Crankshaft relearn explained

[farmtruc]

Hi Guys, this code may pop up on 1 of 30 trucks that get a pcm upgrade. Here's a nice explanation of what the P0315 is.
To fix it, get in touch with a shop that has a tool similar to a techII, genisys, or even efi live with the bi directional controls. Some shops are cool and will perform the procedure for a very little fee, others will act like they are hi-tech and only they can do it, move on if you run into those shops.

here's the info:

DTC P0315
Circuit Description
The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, and the CKP sensor. The calculated error allows the powertrain control module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wide range of engine speed and load. If the CKP system variation values are not stored in the PCM memory, DTC P0315 sets.

Conditions for Running the DTC
DTCs P0335, P0336, P0341, P0342, or P0343 are not set.

Conditions for Setting the DTC
The CKP system variation values are not stored in the PCM memory.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
The CKP system variation values are not stored in the PCM memory after a learn procedure has been performed. If the actual CKP variation is not within the CKP system variation compensating values stored in the PCM, DTC P0300 may set.

The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set.

An engine replacement
A PCM replacement
A harmonic balancer replacement
A crankshaft replacement
Any engine repairs which disturb the CKP sensor relationship If the CKP system variation learn procedure cannot be performed successfully, check for the following conditions and correct as necessary:

A damaged reluctor wheel
Excessive crankshaft runout
A damaged crankshaft
Interference in the signal circuit of the CKP sensor A coolant temperature that is not within the Conditions For Running the DTC The ignition switch is in the ON position until the battery is drained A PCM power disconnect with the ignition ON may erase the stored value and set the DTC P0315

[onyx]

Originally posted by farmtruc@Jul 23 2004, 07:13 PM
this code may pop up on 1 of 30 trucks that get a pcm upgrade.

how long ago was this?....

[revolution]

i got this code on my truck. it was after maybe 1200 miles on the 91 tune. i doubt it had anything to do with the tune.

im still under warranty, so took it into the dealership. they said it was a broken craftshaft sensor. for the dealership to replace the sensor and do the relearn it would have been ~ $160.