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

Item	Information
Trouble code	P0315
Definition	Crankshaft Position System Variation Not Learned
System	Engine position monitoring and misfire detection
Severity	Moderate
Safe to drive?	Usually briefly if the engine runs normally and no serious companion codes are present
Most common cause	Required crankshaft variation relearn has not been completed
Other causes	Sensor signal fault, reluctor damage, wiring, incorrect installation, or PCM issue
Typical solution	Diagnose related faults and perform the manufacturer’s relearn procedure
Related codes	P0314, P0335–P0339, P0300 and cam/crank correlation codes
Typical repair range	Approximately $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:

Ignition timing
Fuel injection
Engine speed
Cylinder identification
Misfire detection
Variable valve timing
Starting strategy

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:

Normal mechanical variation
Combustion-related crankshaft acceleration
Actual cylinder misfires
Sensor or reluctor irregularities

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:

Code	Meaning
P0315	Crankshaft position variation calibration is missing or invalid
P0335	Crankshaft Position Sensor “A” circuit malfunction
P0336	Crankshaft Position Sensor “A” range or performance fault
P0339	Crankshaft 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:

Warming the engine to operating temperature
Placing the transmission in Park or Neutral
Applying the parking brake
Holding the service brake
Turning accessories off
Using a capable scan tool
Briefly accelerating the engine when commanded
Allowing the PCM to recognize a controlled fuel cutoff
Completing a specified drive cycle

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:

P0315
False misfire detection
P0300
P0314 single-cylinder misfire not identified
Inaccurate cylinder-specific misfire counts
Failed emissions testing
Check Engine Light
Incomplete readiness monitors

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:

Crankshaft position sensor replacement
PCM or ECM replacement
Engine replacement
Crankshaft replacement
Reluctor-wheel replacement
Flywheel replacement
Flexplate replacement
Harmonic balancer service on applicable engines
Timing chain or timing belt repair
Transmission removal
Clutch replacement
Engine block replacement
Major internal engine repair
PCM programming or calibration update
Battery disconnection on certain applications
Loss or corruption of learned PCM memory

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:

Check Engine Light
No noticeable drivability problem
Failed emissions inspection
Misfire codes
Inaccurate misfire counters
Rough idle
Hesitation
Reduced engine power
Hard starting
Intermittent stalling
Extended cranking
Relearn procedure that will not complete

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:

Illuminate the Check Engine Light
Prevent emissions-test completion
Interfere with misfire monitoring
Mask a sensor or reluctor problem
Return after being cleared
Accompany a serious timing or crankshaft signal fault

Stop Driving If:

The engine stalls
The engine will not restart
Mechanical knocking is heard
Timing-chain noise develops
The Check Engine Light flashes
Severe shaking or power loss occurs
Oil pressure is low
The engine overheats

Those conditions indicate a problem beyond an incomplete relearn.

Most Common Causes of P0315

Possible cause	Relative likelihood
Crankshaft variation relearn not completed	Very high
PCM recently replaced or programmed	High
Crankshaft sensor recently replaced	High
Engine, flywheel or flexplate recently serviced	High
Incorrect crankshaft sensor installation	Medium
Damaged crankshaft sensor wiring	Medium
Incorrect sensor air gap	Application dependent
Damaged or loose reluctor wheel	Medium
Flywheel or flexplate damage	Medium
Timing-system problem	Lower
Low battery or charging voltage	Lower
PCM software or memory problem	Lower
Failed PCM	Rare

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:

Stored codes
Pending codes
Permanent codes
Freeze-frame data
Manufacturer-specific codes
Crankshaft variation status
Misfire data
Crankshaft and camshaft synchronization

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

Important freeze-frame information may include:

Engine RPM
Engine load
Vehicle speed
Coolant temperature
Battery voltage
Throttle position
Fuel-system status

Step 2: Ask What Was Recently Repaired

Determine whether P0315 appeared after:

Crankshaft sensor replacement
PCM replacement
PCM programming
Engine replacement
Timing-system repair
Transmission removal
Clutch service
Flywheel or flexplate replacement
Internal engine repair

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:

P0314 — Single-Cylinder Misfire Not Identified
P0300 — Random or Multiple-Cylinder Misfire
P0301–P0312 — Cylinder-specific misfire codes
P0335 — Crankshaft Position Sensor A Circuit
P0336 — Crankshaft Position Sensor Range/Performance
P0337 — Crankshaft Position Sensor Circuit Low
P0338 — Crankshaft Position Sensor Circuit High
P0339 — Crankshaft Position Sensor Circuit Intermittent
P0340–P0349 — Camshaft position sensor codes
P0016–P0019 — Crankshaft/camshaft correlation codes
Low-voltage or communication codes

Companion codes determine whether a relearn should be attempted.

Code combination	Diagnostic direction
P0315 only after sensor or PCM work	Verify prerequisites and perform relearn
P0315 plus P0335	Diagnose the crankshaft sensor circuit first
P0315 plus P0336	Inspect signal quality, air gap and reluctor wheel
P0315 plus P0016	Inspect mechanical timing and cam/crank correlation
P0315 plus P0300	Confirm that no active combustion fault exists
P0315 plus low-voltage codes	Test 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:

Battery condition
Battery terminals
Engine grounds
Chassis grounds
Alternator output
PCM power and ground circuits

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:

Correct part number
Correct sensor type
Proper mounting
Correct orientation
Proper connector engagement
No damaged terminals
No pinched O-ring
Correct air gap where applicable
No debris on the sensor tip
No contact with the reluctor wheel

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:

Open circuits
Shorts to ground
Shorts to voltage
Chafed insulation
Oil contamination
Heat damage
Corroded terminals
Loose terminal tension
Poor shielding
Incorrect routing near ignition components

Use wiring diagrams and manufacturer specifications.

Depending on the sensor design, testing may include:

Reference voltage
Ground integrity
Signal voltage
Resistance
Frequency
Duty cycle
Oscilloscope waveform

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:

Bent reluctor tooth
Missing tooth
Cracked wheel
Loose reluctor
Incorrect installation
Wrong reluctor for the engine
Debris on a magnetic sensor
Excessive crankshaft end play
Damage during transmission or engine service

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:

Cracks
Bent sections
Damaged teeth
Incorrect installation
Wrong replacement part
Loose mounting bolts
Excessive runout
Damage after transmission work

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:

Timing chain or belt alignment
Tensioner operation
Timing guides
Camshaft phasers
Camshaft position data
Cam/crank correlation
Engine oil level and pressure

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:

Individual-cylinder misfire counters
Mode $06 misfire data
Fuel trims
Ignition operation
Injector operation
Compression
Engine mechanical condition

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:

No active crankshaft sensor codes
No active camshaft sensor codes
No serious misfire codes
No timing-correlation codes
Stable battery voltage
Engine at operating temperature
Transmission in Park or Neutral
Parking brake applied
Service brake applied
Wheels securely blocked
Air conditioning turned off
Electrical accessories turned off
Power steering not loaded
Vehicle stationary
Correct coolant temperature
Correct transmission temperature
Closed-loop fuel operation
Scan tool communicating reliably

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:

Verify the engine has the correct oil level.
Confirm oil pressure is normal.
Confirm coolant level is correct.
Verify the engine is not overheating.
Repair mechanical noises.
Keep people and tools away from moving components.
Place the vehicle in Park or Neutral as specified.
Apply the parking brake.
Hold the service brake when required.
Block the wheels.
Perform the procedure in a ventilated area.
Follow the scan-tool prompts exactly.

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:

Connect a compatible enhanced scan tool.
Verify that P0315 and related codes have been recorded.
Repair active sensor, timing, voltage, or misfire faults.
Warm the engine to the specified temperature.
Turn off accessories.
Apply the parking brake.
Hold the service brake if instructed.
Select the crankshaft variation relearn function.
Follow all scan-tool prompts.
Accelerate the engine only when commanded.
Release the accelerator immediately when instructed.
Allow the engine to return to idle.
Confirm that the scan tool reports a successful relearn.
Clear codes if instructed.
Complete the required drive cycle.
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:

Clear P0315 if the scan tool does not clear it automatically.
Restart the engine.
Verify that the code does not return.
Monitor misfire counters.
Complete the manufacturer’s drive cycle.
Confirm readiness monitor status.

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:

Engine temperature
Transmission position
Brake-switch status
Parking-brake status
Battery voltage
Accessory loads
Stored companion codes
Scan-tool compatibility
PCM software level
Vehicle speed input
Throttle position
Coolant-temperature data

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:

Active engine misfire
Incorrect sensor installation
Weak or distorted sensor signal
Damaged reluctor wheel
Incorrect flywheel or flexplate
Unstable voltage
Incorrect mechanical timing
Excessive crankshaft end play
Incompatible sensor
PCM software issue
Internal engine problem

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:

P0300
P0301–P0312
P0314

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

Repair	Approximate 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

P0314 — Single-Cylinder Misfire Not Identified
P0315 — Crankshaft Position System Variation Not Learned
P0335 — Crankshaft Position Sensor A Circuit
P0336 — Crankshaft Position Sensor A Range/Performance
P0337 — Crankshaft Position Sensor A Circuit Low
P0338 — Crankshaft Position Sensor A Circuit High
P0339 — Crankshaft Position Sensor A Circuit Intermittent
P0300 — Random or Multiple-Cylinder Misfire
P0301–P0312 — Cylinder-Specific Misfire Codes
P0016–P0019 — Crankshaft/Camshaft Correlation Codes
P0340–P0349 — Camshaft Position Sensor 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.

P0315 Code: Crankshaft Position System Variation Not Learned