GM Service Manual Online
For 1990-2009 cars only

Camshaft Retard Offset Test

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 the scan tool.
  2. Start the engine and bring to normal operating temperature.
  3. Important: Cam Retard Offset reading will not be accurate below 1000 RPM

  4. Increase engine speed to 1000 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.

Adjusting Camshaft Retard Offset


    Object Number: 18446  Size: SH
  1. With the engine OFF, slightly loosen the distributor hold down bolt.
  2. Important: Cam Retard Offset reading will not be accurate below 1000 RPM

  3. Start the engine and raise engine speed to 1000 RPM.
  4. Using a scan tool monitor Cam Retard Offset.
  5. Rotate the distributor as follows:
  6. 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.
  7. Repeat step 4 until 0° ±2° is obtained.
  8. Turn the ignition OFF.
  9. Tighten the distributor hold-down bolt to 3N·m(25 lb. ft.).
  10. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset.