Depends on if you have access to a scan tool.
A.) Do, follow this procedure *
B.) If NOT, follow this procedure **
With a scan tool:
Set the parking brake.
Block the drive wheels.
Ensure the hood is closed.
With the scan tool, monitor for DTCs. If a DTC is set, refer to Diagnostic Trouble Code (DTC) List/Type before proceeding.
Start the engine and allow engine coolant temperature to reach at least 70°C (158°F).
Turn OFF the ignition.
Select and enable the crankshaft position variation learn procedure with the scan tool.
Start the vehicle.
Apply and hold the service brake pedal firmly.
Ensure the transaxle is in park.
Increase accelerator pedal position until the fuel cutoff is reached at 5150 RPM. Immediately release the accelerator pedal after fuel cutoff is reached.
The crankshaft position system variation compensating values are learned when the RPM decreases back to idle. If the procedure terminates.
Recheck the ECM with a fresh 'scan' and see if the code "P1336" dispalys "Pass" or "Fail".
If it says "Fail" then preform the procedure again.
If the Crankshaft Variation Relearn is not accessible through your scan tool (some truck applications 1998 & later) perform the relearn in the following manner:
1. Turn off all of the accessories. With the Air temperature sensor and Coolant temperature within 5 degrees (Centigrade) of each other, start the engine and let it idle in Park or Neutral for two minutes.
2. Accelerate the vehicle to 55 mph at part throttle. Cruise at 55 mph for 8- 10 minutes until the engine reaches operating temperature.
3. Cruise at 55 mph for another 5-6 minutes.
4. Decelerate to 45 mph without using the brakes, and maintain 45 mph for 1 minute.
5. Perform 4 deceleration cycles, without using the brakes, of 25 seconds each where no specific speed is necessary. Returning to 45 mph for 15 seconds in between deceleration cycles.
6. Accelerate to 55 mph and cruise for 2 minutes.
7. Stop the vehicle and idle for 2 minutes with the brake applied and the transmission in Drive.
Lots of good info on here also - http://www.fullsizechevy.com
Same info is in this reply - http://www.fullsizechevy.com/forums/...t-relearn.html