LQ4 to LQ9, with Truck Norris NSR: random misfire with rough idle and dies in gear

[blindsquirrel]

DTC P0315:

The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight build tolerance variations in the CKP sensor, crankshaft, and CKP sensor position. The calculated error allows the engine control module (ECM) to accurately compensate for reference period variations. This enhances the ability of the ECM to detect misfire events over a wide range of engine speeds and load conditions. The ECM stores the Crankshaft Position System Variation values after a learn procedure has been performed. If the actual crankshaft position variation is not stored within the CKP compensating value look up table, then DTC P0300 may set. If the CKP system variation values are not stored in the ECM memory, or a proper ECM power down does not occur after completing the CKP Learn Procedure, then DTC P0315 sets.

Note that when they say "CKP sensor position" they mean radial (the air gap), not angular (relation to true TDC). During the CKP learn it is recording what the pattern for that particular wheel with that particular sensor with that particular air gap is supposed to look like. Each tooth and gap on the wheel is different enough that they will have a very slightly different signal output.

Also of note, in the manuals GM considers the crankshaft and reluctor to be the same thing, not serviced separately, so when they say "the crankshaft", in this case they mean the reluctor.

Nowhere in the stock ECM/PCM is there the ability to correct for or determine or display the actual offset between true TDC and what the reluctor says is TDC. You CAN adjust that offset in aftermarket ECUs.