Comprehensive diagnostic guide for OBD-II code P0315

Code: P0315
Full definition (from open-source code definitions): Crankshaft Position Variation Not Learned (Posição do virabrequim - variação do sistema não apreendida). This corresponds to a learn/verification status for the crankshaft position variation that the PCM expects to be learned during normal operation.

Context and classification

• Code category: Powertrain. This is a powertrain diagnostic code that relates to engine timing reference learning, not a direct sensor fault by itself.
• Source notes: OBD-II systems monitor many parameters via the PCM/ECU and generate codes when issues are detected. P0315 is listed as a crankshaft position variation learn/learn-not-completed condition in the open-source definition. For general framework, see Wikipedia's OBD-II sections on Diagnostic Trouble Codes and Powertrain Codes.

Symptoms

• Check Engine Light (CEL) or MIL illuminated with P0315 stored in PCM.
• Engine runs irregularly, rough idle, or intermittent misfires during learn attempts.
• Vehicle may not pull consistently during acceleration while the PCM attempts to learn variation.
• Possible failure to enter or complete a crankshaft variation learn procedure after events such as battery disconnect, PCM reset, or replacement of related hardware.

Probable Causes

Note: Specific NHTSA complaint statistics for P0315 are not provided . The probability estimates below are grounded in general ASE field experience and typical OE guidance. The highest likelihood cause is usually that the crankshaft variation learn procedure was not completed or memory was lost, often after battery service or PCM reset. If the vehicle has no genuine learn procedure, the code should clear only after a successful learn drive cycle.

• Primary cause: Crankshaft Position Variation Learn not completed or memory lost

  • Estimated probability: 40-60%

• Related to sensor/wiring issues that hinder learning (crankshaft position sensor circuit)

  • Estimated probability: 15-25%

• Mechanical timing or engine integrity issues (timing belt/chain, tensioner, reluctor wheel, or mechanical slop)

  • Estimated probability: 5-15%

• PCM/ECU hardware or software fault

  • Estimated probability: 5-10%

• Miscellaneous/other (sensor alignment, dirty reluctor, corrosion, connector issues)

  • Estimated probability: 5-10%

Diagnostic Approach

This guide follows a logical flow: confirm and attempt the learn, then check related systems if learn fails. Adapt to vehicle-specific procedure per the service manual.

1) Confirm the code and gather context

• Use a compatible scan tool to confirm P0315 and note any accompanying DTCs (e.g., P0335 Crankshaft Position Sensor A Circuit, P0340 Camshaft Position Sensor, P030x misfire codes, etc.).
• Check for any pending vs stored codes and review freeze-frame data for engine status at the time of the fault.
• Confirm if the vehicle has recently undergone battery service, PCM replacement, or an ECU reflash.

2) Attempt the Crankshaft Position Variation Learn procedure

• Many modern vehicles require a dedicated "Crankshaft Position Variation Learn" procedure through the scan tool. If your tool supports it, perform the learn while the engine is at normal operating temperature and the vehicle is in a safe, stationary condition (e.g., Park/Neutral with parking brake engaged).
• If the learn procedure completes successfully, clear the codes and perform a drive cycle to confirm stability. Note: the learn procedure and drive cycle requirements vary by manufacturer; follow the vehicle-specific procedure in the service information.
• If the learn procedure does not complete or fails, proceed to next steps. Do not assume the vehicle is fixed just because the learn was initiated.

3) Inspect related engine electrical and sensors

• Crankshaft position sensor circuit:
  • Check for proper resistance (as per service specs) and continuity in the sensor wiring.
  • Inspect the sensor connector and grounds for corrosion, oil contamination, and secure fit.
  • Look for intermittent voltage drops or signal distortion in the sensor output.
• Related sensors and circuits:
  • Camshaft position sensor (P0340 family) and ignition system components that could affect engine timing and signal stability.
  • Ensure there are no ongoing misfire conditions (P0300-P0308) that could complicate learn.

4) Inspect mechanical timing and engine integrity (when Learn repeatedly fails or if symptoms indicate timing issues)

• Inspect timing belt/chain, tensioner, guides, and sprockets for wear, skip, or misalignment.
• Check timing marks and confirm the timing event has not slipped since last known good state.
• If applicable, inspect the reluctor ring and crankshaft position tone wheel for damage, debris, or misalignment.
• Consider a compression test or cylinder leak-down test if mechanical concerns are suspected or if misfire history is significant.

5) Inspect PCM/ECU health and software

• Confirm there are no pending ECU software updates or reflash advisories for your vehicle model.
• If multiple engine-related DTCs exist or the vehicle exhibits unusual behavior, consider ECU health assessment or professional reflash/settle (with OEM software).

6) Road test and drive cycle validation

• After a successful learn or following repairs, perform a defined drive cycle (as specified by the manufacturer) to allow the PCM to consolidate the learned variation.
• Monitor for the reoccurrence of P0315 and any other related codes during the drive cycle.

7) If the code returns after attempting learn and validation

• Revisit the sensor circuit integrity (step 3) and mechanical timing checks (step 4).
• Reassess the need for a PCM replacement or reflash if software-related issues are suspected (step 5).

Safety Considerations

• Work in a well-ventilated area; avoid hot surfaces and moving parts when the engine is running.
• Follow standard electrical safety: disconnect the battery only when appropriate (and with engine off), avoid shorting ignition circuits.
• Use proper PPE and ensure the vehicle is securely supported if performing under-vehicle inspections.

How to document and communicate findings

• Record the exact procedure used for the crankshaft variation learn, any errors returned by the tool, and the final status (completed, failed, or not attempted).

• Note all related DTCs present during testing, as well as freeze-frame data and any observed drive-cycle results.

• Provide a concise repair plan with the rationale: e.g.,

• OBD-II overview and code framework (Powertrain Codes, Diagnostic Trouble Codes) from Wikipedia's OBD-II sections: These provide general context on how DTCs are used, and how powertrain codes are categorized and used in diagnostics. They support the classification and high-level troubleshooting approach.

  • OBD-II > Diagnostic Trouble Codes
  • OBD-II > Powertrain Codes
  • OBD-II > Emissions Testing

• Open-source code definition for P0315: Posição do virabrequim - variação do sistema não apreendida, which identifies P0315 as Crankshaft Position Variation Not Learned.

  • Source: GitHub OBD2 CODE DEFINITIONS (Portuguese description aligns with Crankshaft Position Variation Not Learned)

Summary

• P0315 indicates that the crankshaft position variation learn did not complete or memory was not learned. The most common root cause is battery/ECU memory loss or an incomplete learn procedure. Start with verifying and performing the crankshaft variation learn, then systematically check sensor circuits, wiring, and mechanical timing as needed. If the learn fails again, expand investigation to sensor integrity and engine timing, and consider ECU/software health. Always follow vehicle-specific service manuals for exact learn procedures and drive-cycle requirements.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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