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P0389 Code: Crankshaft Position Sensor “B” Circuit Intermittent

P0389 code indicates intermittent loss of the Crankshaft Position Sensor B signal. Diagnose heat-sensitive sensors, loose terminals and broken wiring.

The P0389 OBD-II trouble code means the powertrain control module has detected an intermittent loss or interruption in the Crankshaft Position Sensor “B” circuit.

Unlike a circuit that remains consistently low or high, the P0389 fault comes and goes. Sensor B may produce a normal signal for several minutes and then drop out because of heat, vibration, moisture, loose connector terminals or a broken wire hidden beneath intact insulation.

A failing sensor is possible, but P0389 should never be diagnosed by replacing the sensor and hoping the intermittent problem becomes someone else’s problem. Intermittent faults require reproducing the failure while monitoring the circuit.

Crankshaft Position Sensor B also does not automatically mean Bank 2. It identifies the manufacturer-designated secondary crankshaft-position input.

P0389 Quick Reference

ItemDetails
Trouble codeP0389
Code definitionCrankshaft Position Sensor “B” Circuit Intermittent
System affectedEngine-position, ignition and fuel-injection control
Fault typeTemporary Sensor B signal dropout or circuit interruption
Common causesHeat-sensitive sensor, loose terminal, broken wire, moisture, poor ground or damaged reluctor
Common symptomsIntermittent stalling, hard starting, no-start after warm-up, hesitation or tachometer dropout
Typical severityModerate to severe
Safe to drive?Not recommended if the engine stalls unpredictably
Repair difficultyAdvanced intermittent electrical diagnosis

What Does the P0389 Code Mean?

P0389 indicates that the PCM temporarily lost the Crankshaft Position Sensor B signal or detected a signal that became electrically unstable.

The signal may:

The PCM depends on crankshaft-position information to determine:

If Sensor B disappears unexpectedly, the PCM may temporarily lose the information required to control spark and injector operation accurately.

What Is Crankshaft Position Sensor B?

Crankshaft Position Sensor B is a secondary crankshaft-position input used on certain engines.

Manufacturers may use a second CKP sensor for:

Sensor B may be installed near the:

Sensor B does not universally indicate Bank 2, the rear sensor or one particular side of the engine. Confirm its location using the manufacturer’s wiring diagram and component-location information.

How the Crankshaft-Position Signal Works

A crankshaft-position sensor monitors a toothed, slotted or magnetized trigger wheel connected to the crankshaft, flywheel or flexplate.

As the crankshaft rotates, the sensor generates a series of electrical pulses. The PCM counts these pulses and uses a missing tooth, reference gap or special magnetic segment to calculate exact crankshaft position.

Two common sensor types are used.

Hall-Effect Sensor

A Hall-effect sensor usually has three circuits:

The signal switches between defined high and low voltage states as the trigger wheel passes the sensor.

An intermittent Hall-effect signal can result from:

Magnetic or Variable-Reluctance Sensor

A magnetic sensor normally uses two wires and generates an alternating-current waveform.

Its output is affected by:

A cracked internal winding may open when hot and reconnect after cooling. The sensor can test perfectly in the driveway and fail fifteen minutes later—which is the automotive version of plausible deniability.

Symptoms of a P0389 Code

Possible symptoms include:

Symptoms depend on whether the PCM can continue operating using Crankshaft Position Sensor A or another engine-position input.

If the starter turns the engine but it will not run, use the engine cranks but won’t start diagnostic guide to check spark, fuel delivery, injector command and engine-position data.

If the engine shuts off primarily after reaching operating temperature, review why an engine stalls when warm.

Common Causes of P0389

Potential causes include:

  1. Heat-Sensitive Crankshaft Position Sensor BInternal sensor electronics or windings may fail as temperature rises and recover after cooling.
  2. Loose Connector TerminalA spread, bent or pushed-back terminal may lose contact during vibration.
  3. Broken Wire Beneath Intact InsulationA conductor may be fractured internally while its outer insulation still appears normal.
  4. Harness Damage Near the Engine or TransmissionHeat, movement and prior repair work can stretch or damage Sensor B wiring.
  5. Oil or Water IntrusionFluid inside the connector can temporarily interrupt or distort the signal.
  6. Corroded Connector TerminalsCorrosion may create unstable resistance that changes with heat and vibration.
  7. Intermittent Sensor GroundA weak ground splice or loose terminal can interrupt a Hall-effect sensor.
  8. Intermittent Reference VoltageA shared sensor-supply circuit may drop out when another sensor or wire temporarily shorts.
  9. Signal Wire Intermittently Shorting to GroundHarness movement may allow damaged insulation to contact the engine or chassis.
  10. Signal Wire Intermittently Shorting to VoltageThe signal conductor may contact a powered wire only when the harness shifts.
  11. Incorrect Sensor Air GapExcessive or changing clearance can cause temporary signal loss.
  12. Bent Flywheel or FlexplateRunout may move the reluctor outside the sensor’s effective range during part of each revolution.
  13. Loose or Shifted Reluctor WheelA reluctor that moves relative to the crankshaft can produce irregular signal timing.
  14. Metal Debris on a Magnetic SensorDebris can weaken or distort the generated waveform.
  15. Excessive Crankshaft End PlayCrankshaft movement can change the sensor air gap under different loads.
  16. Poor Battery or Engine GroundVoltage instability during cranking may temporarily interrupt PCM or sensor operation.
  17. Electromagnetic InterferenceDamaged shielding or incorrect harness routing can introduce ignition, starter or alternator noise.
  18. PCM Connector ProblemLoose or corroded PCM terminals may intermittently interrupt the Sensor B input.
  19. PCM Input-Circuit FailureAn internal PCM fault is possible but should only be considered after proving the external circuit is good.

How Serious Is P0389?

P0389 is a moderate-to-severe trouble code because the engine may stall without warning.

The vehicle might operate normally between failures, but an intermittent crankshaft-position signal can cause:

A vehicle that stalls in traffic should not be driven until the fault is diagnosed.

Intermittent does not mean unimportant. It usually means the failure is waiting for the exact moment when roadside assistance will be most inconvenient.

P0385 Through P0389 Compared

These codes cover different Sensor B circuit conditions.

CodeDefinitionPrimary diagnostic focus
P0385Sensor B Circuit MalfunctionGeneral circuit failure or missing signal
P0386Sensor B Circuit Range/PerformanceImplausible amplitude, timing, frequency or pulse pattern
P0387Sensor B Circuit Low InputSignal consistently below the expected range
P0388Sensor B Circuit High InputSignal consistently above the expected range
P0389Sensor B Circuit IntermittentTemporary dropouts or unstable circuit operation

P0389 should remain focused on a signal that comes and goes rather than one that stays continuously low or high.

P0389 vs. P0339

P0339 is the corresponding intermittent code for Crankshaft Position Sensor A.

CodeSensorFault
P0339Crankshaft Position Sensor ACircuit intermittent
P0389Crankshaft Position Sensor BCircuit intermittent

Do not assume the two sensors share the same location, part number or circuit design.

P0389 vs. P0323

P0323 applies to an intermittent ignition/distributor engine-speed input circuit.

P0389 specifically identifies Crankshaft Position Sensor B. Keeping these pages separated preserves their individual code and circuit intent.

How to Diagnose the P0389 Code

Intermittent faults require capturing the circuit while it fails. A static resistance test performed while the engine is running normally may show nothing wrong.

A scan tool with graphing capability and a multi-channel oscilloscope are the most useful tools.

1. Confirm the Stored Code

Connect a capable scan tool and record:

Determine whether the code was stored:

Do not clear the codes until this information has been recorded.

2. Check for Related Codes

Look for codes involving:

If several sensors lose their signals simultaneously, investigate shared power, ground or PCM circuits.

3. Review the Failure Pattern

Ask when the problem occurs:

A repeatable operating condition provides the best chance of capturing the fault.

4. Identify Sensor B Correctly

Use factory service information to identify:

Do not assume Sensor B is located on Bank 2. It identifies a secondary crankshaft-position input, not a cylinder bank.

5. Inspect the Sensor Connector

Disconnect Sensor B and inspect:

Gently pull each wire from behind the connector. A broken conductor may stretch while the insulation remains attached.

Use the correct terminal-drag tool to evaluate terminal tension. Do not force an oversized meter probe into the connector and create the intermittent connection you were trying to find.

6. Inspect the Wiring Harness

Follow the Sensor B wiring as far as possible.

Pay particular attention to:

Look for insulation that is:

Move the harness while monitoring circuit resistance or waveform activity.

7. Check Battery, Grounds and Charging Voltage

Test:

A loose ground or unstable alternator output can interrupt sensor and PCM operation.

If multiple electrical symptoms occur simultaneously, repair the main power or ground problem before replacing Sensor B.

8. Monitor Scan-Tool RPM

Graph engine RPM while reproducing the failure.

Watch for:

A sudden RPM dropout helps confirm that the failure affects the engine-position input rather than fuel pressure or ignition output alone.

9. Capture the Sensor B Waveform

Connect an oscilloscope and record the waveform during:

For a Hall-effect sensor, watch for:

For a magnetic sensor, watch for:

Use the oscilloscope’s recording or glitch-capture feature when available. An intermittent dropout may last only milliseconds.

10. Compare Sensor A and Sensor B

Display Sensor A and Sensor B simultaneously.

If Sensor A remains stable while Sensor B drops out, concentrate on:

If both signals disappear together, investigate shared:

11. Compare the Signal at the Sensor and PCM

Monitor Sensor B at its connector and then at the PCM.

Possible findings include:

A dual-channel test at both ends of the same circuit can identify exactly where the signal is lost.

12. Perform a Harness Wiggle Test

While monitoring the waveform, move sections of the harness carefully.

Pay attention to changes when moving wiring near:

Do not pull aggressively on a running engine’s wiring near belts, fans or exhaust components.

If waveform loss consistently follows movement in one area, inspect that section closely for broken conductors or terminal problems.

13. Test for Heat-Related Failure

If the engine stalls when warm:

  1. Monitor the Sensor B waveform from cold start.
  2. Record sensor temperature or engine coolant temperature.
  3. Observe the signal as the engine heats.
  4. Apply controlled heat only according to approved procedures.
  5. Cool the sensor and repeat the test.

A sensor that fails at a repeatable temperature and recovers when cooled is a strong candidate for replacement.

Do not use an open flame. The goal is to find a heat-sensitive circuit, not create a new one with melted insulation.

14. Test Hall-Effect Power and Ground During the Failure

For a three-wire Hall-effect sensor, monitor:

Use multiple oscilloscope channels when possible.

If the signal disappears while power and ground remain stable, the sensor or trigger relationship is suspect.

If supply voltage drops simultaneously, inspect the shared reference circuit.

If ground voltage rises, repair the ground circuit.

15. Test a Magnetic Sensor

For a two-wire magnetic sensor:

A cracked winding may open as it expands with heat and reconnect as it cools.

16. Check for Intermittent Shorts

With the sensor and PCM disconnected according to service information, test the signal circuit for intermittent continuity to:

Move the harness throughout the test.

A meter with minimum/maximum capture can record a brief short or open that disappears before the display is noticed.

17. Inspect the Reluctor Wheel and Air Gap

If the electrical circuit remains stable, inspect:

A bent flexplate can change the sensor clearance as it rotates. Excessive end play may move the crankshaft and reluctor away from the sensor under certain loads.

18. Check for Electrical Interference

Inspect the Sensor B circuit for interference from:

Damaged shielding or incorrect harness routing can introduce false pulses or signal dropouts.

Compare the waveform with major electrical loads switched on and off.

19. Consider the PCM Last

PCM failure should only be considered after confirming:

PCM replacement may require programming, security initialization and crankshaft-position variation relearn.

Common P0389 Diagnostic Mistakes

Avoid these common mistakes:

Repairs That May Fix P0389

Possible repairs include:

Estimated P0389 Repair Costs

Actual costs depend on the vehicle, sensor location and time required to reproduce the intermittent fault.

RepairEstimated cost
Diagnostic inspection$120–$300
Connector or terminal repair$100–$400
Crankshaft Position Sensor B replacement$180–$650
Minor harness repair$150–$500
Major harness repair$400–$1,200
Battery cable or ground repair$150–$600
Reluctor-wheel or flexplate repair$700–$2,500
PCM software update$100–$300
PCM replacement and programming$800–$2,500

Intermittent electrical diagnosis may require more labor than replacing the eventual failed component. Finding a broken wire that fails for half a second every twenty minutes tends to consume more time than the repair itself. Electricity remains committed to the bit.

Can You Drive With P0389?

Driving with P0389 is not recommended if the engine stalls unpredictably.

The vehicle may run normally between failures, but the Sensor B signal can disappear again without warning.

Stop driving if:

Review what the Check Engine Light means for additional warning-light guidance.

How to Verify the Repair

After completing the repair:

  1. Reconnect every sensor and module.
  2. Confirm proper terminal engagement.
  3. Secure the harness away from heat and moving parts.
  4. Clear current and pending codes.
  5. Monitor Sensor B during cold cranking.
  6. Warm the engine fully.
  7. Compare Sensor A and Sensor B waveforms.
  8. Repeat the harness wiggle test.
  9. Recreate the original freeze-frame conditions.
  10. Operate the vehicle over the type of surface that previously triggered the failure.
  11. Complete the required drive cycle.
  12. Perform a crankshaft-position relearn if specified.
  13. Recheck for pending codes.

The repair is confirmed when the Sensor B waveform remains stable through temperature, vibration and engine-speed changes and P0389 does not return.

Frequently Asked Questions

What does the P0389 code mean?

P0389 means the PCM detected an intermittent interruption or temporary loss of the Crankshaft Position Sensor B signal.

Does P0389 mean Crankshaft Position Sensor B is bad?

Not necessarily. The sensor may fail when hot, but loose terminals, broken wires, unstable power, poor ground and reluctor problems can cause the same code.

Is Crankshaft Position Sensor B located on Bank 2?

Not necessarily. Sensor B identifies a manufacturer-designated secondary crankshaft-position input and does not universally correspond to Bank 2.

What is the difference between P0385 and P0389?

P0385 identifies a general Sensor B circuit malfunction. P0389 specifically indicates that the Sensor B signal fails intermittently.

What is the difference between P0388 and P0389?

P0388 means the signal remains consistently too high. P0389 means the signal temporarily drops out or becomes unstable.

Can P0389 cause the engine to stall?

Yes. Temporary loss of crankshaft-position information can interrupt ignition and fuel-injection control.

Why does the engine restart after cooling?

An internally damaged sensor or connector may fail as it heats and recover as it cools.

Can a broken wire look normal?

Yes. The copper conductor can break beneath intact insulation, causing a connection that fails only when the harness moves.

How do you diagnose P0389?

Monitor Sensor B with an oscilloscope while reproducing the failure. Perform heat, vibration and harness tests while watching the sensor’s power, ground and signal.

Can a damaged reluctor wheel cause P0389?

Yes. A loose reluctor, bent flexplate or changing sensor air gap can produce temporary signal loss.

Final Thoughts

P0389 means the Crankshaft Position Sensor B signal is disappearing or becoming unstable intermittently. The key to diagnosing it is capturing the circuit during the failure.

Monitor Sensor B power, ground and signal at the same time. Reproduce the operating temperature, vibration, engine speed or road condition that originally stored the code. Comparing Sensor A and Sensor B waveforms can then separate a Sensor B circuit failure from a broader PCM, voltage or mechanical problem.

Replacing the sensor may solve the fault, but evidence should lead to that repair. Intermittent codes already waste enough time without adding guesswork voluntarily.

Visit the OBD-II Doctor for more diagnostic guides or browse the complete P-series OBD-II code reference to identify related powertrain faults.

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