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P0315 Code: Crankshaft Position System Variation Not Learned

P0315 crankshaft position variation not learned diagnostic guide

The P0315 OBD-II trouble code means the engine control module does not have a valid crankshaft position variation value stored in memory.

The generic definition is:

P0315 — Crankshaft Position System Variation Not Learned

P0315 does not automatically mean the crankshaft position sensor has failed.

In many cases, the engine computer needs a crankshaft variation relearn after the crankshaft sensor, PCM, engine, flywheel, flexplate, crankshaft, reluctor wheel, or timing components have been replaced or disturbed.

The relearn teaches the PCM the small manufacturing and mechanical variations unique to that engine’s rotating assembly. Without that information, the computer may struggle to distinguish normal crankshaft-speed changes from an actual engine misfire.

P0315 is therefore a calibration code—not simply another invitation to replace the crankshaft sensor.

P0315 belongs to the powertrain-code family covered in the complete Pro Street P-code OBD-II guide.

P0315 Quick Answer

ItemInformation
Trouble codeP0315
DefinitionCrankshaft Position System Variation Not Learned
SystemEngine position monitoring and misfire detection
SeverityModerate
Safe to drive?Usually briefly if the engine runs normally and no serious companion codes are present
Most common causeRequired crankshaft variation relearn has not been completed
Other causesSensor signal fault, reluctor damage, wiring, incorrect installation, or PCM issue
Typical solutionDiagnose related faults and perform the manufacturer’s relearn procedure
Related codesP0314, P0335–P0339, P0300 and cam/crank correlation codes
Typical repair rangeApproximately $100 to $3,000+, depending on the underlying cause

What Does P0315 Mean?

The crankshaft position sensor monitors the crankshaft’s rotational position and speed.

The engine control module uses this information to manage:

No crankshaft, reluctor wheel, flywheel, or flexplate is perfectly identical to every other one produced. Tiny physical variations can create minor changes in the crankshaft position signal.

During a crankshaft variation relearn, the PCM measures these normal variations and stores them as a reference.

The learned value helps the PCM distinguish:

If the variation value is missing, incomplete, invalid, or outside the expected range, the PCM may store P0315.

Is P0315 a Crankshaft Sensor Failure?

Not necessarily.

P0315 means the crankshaft variation value has not been learned or accepted. It does not directly mean the sensor circuit has failed.

Compare P0315 with P0335:

CodeMeaning
P0315Crankshaft position variation calibration is missing or invalid
P0335Crankshaft Position Sensor “A” circuit malfunction
P0336Crankshaft Position Sensor “A” range or performance fault
P0339Crankshaft Position Sensor “A” circuit intermittent

P0335–P0339 provide stronger evidence of a sensor, circuit, signal, air-gap, or reluctor-wheel problem.

P0315 commonly means the PCM needs to relearn the system after a repair. Replacing the sensor again will not complete the relearn, although it may make the parts supplier feel appreciated.

For vehicle-specific sensor service information, see our P0335 crankshaft position sensor guide.

What Is a Crankshaft Variation Relearn?

A crankshaft position variation relearn is a calibration procedure that allows the PCM to measure the unique rotational characteristics of the engine.

During the procedure, the PCM observes crankshaft acceleration and deceleration while the engine is operated under specific conditions.

Depending on the manufacturer, the relearn may involve:

The exact procedure varies by vehicle.

Some vehicles require an enhanced scan tool. Others may learn the variation automatically during normal driving or through a manufacturer-specific sequence.

Never assume that a procedure written for one manufacturer applies to another vehicle.

Why Is Crankshaft Variation Learning Important?

The PCM detects many engine misfires by measuring tiny changes in crankshaft speed.

A weak combustion event causes a slight reduction in crankshaft acceleration. The PCM compares that change with the learned characteristics of the rotating assembly.

Without an accurate variation value, normal mechanical irregularities may resemble a misfire.

An incomplete or incorrect relearn may contribute to:

The calibration does not change engine timing or repair a mechanical failure. It teaches the PCM what normal crankshaft variation looks like on that particular engine.

What Repairs Can Trigger P0315?

P0315 may appear after work involving:

Not every vehicle requires a relearn after all these repairs. Follow the manufacturer’s service information for the specific application.

Common P0315 Conditions

A vehicle with P0315 may experience:

Many vehicles run normally with P0315 because the code involves calibration rather than a complete loss of crankshaft position data.

If the engine stalls, fails to start, or runs severely rough, look for additional sensor, circuit, timing, or mechanical faults.

How Serious Is P0315?

P0315 is generally moderate in severity.

The vehicle may continue running because the PCM still receives a crankshaft position signal. However, misfire detection may be unreliable until the variation value is learned.

P0315 should be diagnosed promptly because it may:

Stop Driving If:

Those conditions indicate a problem beyond an incomplete relearn.

Most Common Causes of P0315

Possible causeRelative likelihood
Crankshaft variation relearn not completedVery high
PCM recently replaced or programmedHigh
Crankshaft sensor recently replacedHigh
Engine, flywheel or flexplate recently servicedHigh
Incorrect crankshaft sensor installationMedium
Damaged crankshaft sensor wiringMedium
Incorrect sensor air gapApplication dependent
Damaged or loose reluctor wheelMedium
Flywheel or flexplate damageMedium
Timing-system problemLower
Low battery or charging voltageLower
PCM software or memory problemLower
Failed PCMRare

Recent repair history is especially important. If P0315 appeared immediately after sensor, engine, transmission, or PCM work, determine whether the relearn was required and completed.

How to Diagnose P0315

Step 1: Confirm P0315

Connect an enhanced scan tool and record:

Do not clear the code until all information has been recorded.

Important freeze-frame information may include:

Step 2: Ask What Was Recently Repaired

Determine whether P0315 appeared after:

If the code appeared immediately after one of these procedures and no other faults are present, a missing relearn becomes the leading possibility.

Step 3: Check for Related Codes

P0315 may appear with:

Companion codes determine whether a relearn should be attempted.

Code combinationDiagnostic direction
P0315 only after sensor or PCM workVerify prerequisites and perform relearn
P0315 plus P0335Diagnose the crankshaft sensor circuit first
P0315 plus P0336Inspect signal quality, air gap and reluctor wheel
P0315 plus P0016Inspect mechanical timing and cam/crank correlation
P0315 plus P0300Confirm that no active combustion fault exists
P0315 plus low-voltage codesTest battery, charging system, grounds and power supply

Do not begin a relearn while unresolved crankshaft sensor, timing, voltage, or active misfire faults remain.

Step 4: Inspect Battery and Charging Voltage

A relearn may fail if system voltage is unstable.

Inspect:

Use manufacturer voltage specifications.

Some scan tools will cancel the relearn if voltage falls outside an acceptable range. Others may simply leave you staring at a failed procedure and reconsidering your relationship with electricity.

Step 5: Inspect the Crankshaft Sensor Installation

If the sensor was recently replaced, verify:

An incorrectly installed sensor may produce a signal strong enough for the engine to run but too distorted for the PCM to complete the variation relearn.

Step 6: Inspect Crankshaft Sensor Wiring

Check the harness for:

Use wiring diagrams and manufacturer specifications.

Depending on the sensor design, testing may include:

Do not rely only on resistance testing. Some sensors fail dynamically with heat, vibration, or engine speed.

Step 7: Inspect the Reluctor Wheel

The crankshaft position sensor reads a toothed reluctor wheel or tone ring.

Possible problems include:

A damaged reluctor may allow the engine to run while preventing the PCM from learning an acceptable variation pattern.

An oscilloscope is often the best tool for identifying an irregular reluctor waveform.

Step 8: Inspect the Flywheel or Flexplate

On some engines, the crankshaft sensor reads timing features incorporated into the flywheel or flexplate.

Inspect for:

If P0315 appeared after a clutch, transmission, flywheel, or flexplate replacement, verify that the installed component matches the engine and PCM calibration.

A component that bolts on successfully is not automatically the correct component. Manufacturers occasionally reserve that surprise for after the transmission is reinstalled.

Step 9: Verify Mechanical Timing

Incorrect valve timing can alter crankshaft acceleration patterns and prevent a successful relearn.

Inspect:

If correlation codes such as P0016 are present, repair the timing problem before attempting a relearn.

Step 10: Confirm That No Active Misfire Exists

A crankshaft variation relearn should not be performed to conceal an actual combustion problem.

Monitor:

If the engine is actively misfiring, repair that problem first.

The relearn teaches the PCM normal engine variation. An actively misfiring engine is not demonstrating normal variation, regardless of how politely the scan tool asks.

Crankshaft Variation Relearn Prerequisites

Exact prerequisites vary, but manufacturers commonly require some combination of:

Always follow the service information for the specific year, make, model, engine, and PCM calibration.

How to Perform a Crankshaft Variation Relearn

Important Safety Warning

Some crankshaft relearn procedures require the engine to accelerate rapidly toward a manufacturer-controlled fuel cutoff.

This can involve high engine speed.

Before beginning:

Do not perform a generic internet procedure on an unsupported vehicle.

If the engine has internal damage, low oil pressure, overheating, severe misfire, timing noise, or an unknown mechanical condition, do not attempt the relearn.

General Scan-Tool Procedure

A typical scan-tool relearn may follow this general sequence:

  1. Connect a compatible enhanced scan tool.
  2. Verify that P0315 and related codes have been recorded.
  3. Repair active sensor, timing, voltage, or misfire faults.
  4. Warm the engine to the specified temperature.
  5. Turn off accessories.
  6. Apply the parking brake.
  7. Hold the service brake if instructed.
  8. Select the crankshaft variation relearn function.
  9. Follow all scan-tool prompts.
  10. Accelerate the engine only when commanded.
  11. Release the accelerator immediately when instructed.
  12. Allow the engine to return to idle.
  13. Confirm that the scan tool reports a successful relearn.
  14. Clear codes if instructed.
  15. Complete the required drive cycle.
  16. Rescan for P0315 and pending codes.

This is a general overview, not a substitute for the manufacturer procedure.

What If the Relearn Completes Successfully?

After a successful relearn:

A permanent P0315 may remain visible until the PCM completes enough successful self-tests.

What If the Relearn Will Not Start?

If the scan tool refuses to begin, check:

A sensor input that looks reasonable on the dashboard may still fall outside the PCM’s relearn enable window.

What If the Relearn Starts but Fails?

Possible causes include:

Do not repeatedly perform high-RPM relearn attempts without finding the reason for failure.

The procedure is a calibration event, not an endurance test.

Can P0315 Cause False Misfire Codes?

Yes.

The PCM uses the learned crankshaft variation value to interpret rotational speed changes. Without the correct baseline, normal mechanical variation may resemble weak combustion.

Possible companion codes include:

However, P0315 does not prove that every misfire code is false.

If the engine shakes, misfire counters increase consistently, spark or injector faults are present, or compression is low, repair the actual combustion failure.

Performing a relearn should not replace normal diagnosis.

Common P0315 Repairs and Costs

RepairApproximate installed cost
Crankshaft variation relearn$100–$300
Battery or terminal service$50–$400
Repair crankshaft sensor wiring$100–$800
Replace crankshaft position sensor$150–$600
PCM programming or update$150–$500
Replace damaged reluctor wheel$500–$3,000+
Replace flywheel or flexplate$800–$3,000+
Correct timing-system installation$800–$4,000+
Replace PCM$800–$2,500+
Repair internal engine problem$1,500–$10,000+

Actual costs depend on the vehicle, component location, labor rate, and underlying problem.

A relearn may take only a short time. Reaching a damaged reluctor wheel may require considerably more enthusiasm and transmission removal.

Common P0315 Diagnostic Mistakes

Replacing the Crankshaft Sensor Automatically

P0315 frequently indicates a missing calibration rather than a failed sensor.

Performing the Relearn Before Checking Related Codes

Crankshaft sensor, camshaft sensor, timing, voltage, and active misfire faults should be repaired first.

Using the Wrong Relearn Procedure

Procedures differ by manufacturer, engine, PCM and model year.

Ignoring Recent Repair History

P0315 often appears immediately after sensor, PCM, engine, transmission, flywheel, or timing work.

Attempting the Relearn on a Damaged Engine

Do not command a high-RPM event when the engine has low oil pressure, overheating, mechanical noise, severe misfire, or suspected timing damage.

Ignoring the Reluctor Wheel

A new sensor cannot correct a bent, cracked, loose, or incorrectly installed reluctor wheel.

Assuming a Successful Relearn Fixed Every Misfire

A calibration can restore accurate monitoring. It cannot repair a worn plug, failed coil, restricted injector, or burned valve.

Repeatedly Clearing P0315

Clearing the code does not create the missing variation value.

P0315 Frequently Asked Questions

What does P0315 mean?

P0315 means the PCM does not have a valid crankshaft position variation value stored or learned.

Does P0315 mean the crankshaft sensor is bad?

Not necessarily. The system may only need a relearn after recent repairs or PCM programming.

Can I drive with P0315?

Usually for a short period if the engine runs normally and no serious companion codes are present. Diagnosis is still recommended because misfire monitoring may be inaccurate.

Will P0315 cause a no-start?

P0315 alone usually does not cause a no-start. A no-start condition suggests an additional sensor, circuit, timing, fuel, ignition, or mechanical problem.

Can P0315 cause misfire codes?

Yes. An incorrect or missing variation value can interfere with accurate misfire detection.

Do I need a scan tool to fix P0315?

Many vehicles require an enhanced scan tool capable of initiating the manufacturer’s crankshaft variation relearn. Some applications use an automatic or manufacturer-specific alternative.

Can a basic code reader perform the relearn?

Usually not. Basic readers generally retrieve and clear codes but cannot command service functions.

When is a crankshaft relearn required?

It may be required after crankshaft sensor, PCM, engine, crankshaft, reluctor, flywheel, flexplate, timing, clutch, or certain transmission repairs.

Can disconnecting the battery cause P0315?

On some applications, loss of learned memory may contribute to P0315. This is vehicle-specific.

Why won’t the crankshaft relearn complete?

Common causes include active codes, incorrect engine temperature, unstable voltage, sensor signal problems, reluctor damage, timing errors, actual misfires, or unmet enable conditions.

Is a crankshaft relearn dangerous?

The procedure can involve rapid engine acceleration and high RPM. It must be performed only when the engine is mechanically sound and all safety conditions are satisfied.

Can an aftermarket crankshaft sensor cause P0315?

Yes. An incorrect, incompatible, poorly manufactured, or improperly installed sensor may produce a signal the PCM cannot learn reliably.

Related OBD-II Codes

Explore the Pro Street OBD-II Code Libraries

Use the Pro Street cornerstone pages to find additional diagnostic trouble codes:

P0315 means the PCM has not learned or retained a valid crankshaft position variation value.

Begin by checking recent repair history and scanning for crankshaft sensor, camshaft sensor, timing, voltage, and misfire codes. Inspect the sensor, wiring, reluctor wheel, flywheel or flexplate, and mechanical timing as required.

If no underlying fault remains, complete the manufacturer’s crankshaft variation relearn using a compatible scan tool and the exact safety procedure for the vehicle.

P0315 is often solved with calibration. Replacing the crankshaft sensor repeatedly will not teach the PCM anything, although it may teach the vehicle owner several new vocabulary words.

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