GM Service Manual Online
For 1990-2009 cars only

Camshaft Retard Offset Testing Procedure

The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:

  1. With the ignition OFF, install a scan tool to the data link connector (DLC).
  2. Start the engine and bring to normal operating temperature.
  3. Important: The Cam Retard Offset reading will not be accurate below 1,000 RPM

  4. Increase engine speed to 1,000 RPM.
  5. Monitor the Cam Retard Offset.
  6. If the Cam Retard indicates a value of 0° ± 2°, the distributor is properly adjusted.
  7. If the Cam Retard does not indicate 0° ± 2°, the distributor must be adjusted.

Adjustment Procedure

  1. With the engine OFF, slightly loosen the distributor hold down bolt.
  2. Important: The Cam Retard Offset reading will not be accurate below 1,000 RPM

  3. Start the engine and raise engine speed to 1,000 RPM.
  4. Using a scan tool, monitor the Cam Retard Offset.

  5. Object Number: 18446  Size: SH
  6. Rotate the distributor as follows:
  7. 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
    4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction.
  8. Repeat step 4 until 0° ±2° is obtained.
  9. Turn the ignition OFF.
  10. Tighten the distributor hold-down bolt to 3N·m (25 lb. ft.).
  11. Start the engine, raise engine speed to 1,000 RPM, and recheck the Camshaft Retard Offset.