The P0386 OBD-II trouble code means the powertrain control module is receiving a signal from Crankshaft Position Sensor “B,” but that signal falls outside the expected operating range or does not perform as expected.
Unlike P0385, which identifies a general Sensor B circuit malfunction, P0386 usually means a signal exists but its voltage, frequency, pulse spacing, timing or relationship to other engine-position signals is implausible.
A weak sensor can cause P0386, but so can excessive sensor clearance, a damaged reluctor wheel, unstable wiring, low cranking speed, electrical interference or incorrect mechanical timing. Replacing the sensor without examining its waveform can therefore produce the traditional diagnostic result: a new part, the same code and a slightly lighter wallet.
P0386 Quick Reference
| Item | Details |
|---|---|
| Trouble code | P0386 |
| Code definition | Crankshaft Position Sensor “B” Circuit Range/Performance |
| System affected | Engine-position, ignition and fuel-injection control |
| Fault type | Sensor B signal exists but is implausible or outside its expected range |
| Common causes | Weak sensor, excessive air gap, reluctor damage, wiring resistance, electrical noise or mechanical timing problems |
| Common symptoms | Check Engine Light, hard starting, stalling, rough running, misfires or reduced power |
| Typical severity | Moderate to severe |
| Safe to drive? | Not recommended if stalling, hard starting or power loss occurs |
| Repair difficulty | Intermediate to advanced |
What Does the P0386 Code Mean?
P0386 indicates that the PCM has detected a performance problem with the Crankshaft Position Sensor B signal.
The PCM may still receive electrical activity from the sensor, but the resulting waveform does not agree with the calibrated pattern expected for the engine’s speed and position.
Depending on the vehicle, the PCM may set P0386 when it detects:
- Signal amplitude outside the expected range
- Incorrect pulse frequency
- Missing reluctor-wheel pulses
- Additional or false pulses
- Uneven pulse spacing
- A distorted reference gap
- Poor correlation between Sensor A and Sensor B
- Poor correlation between crankshaft and camshaft signals
- A signal that becomes unreliable at certain engine speeds
- Sensor output that is too weak during cranking
- A waveform that does not match the installed engine calibration
The exact code-setting criteria vary by manufacturer. Service information is required to determine whether the PCM is evaluating voltage, frequency, synchronization, pulse count or a combination of those factors.
What Is Crankshaft Position Sensor B?
Crankshaft Position Sensor B is the secondary crankshaft-position input identified by the vehicle manufacturer.
Some engines use two crankshaft-position sensors for:
- Signal redundancy
- Improved position resolution
- Faster engine synchronization
- Misfire detection
- Separate low-speed and high-speed monitoring
- Fail-safe operation
- Comparison between different sections of a reluctor wheel
Sensor B does not automatically mean Bank 2. The crankshaft is shared across the engine, and manufacturers do not use one universal naming system for secondary crankshaft sensors.
Sensor B may be positioned near the:
- Crankshaft pulley
- Timing cover
- Flywheel
- Flexplate
- Transmission bellhousing
- Rear main-seal area
- Engine block
- Internal crankshaft reluctor wheel
Always confirm its identity with the factory wiring diagram and component-location information.
How the Crankshaft-Position Signal Works
The crankshaft-position sensor reads a toothed, slotted or magnetized trigger wheel attached to the crankshaft, flywheel or flexplate.
As the crankshaft rotates, the sensor generates a series of electrical pulses. The PCM uses those pulses to calculate:
- Engine RPM
- Crankshaft angle
- Piston position
- Ignition timing
- Fuel-injection timing
- Engine synchronization
- Misfire activity
- Camshaft-to-crankshaft relationship
A missing tooth, wider slot or other unique feature serves as a reference point. If the pattern becomes distorted, the PCM may still see a signal but no longer trust it. That is the basic territory covered by P0386.
Magnetic and Hall-Effect CKP Sensors
Crankshaft-position sensors generally use one of two designs.
Magnetic or Variable-Reluctance Sensor
A magnetic sensor normally uses two wires and generates an alternating-current waveform as reluctor teeth pass its magnetic tip.
Signal strength is affected by:
- Cranking speed
- Sensor air gap
- Reluctor-tooth condition
- Sensor magnet strength
- Wiring resistance
- Metal debris on the sensor
- Temperature
A magnetic sensor may work at higher engine speeds but produce insufficient voltage during cranking.
Hall-Effect Sensor
A Hall-effect sensor generally uses:
- Power or reference voltage
- Sensor ground
- Digital signal output
It switches the signal between defined high and low states as the trigger wheel rotates.
Hall-effect performance can be affected by:
- Missing reference voltage
- Poor ground
- Incorrect signal bias
- Damaged trigger-wheel magnets
- Excessive air gap
- Internal sensor electronics
- Signal-wire resistance
- Electrical interference
Testing procedures differ between the two designs. A resistance test that may be appropriate for a magnetic pickup is generally not a valid performance test for an active Hall-effect sensor.
Symptoms of a P0386 Code
Possible symptoms include:
- Illuminated Check Engine Light
- Extended cranking
- Intermittent hard starting
- Engine cranks but does not start
- Engine stalls unexpectedly
- Rough idle
- Engine hesitation
- Misfire-like operation
- Reduced engine power
- Poor throttle response
- Unstable tachometer reading
- Incorrect RPM data
- Limp-home mode
- Poor fuel economy
- Difficult hot or cold starting
- Engine that restarts after cooling
- No noticeable driveability symptoms
Symptoms depend on whether the PCM can substitute information from Sensor A or a camshaft-position sensor.
If the engine turns over but never begins running, use the broader engine cranks but won’t start diagnostic guide to check spark, fuel delivery, injector command and engine-position data.
If the failure primarily appears after the engine becomes hot, review why an engine stalls when warm.
Common Causes of P0386
Common potential causes include:
- Weak Crankshaft Position Sensor BInternal electrical or magnetic deterioration may produce an inaccurate waveform without causing complete signal loss.
- Excessive Sensor Air GapToo much clearance between the sensor and reluctor wheel can reduce signal amplitude.
- Incorrect Sensor InstallationDebris beneath the sensor, an incorrect spacer or improper seating can alter the sensor’s operating distance.
- Damaged Reluctor WheelMissing, bent, cracked or corroded reluctor teeth can distort the expected pulse pattern.
- Loose or Shifted Reluctor RingA reluctor that moves relative to the crankshaft can produce incorrect timing even though the sensor remains functional.
- Bent Flywheel or FlexplatePhysical runout can continuously change the sensor air gap and waveform amplitude.
- Metal Debris on the Sensor TipMagnetic sensors may collect metallic debris that interferes with the signal.
- High Resistance in the Signal CircuitCorrosion or damaged terminals may weaken the waveform before it reaches the PCM.
- Poor Sensor GroundA weak ground can distort the high and low states of an active sensor.
- Unstable Reference VoltageA fluctuating supply can create inconsistent Hall-effect sensor output.
- Electrical InterferenceDamaged shielding, incorrect harness routing, ignition noise or alternator interference may introduce false pulses.
- Low Battery Voltage or Slow CrankingReduced cranking speed can produce weak magnetic-sensor output and interfere with engine synchronization.
- Incorrect Replacement SensorA sensor with the wrong depth, waveform characteristics or connector configuration may produce an implausible signal.
- Camshaft or Crankshaft Timing ProblemA stretched chain, jumped belt or incorrectly installed timing component can disrupt expected signal correlation.
- Excessive Crankshaft End PlayCrankshaft movement can change the sensor-to-reluctor clearance.
- PCM Software or Input-Circuit ProblemAn outdated calibration or faulty PCM input may incorrectly interpret an otherwise usable signal.
How Serious Is P0386?
P0386 is a moderate-to-severe trouble code because the PCM depends on accurate crankshaft-position information to control ignition and fuel delivery.
A mildly distorted signal may only illuminate the Check Engine Light. A more serious failure can cause:
- Intermittent stalling
- Extended cranking
- Incorrect ignition timing
- Incorrect injection timing
- Misfire detection problems
- Reduced engine power
- A complete no-start condition
The vehicle should be diagnosed promptly, especially if the engine stalls or becomes difficult to restart. Losing the engine-position signal in traffic is rarely the sort of performance upgrade anyone had in mind.
P0385 vs. P0386
These codes affect the same Sensor B system but describe different fault types.
| Code | Definition | Diagnostic focus |
| P0385 | Crankshaft Position Sensor B Circuit Malfunction | General electrical failure, missing signal, open or shorted circuit |
| P0386 | Crankshaft Position Sensor B Circuit Range/Performance | Signal exists but its pattern, amplitude, timing or frequency is implausible |
P0385 points more strongly toward a basic circuit failure. P0386 requires closer analysis of signal quality and mechanical trigger-wheel condition.
P0386 vs. P0336
P0386 and P0336 are parallel range/performance codes for different crankshaft-position inputs.
| Code | Sensor | Meaning |
| P0336 | Crankshaft Position Sensor A | Sensor A signal outside its expected range or performance |
| P0386 | Crankshaft Position Sensor B | Sensor B signal outside its expected range or performance |
The same general diagnostic principles may apply, but the component location, waveform and circuit specification may differ.
The existing My Pro Street P0336 guides remain useful for their specific applications, including:
Those vehicle-specific procedures should not be applied blindly to an unrelated P0386 system.
P0386 vs. P0315
P0315 means the PCM has not learned the crankshaft-position variation values required for accurate misfire monitoring.
P0386 means the Sensor B signal itself is outside its expected operating range or performance criteria.
A relearn may be required after certain repairs, but performing one will not correct a weak waveform, damaged reluctor or faulty circuit.
P0386 vs. P0321
P0321 identifies a broader engine-speed input range/performance problem.
P0386 specifically identifies the Crankshaft Position Sensor B circuit. Keeping those targets separate prevents the P0386 page from competing for general engine-speed signal searches.
How to Diagnose the P0386 Code
P0386 diagnosis should focus on waveform quality rather than simple signal presence. A digital multimeter is useful for checking power, ground and circuit integrity, but an oscilloscope is the best tool for finding missing pulses, weak amplitude and timing errors.
1. Confirm the Code and Freeze-Frame Data
Connect a capable scan tool and record:
- P0386
- Current, pending and history codes
- Freeze-frame engine speed
- Battery voltage
- Coolant temperature
- Vehicle speed
- Engine load
- Camshaft synchronization
- Crankshaft synchronization
- Misfire data
- Sensor A and Sensor B data, when supported
The freeze-frame conditions may reveal whether the fault occurs during cranking, at idle, at highway speed or only when the engine is hot.
Do not clear the codes until the information has been recorded.
2. Check for Related Trouble Codes
Pay attention to codes involving:
- Crankshaft Position Sensor A
- Crankshaft Position Sensor B
- Camshaft-position sensors
- Crankshaft-to-camshaft correlation
- Sensor reference voltage
- System voltage
- Engine misfires
- PCM communication
- Crankshaft variation relearn
A shared reference-voltage problem may affect several sensors simultaneously. Multiple related codes often provide better direction than P0386 by itself.
3. Verify the Symptoms
Start or crank the engine while monitoring:
- Engine RPM
- Crankshaft synchronization
- Camshaft synchronization
- Sensor A status
- Sensor B status
- Misfire counters
Watch for:
- RPM that drops to zero
- Synchronization that changes intermittently
- Sensor B data that disagrees with Sensor A
- Failure only at certain speeds
- Signal problems after warm-up
- P0386 returning immediately
A zero-RPM reading may suggest complete signal loss, while unstable or implausible RPM more closely supports a performance problem.
4. Identify Sensor B Correctly
Before touching the vehicle, consult service information and identify:
- Sensor B location
- Sensor type
- Connector pinout
- Power-supply voltage
- Ground circuit
- Signal circuit
- Expected waveform
- Specified sensor air gap
- Reluctor-wheel design
- PCM connector terminals
Do not assume Sensor B means Bank 2, the rear sensor or whichever sensor is easiest to reach. Manufacturers remain stubbornly unwilling to standardize the part of the process where guessing would be most convenient.
5. Inspect the Sensor and Harness
Inspect the Sensor B circuit for:
- Oil contamination
- Water intrusion
- Corroded terminals
- Loose terminal tension
- Broken connector locks
- Melted insulation
- Harness contact with exhaust components
- Wiring rubbed against metal brackets
- Damaged shielding
- Improper splices
- Stretched wiring near the transmission
- Metal debris on the sensor tip
A range/performance code can result from high resistance or interference even when the circuit is not completely open.
6. Check Battery and Cranking Voltage
Verify:
- Battery state of charge
- Battery-terminal condition
- Engine ground condition
- Starter current draw
- Minimum cranking voltage
- Cranking speed
- Charging-system voltage
A magnetic crankshaft sensor generates voltage according to reluctor speed. If the starter turns the engine too slowly, the sensor waveform may not reach the amplitude required by the PCM.
Correct low-voltage or cranking-speed problems before evaluating the final sensor waveform.
7. Verify Hall-Effect Sensor Power and Ground
For a three-wire Hall-effect sensor, test:
- Supply or reference voltage
- Ground voltage drop
- Signal bias voltage
- Connector-terminal fit
Compare the readings with factory specifications.
A supply circuit that measures correctly with the sensor disconnected may collapse under load. Back-probe the circuit with the sensor connected whenever the approved procedure allows it.
8. Test a Magnetic Sensor
For a two-wire magnetic sensor:
- Check resistance only against the manufacturer’s specification
- Test for a short between either circuit and ground
- Measure AC voltage during cranking
- Compare the output with Sensor A when possible
- Repeat the test with the sensor hot
Resistance alone cannot evaluate waveform shape, air gap or reluctor condition. A sensor can pass a static resistance test and still produce a signal the PCM cannot use.
9. Capture the Sensor B Waveform
Connect an oscilloscope and capture the waveform during:
- Cranking
- Idle
- Acceleration
- Deceleration
- Warm operation
- The engine speed recorded in freeze-frame data
For a digital Hall-effect sensor, inspect:
- High-state voltage
- Low-state voltage
- Duty cycle
- Pulse width
- Pulse spacing
- Missing or additional pulses
For a magnetic sensor, inspect:
- Peak-to-peak amplitude
- Waveform symmetry
- Pulse spacing
- Reference gap
- Noise
- Changes in amplitude caused by runout
A signal can appear acceptable at idle but fail at higher speeds, under heat or during slow cranking.
10. Compare Sensor A and Sensor B
When both signals are available, display them on separate oscilloscope channels.
Compare:
- Relative timing
- Pulse count
- Amplitude
- Reference gaps
- Signal stability
- Response to RPM changes
An incorrect relationship between otherwise clean waveforms may indicate:
- A shifted reluctor wheel
- Incorrect mechanical timing
- An improperly installed sensor
- The wrong replacement sensor
- Excessive crankshaft movement
- Incorrect PCM calibration
This comparison is often the most efficient way to distinguish an electrical performance fault from a mechanical timing problem.
11. Compare Crankshaft and Camshaft Signals
If Sensor A and Sensor B appear reasonable, compare the crankshaft waveform with the appropriate camshaft-position signal.
Incorrect crank-to-cam correlation can result from:
- A jumped timing chain
- A stretched chain
- Incorrect timing-belt installation
- A damaged camshaft reluctor
- A shifted crankshaft reluctor
- Variable-valve-timing problems
Do not replace Sensor B simply because it reported the disagreement. Sometimes the messenger is functioning perfectly and the engine’s mechanical timing is the part that has wandered off.
12. Check the Sensor Air Gap
Measure the distance between Sensor B and its trigger wheel when the design allows it.
An excessive or inconsistent air gap may result from:
- Debris under the sensor flange
- Incorrect sensor installation
- Wrong sensor dimensions
- Missing or incorrect spacer
- Bent mounting bracket
- Reluctor runout
- Bent flexplate
- Crankshaft end play
Check the waveform while rotating the engine manually if the factory procedure permits it. Repeating amplitude changes may correspond with a bent or eccentric trigger wheel.
13. Inspect the Reluctor Wheel
Look for:
- Missing teeth
- Bent teeth
- Cracks
- Rust buildup
- Foreign material
- A loose retaining key
- A shifted pressed-on ring
- Damage from previous repairs
- A cracked or bent flexplate
Some reluctors are internal and difficult to inspect directly. A consistent waveform defect at the same crankshaft position can identify reluctor damage without immediate disassembly.
14. Check for Electrical Interference
Crankshaft-position signals can be affected by induced voltage from:
- Ignition coils
- Spark-plug wires
- Alternator wiring
- Starter cables
- Fuel-injector circuits
- Poor engine grounds
- Improperly routed aftermarket wiring
Inspect shielding and harness routing. Compare the waveform with major electrical loads switched on and off.
Noise that appears only during starter operation may come from poor battery cables, starter problems or inadequate grounding rather than the sensor.
15. Compare the Signal at the Sensor and PCM
Capture Sensor B at its connector and then at the PCM.
If the waveform is clean at the sensor but distorted at the PCM, inspect the harness for:
- High resistance
- Damaged shielding
- Poor terminal tension
- Shorts between circuits
- Corroded splices
- Electromagnetic interference
If the waveform reaches the PCM correctly, verify PCM powers, grounds, calibration and connector condition before considering module replacement.
16. Perform Heat and Harness Tests
If the fault is intermittent:
- Warm the engine to operating temperature
- Monitor the waveform continuously
- Move the harness carefully
- Tap lightly on the connector where appropriate
- Apply controlled heat according to service procedures
- Cool the suspected component and repeat the test
A waveform that loses amplitude as the sensor heats may indicate internal sensor deterioration. A signal that changes when the harness moves points toward wiring or terminal damage.
17. Consider PCM Software or Failure Last
Before replacing the PCM, confirm:
- Correct Sensor B identification
- Proper power and ground
- Correct air gap
- Clean waveform at the PCM
- Correct reluctor condition
- Proper mechanical timing
- Correct replacement sensor
- No technical service bulletin
- No available calibration update
PCM replacement may require programming, immobilizer initialization and a crankshaft-position variation relearn.
Common P0386 Diagnostic Mistakes
Avoid these common mistakes:
- Treating P0386 as a completely dead sensor circuit
- Replacing Sensor B without viewing its waveform
- Confusing Sensor B with Bank 2
- Ignoring low cranking speed
- Checking resistance but not signal quality
- Missing excessive sensor air gap
- Overlooking a bent flexplate
- Ignoring metal debris on a magnetic sensor
- Failing to compare Sensors A and B
- Ignoring crankshaft-to-camshaft correlation
- Replacing a sensor when the reluctor has shifted
- Installing a low-quality sensor with an incorrect waveform
- Performing a relearn instead of repairing the signal problem
- Blaming the PCM before testing the circuit at its connector
Repairs That May Fix P0386
The correct repair depends on the measured fault.
Possible repairs include:
- Replacing a weak Crankshaft Position Sensor B
- Correcting Sensor B installation
- Correcting excessive sensor air gap
- Cleaning metal debris from the sensor tip
- Repairing high resistance in the signal circuit
- Repairing the sensor power or ground circuit
- Cleaning or replacing connector terminals
- Replacing a damaged connector
- Restoring damaged signal shielding
- Correcting harness routing
- Repairing battery or starter problems
- Replacing a damaged reluctor wheel
- Replacing a bent flywheel or flexplate
- Correcting crankshaft end play
- Repairing mechanical timing
- Installing the correct sensor
- Updating PCM software
- Replacing and programming the PCM after confirmed failure
- Performing a crankshaft-position variation relearn when required after repair
Estimated P0386 Repair Costs
Repair costs depend heavily on sensor accessibility and whether the fault is electrical or mechanical.
| Repair | Estimated cost |
| Diagnostic inspection | $100–$250 |
| Connector or minor wiring repair | $100–$350 |
| Crankshaft Position Sensor B replacement | $180–$650 |
| Battery or cable repair | $150–$600 |
| Starter replacement | $350–$900 |
| Major harness repair | $300–$1,000 |
| Reluctor-wheel or flexplate replacement | $700–$2,500 |
| Timing-chain or timing-belt repair | $800–$3,500 |
| PCM software update | $100–$300 |
| PCM replacement and programming | $800–$2,500 |
An externally mounted sensor may be inexpensive to replace. A damaged internal reluctor wheel can require major engine or transmission disassembly, because sometimes the twenty-dollar signal problem lives behind two thousand dollars of labor.
Can You Drive With P0386?
Driving with P0386 is not recommended if the vehicle has stalling, hard-starting, misfire or reduced-power symptoms.
The vehicle may continue operating if the PCM can rely on Sensor A, but the Sensor B signal may deteriorate without warning.
Stop driving and arrange diagnosis if:
- The engine stalls
- The tachometer drops unexpectedly
- The engine loses power
- Starting becomes unreliable
- The Check Engine Light flashes
- Multiple timing or misfire codes appear
- The engine produces abnormal mechanical noise
For broader warning-light guidance, see what the Check Engine Light means.
How to Verify the Repair
After completing the repair:
- Reconnect all sensors and modules.
- Secure the harness away from heat and moving components.
- Clear current and pending trouble codes.
- Monitor Sensor A and Sensor B during cranking.
- Confirm stable synchronization.
- Compare both waveforms at idle and through the operating range.
- Warm the engine fully.
- Recreate the original freeze-frame conditions.
- Complete the required drive cycle.
- Perform a crankshaft variation relearn if specified.
- Recheck for pending codes.
The repair is complete when Sensor B remains within its specified range, its waveform stays consistent and P0386 does not return.
Frequently Asked Questions
What does the P0386 code mean?
P0386 means the Crankshaft Position Sensor B signal is present but outside the range or performance expected by the PCM.
Does P0386 mean Sensor B has failed?
Not necessarily. The sensor may be weak, but excessive air gap, reluctor damage, wiring resistance, low cranking speed, electrical noise and timing problems can produce the same code.
Is Crankshaft Position Sensor B on Bank 2?
Not necessarily. Sensor B identifies a manufacturer-designated secondary crankshaft-position input. It does not universally mean Bank 2.
What is the difference between P0385 and P0386?
P0385 identifies a general Sensor B circuit malfunction. P0386 indicates that the Sensor B signal exists but its electrical or timing performance is implausible.
What is the difference between P0336 and P0386?
P0336 applies to Crankshaft Position Sensor A. P0386 applies to Crankshaft Position Sensor B.
Can P0386 cause an engine not to start?
Yes. If the PCM cannot accurately determine crankshaft position, it may not provide correct spark or injector operation.
Can a bad reluctor wheel cause P0386?
Yes. Missing teeth, a shifted ring, flexplate runout or reluctor damage can distort the Sensor B waveform.
Can low battery voltage cause P0386?
Low battery voltage can reduce cranking speed and weaken the output of a magnetic crankshaft-position sensor. Battery and starter performance should be checked during diagnosis.
Will a crankshaft relearn fix P0386?
A relearn will not repair a weak or distorted Sensor B signal. It should only be performed when specified after the underlying electrical or mechanical problem has been corrected.
How do you diagnose P0386?
Verify sensor power and ground, inspect the air gap and reluctor, and compare the Sensor B waveform with Sensor A and the relevant camshaft signal.
Final Thoughts
P0386 means Crankshaft Position Sensor B is producing a signal the PCM considers implausible. That distinction matters: this is usually a signal-quality or performance problem, not merely a missing circuit.
Begin with battery condition, sensor identification and connector inspection. Then use an oscilloscope to compare Sensor B with Sensor A and the relevant camshaft signal. That comparison can reveal weak amplitude, missing reluctor pulses, incorrect timing, electrical interference or mechanical damage that a basic resistance test will never show.
Visit the OBD-II Doctor for additional diagnostic guides or browse the complete P-series OBD-II code reference to identify related faults.
