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GM-Merlin, I have aquestion for you. Why the 70 deg C or 158 deg F temp engine coolant temp in order to program the Crankshaft Position (System)Variation Learn Procedure?
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For a number of reasons, first the engine has to be warmed up some so the clearances are reduced , next the engine needs to be in closed loop (this is when the PCM is using sensor input to control engine operation instead of a preprogrammed strategy).
Now these are just the parameters that need to be met to perform the procedure, not the parameters used for Angle based timing.
The Angle based timing strategy is used as soon as the CKP sensor sees the notch in the reluctor pass both the A and B sensor (less than a 30degree rotation of the crankshaft) if the PCM sees both sensor A and B inputs, the Angle based timing is used, if the PCM sees only 1 sensor input the SES light is turned on and the PCM bases timing on the sensor input it saw.
In a nutshell, Angle timing is more percise