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2005 Colorado with 3.5l. I changed the crankshaft position sensor for various reasons and am wondering if the vehicle needs a CASE relearn? I hear yes and no from different mechanics. When I first tried to start the truck after replacement it would turn over but not start so I let the computer sit unplugged overnight and it seems to start fine now but still not sure if it hesitates a little longer than before. Need a few more starts to know for sure... Not sure if this is a sign of it needing to be relearned or a defective part?
 

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The shop manual directs you have to perform a "CKP System Variation Learn Procedure" when you replace the sensor.

Here's the procedure, but you need the "scan tool":

CKP SYSTEM VARIATION LEARN PROCEDURE



  1. Install a scan tool.
  2. Monitor the powertrain control module (PCM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information for the applicable DTC.
  3. Select the crankshaft position (CKP) variation learn procedure with a scan tool.
  4. The scan tool instructs you to perform the following:
  5. Accelerate to wide open throttle (WOT).
  6. Release the throttle when fuel cut-off occurs.
  7. Observe the fuel cut-off for the applicable engine.
  8. The engine should not accelerate beyond the calibrated RPM value.
  9. Release the throttle immediately if value is exceeded.
  10. Block the drive wheels.
  11. Set the parking brake.
  12. DO NOT apply the brake pedal.
  13. Cycle the ignition from OFF to ON.
  14. Apply and hold the brake pedal.
  15. Start and idle the engine.
  16. Turn the A/C OFF.
  17. The vehicle must remain in Park or Neutral.
  18. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components:
  • Crankshaft position (CKP) sensor activity-If there is a CKP sensor condition, refer to the applicable DTC.
  • Camshaft position (CMP) signal activity-If there is a CMP signal condition, refer to the applicable DTC.
  • Engine coolant temperature (ECT)-If the engine coolant temperature is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
  1. Enable the CKP system variation learn procedure with the scan tool and perform the following:
  1. Accelerate to WOT.
  2. Release the throttle when fuel cut-off occurs.
  3. Test in progress
IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.



  1. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315. If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information for the applicable DTC.
  2. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether or not DTC P0315 is set:


  • An engine replacement
  • A PCM replacement
  • A crankshaft balancer replacement
  • A crankshaft replacement
  • A CKP sensor replacement
  • Any engine repairs which disturb the crankshaft to CKP sensor relationship.
 
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