Crank relearn

[DodgeZ]

I read this as the PCM uses the crank relearn to figure out where zero is for crank and crank sensor combo. Then your timing for fuel and spark use that. Am I wrong? With a lopey cam, I am nor sure how the PCM figures out zero. I guess it may not matter much. I am not sure what the range that your reluctor wheel and CKP sensor combo could be off, a -+ 1,2,3 degrees. Do any of the tools show the values learned by the PCM? I am wonder if you can adjust the lower RPM value with some of learned value from the mid range RPM, post cam stumbles. We don't have a timing light, how would you "degree" in the engine to PCM to know exactly what TDC is for your combo.



"The following text is quoted from the 1999 GM F-Body Factory Service Manual:

Circuit Description

The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more then an expected amount, the PCM interprets this as a misfire. The interval between the CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult: Crankshaft, Reluctor wheel, CKP sensor. The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position Variation Learning Procedure again.


Perform the learning procedure after the following actions: A PCM replacement, Any operation or repair involving the crankshaft, the CKP sensor, or the CKP to reluctor wheel gap relationship, An engine replacement, The ignition switch is in the ON position until the battery is drained."