tighten injection pump flange nuts. Rotate pump toward driver side. A positive (+) number, rotate toward passenger side in order to achieve a negative (-) number (1 mm equals 2 degrees).
  13. If you are unable to set the correct TDC offset, check the following conditions:
    • The engine coolant temperature (ECT) is more than 170°F (77°C).
    • All PCM and injection timing stepper motor connections are secure.
    • The Techline terminal/equipment is for the latest software version.
    • The base installation of the injection pump is correct - The injection pump ESO solenoid should be approximately straight up and down.
    • If all checks have been performed, the injection pump may be malfunctioning. However, this is an extremely unlikely failure.
  14. Repeat steps  6- 8 until correct TDC offset has been achieved. Its possible that the injection pump may be adjusted multiple times until the specified value is achieved.
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