GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Riviera 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Crankshaft Position System Variation Learn

The crankshaft position system variation compensating values are stored in the PCM non-volatile memory after a learn procedure has been performed. If the actual crankshaft position system variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set (refer to Diagnostic Aids for DTC P0300 Engine Misfire Detected ).

The Crankshaft Position System Variation Learn Procedure should be performed if any of the following conditions are true:

    • DTC P1336 is set.
    • The PCM has been replaced.
    • The engine has been replaced.
    • The crankshaft has been replaced.
    • The crankshaft harmonic balancer has been replaced.
    • The crankshaft position sensor has been replaced.

Caution: Before performing the Crankshaft Position System Variation Learning Procedure always set the vehicle parking brake and block the drive wheels in order to prevent personal injury. Release the throttle immediately when the engine starts to decelerate in order to eliminate over revving the engine. Once the learn procedure is completed, the control module will return engine control to the operator and the engine will respond to the throttle position.

Important: Begin the crankshaft position system variation learn procedure with the ignition OFF. Do not turn ON the ignition switch or start the vehicle unless instructed to do so by the scan tool.

The scan tool crankshaft position system variation learn function will be inhibited if any powertrain DTCs other than DTC P1336 are set before or during the crankshaft position system variation learn procedure. Clear the DTCs before attempting to perform the crankshaft position system variation learn procedure. If any DTCs reset, the DTCs must be diagnosed and repaired before the crankshaft position system variation learn procedure can be successfully completed.

The crankshaft position system variation learn function will be inhibited if the PCM detects a malfunction involving the camshaft position signal circuit, the 3X reference circuit, or the 18X reference circuit.

   • If the scan tool indicates that a problem with the camshaft position signal exists, refer to DTC P0341 Camshaft Position (CMP) Sensor Performance .
   • If the scan tool indicates that a problem with the 3X crank signal exists, refer to DTC P1374 Crankshaft Position (CKP) High to Low Resolution Frequency Correlation .
   • If the scan tool indicates that a problem with the 18X crank signal exists, refer to DTC P0336 Crankshaft Position (CKP) Sensor Circuit .
The scan tool crankshaft position system variation learn function will not be enabled until engine coolant temperature is greater than 70°C (158°F).

Selecting the crankshaft position system variation learn procedure on the scan tool will command the PCM to enable CKP system variation learn fuel cutoff and allow the crankshaft position system compensating values to be stored in the PCM. The PCM must detect an engine speed of 5150 RPM (CKP system variation learn fuel cutoff) during the crankshaft position system variation learn procedure to store the crankshaft position system compensating values and complete the procedure.

  1. Set the parking brake.
  2. Block the drive wheels.
  3. Ensure that the hood is closed.
  4. Start the engine and allow engine coolant temperature to reach at least 70°C (158°F).
  5. Turn OFF the ignition.
  6. Select and enable the crankshaft position variation learn procedure with the scan tool.
  7. Start the vehicle
  8. Ensure that the transaxle is in Park.
  9. Apply and hold the service brake pedal firmly.
  10. Increase accelerator pedal position until CKP system variation learn fuel cutoff is reached. CKP system variation learn fuel cutoff is reached at 5150 RPM. Immediately release the accelerator pedal when fuel cutoff is reached.
  11. The crankshaft position system variation compensating values are learned when RPM decreases back to idle. If the procedure terminates, refer to Important above for instructions.
  12. Observe DTC status for DTC P1336.
  13. If the scan tool indicates that DTC P1336 ran and passed, the crankshaft position system variation learn procedure is complete. If the scan tool indicates DTC P1336 failed or not run, check for other DTCs. If no DTCs other than P1336 are set, repeat the crankshaft position system variation learn procedure as necessary.