P0315: Crankshaft variation data that are absent or invalid in memory

P0315 concerns crankshaft position variation learning. The cited GM diagnostic checks the learned angular spacing between reluctor-wheel teeth stored in controller memory. The sum should represent one complete revolution: 360 degrees.

A memory-validity check, not a missing pulse code

The published failure criterion is a difference greater than 0.001 degrees between the summed learned angles and 360 degrees. Default or corrupted values can fail this consistency check. The document names loss of nonvolatile memory or a memory error as ways the learned values can become defaulted or incorrect.

This means a plausible live engine-speed signal does not prove the learning data are valid. Conversely, P0315 alone does not establish that the crankshaft sensor has stopped producing pulses or that a reluctor tooth is physically damaged.

Establish learning status first

Preserve the controller's variation-learn status and any available history of programming, memory clearing or interrupted learning. The source requires its manufacturer enable counter to be zero and lists a half-second diagnostic time with continuous 100-millisecond execution.

Use the applicable service procedure to determine why learning is invalid and whether a specified relearn is appropriate. This page does not provide that procedure or justify an improvised high-speed engine routine. Verification requires accepted learned data and a passing consistency check, not merely a cleared P0315 or an engine that starts normally.

Source and applicability

This explanation is limited to the 2025 GM 25OBDG03A monitor on page 257. Its thresholds are calibration examples, not universal specifications. Confirm the vehicle, engine and controller procedure before applying them.