Tech 2 Crankshaft Position Variation Learn Procedure Tips - keywords case CKP crank data DTC ECM P0300 P0315 P1781 U0401 PCM relearn

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some technicians may find that the Crankshaft Position Variation Learn is not successful when following the directions on the Tech 2.

If the Tech 2 Crankshaft Position Variation Learn procedure is not successful by following the Tech 2 instructions, the following information may help:

1. Make sure the Tech 2 is updated to the latest software version.
2. Follow all Tech 2 screen instructions until "test in progress" starts to flash on the screen. Once this occurs, continue to Step 3 below.

Note: There is not a message on the Tech 2 screen that advises "accelerate to wide open throttle" like most domestic GM vehicles have. On this vehicle, a "test in progress" message will start to flash before the accelerator pedal is pressed.

3. With the "test in progress" message flashing, the transmission in park, and the brakes applied, accelerate to wide open throttle and hold it in fuel cut off mode until a "learned this ignition" message is displayed. During this learn process, the RPM will fluctuate from approximately 1,000 - 4,500 RPM while fuel cut off mode is enabled.

Note: Once the "learned this ignition" message is received, the Crankshaft Position Variation Learn procedure has been completed. Another Crankshaft Position Variation Learn will not be allowed until the Tech 2 and ignition switch are both turned off for 30 seconds or more. If another relearn is attempted without turning the Tech 2 and the ignition switch off for more than 30 seconds, "accelerate to wide open throttle" will flash on the Tech 2 screen, the RPM will be allowed to exceed 6,000 RPM, and the Crankshaft Position Variation Learn will not be successful because fuel cut off mode was not enabled.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.