P0389 — Crankshaft Position Sensor B Circuit Intermittent

P0389 — Crankshaft Position Sensor B Circuit Intermittent. A fault in the crankshaft position sensing. Driving is not recommended until fixed. Typical causes: incorrect sensor air gap, damaged reluctor wheel on the crankshaft, failed crankshaft position sensor.

powertrain (engine/transmission)

Is it safe to drive?

Possible stalling or failure to restart P0389 can interrupt the crankshaft-position signal and cause a sudden stall. If the engine runs normally, drive cautiously to a repair facility; if it stalls, loses substantial power, or will not restart, avoid further driving and arrange towing.

Typical symptoms

  • The check-engine light illuminates with P0389 stored in the powertrain controller
  • The engine intermittently cranks without starting or takes an unusually long time to start
  • The engine may stall suddenly or lose power while driving
  • Hesitation, rough idle, or brief tachometer-RPM dropouts may occur as the sensor signal disappears
  • The fault may return more often when the engine is hot or after the vehicle has been driven

Common causes

  • An intermittent open, short, or high-resistance connection in the crankshaft position sensor B signal circuit identified by P0389
  • A loose, corroded, burned, or improperly seated connector pin at the crankshaft position sensor B or engine wiring harness
  • Chafed wiring or a broken solder joint near hot, vibrating, or moving engine components
  • A crankshaft position sensor B with an intermittently failing internal pickup, coil, or Hall element
  • An excessive sensor air gap, damaged reluctor, or missing crankshaft ring-gear tooth causing intermittent loss of position pulses

How to diagnose with an OBD scanner

  1. Confirm P0389 and capture operating data Connect an ELM327, AIScanAuto, or other OBD2 scanner and read stored, pending, and freeze-frame data. Confirm whether P0389 is active or historical, and record engine RPM, battery voltage, coolant temperature, and operating conditions when the fault appears. Also note any crankshaft-related codes such as P0335, P0336, or P0338.
  2. Inspect the sensor B circuit Identify crankshaft position sensor B using the vehicle wiring diagram, then inspect its connector, terminals, sensor body, and harness routing. Look for loose pins, green corrosion, heat damage, oil or coolant contamination, pinching, and chafing near brackets, exhaust components, and moving accessories.
  3. Perform guided electrical tests With the circuit disconnected, use a multimeter to check continuity and unintended shorts while flexing suspect sections. Then verify sensor power and ground according to its design; do not expect a 5-volt reference on a two-wire variable-reluctance sensor. Watch the scan data for P0389 while performing the wiggle test.
  4. Check the crankshaft signal waveform Use an oscilloscope to monitor the sensor B output while cranking and running. Missing pulses, excessive jitter, or a collapsing signal that coincides with P0389 points toward the sensor, wiring, connector, power supply, or poor ground rather than an unrelated engine condition.
  5. Check sensor spacing and reluctor condition Verify sensor mounting, alignment, and air gap against service specifications. Inspect the reluctor or crankshaft ring gear for damaged, cracked, or missing teeth and remove debris that could disturb the magnetic field. Excessive clearance or a damaged reluctor can make the sensor signal intermittent.
  6. Repair and verify the fault Repair the damaged wiring or terminals first, or replace the failed sensor if testing supports that conclusion. Clear P0389 with the scanner, restart the engine, and road-test while watching for its return. Repeat the inspection hot and under vibration if the code remains intermittent.

Approximate repair cost

A typical independent-shop range for diagnosing and repairing P0389 is USD $150-$500, depending on whether the repair involves a connector, harness section, or sensor. Damage to the reluctor or crankshaft ring gear can cost more. Figures are estimates and vary by region.

Common questions

Does P0389 always mean the crankshaft position sensor is defective?

No. P0389 identifies an intermittent crankshaft position sensor B circuit condition, and a damaged wire, poor terminal, bad ground, excessive air gap, or failing sensor can all produce it.

Can I keep driving after clearing P0389?

Clearing the code does not repair the underlying fault. If the engine is running normally, drive only cautiously and seek diagnosis promptly because P0389 can lead to a sudden stall or failure to restart.

Why might P0389 appear only when the engine is warm?

Heat can expand terminals, soften insulation, or expose a marginal connector or damaged wire. A sensor that fails as it heats may also create an intermittent signal and set P0389 only after warm operation.

What does the B circuit mean in P0389?

The B designation identifies the manufacturer-labeled crankshaft position sensor circuit involved. Its connector, pin layout, sensor type, and test procedure vary, so the correct wiring diagram is essential before testing.

The engine control module constantly monitors signals from various sensors to keep the engine running smoothly. When it detects that the crankshaft position sensor B is sending erratic or inconsistent data, it logs trouble code P0389. This specific code points to an intermittent fault in the circuit—the sensor works sometimes but fails at other moments, making diagnosis tricky since the problem may not show up during a quick shop visit.

Crankshaft position sensing is critical for engine timing. The sensor reads notches on a reluctor wheel attached to the crankshaft and sends that information to the ECM, which uses it to calculate RPM and determine injection and ignition timing. Sensor B typically refers to a secondary or backup sensor in systems that use two crankshaft position sensors for redundancy. When the signal drops out or becomes unreliable, the ECM cannot properly time the engine, which triggers P0389 once the fault repeats under specific operating conditions.

The module requires multiple fault detections before illuminating the check engine light and storing the code. It also captures freeze frame data—engine load, RPM, temperature, and vehicle speed at the moment of failure. This snapshot tells you exactly what conditions caused the problem, which is essential for reproducing the fault during testing.

Common Symptoms of P0389

  • Intermittent no-start condition, especially when the engine is warm
  • Tachometer needle stays dead while cranking the starter
  • Engine stalls unexpectedly with little or no warning
  • Cranking without ignition—starter spins the engine but it refuses to start
  • Check Engine Light illuminated on the dashboard

What Causes P0389?

  • Wiring that loses contact due to vibration, heat cycles, or physical movement
  • Broken conductor hidden inside intact wire insulation
  • Connector pin that is loose, corroded, or partially backed out of its housing
  • Incorrect air gap between the sensor tip and reluctor wheel
  • ECM hardware failure or software corruption affecting signal processing
  • Complete failure of the crankshaft position sensor itself
  • Damage to the reluctor wheel teeth or missing segments on the tone ring

How to Diagnose P0389

  1. Connect an OBD2 scanner, verify that P0389 is present, and record all freeze frame data—these parameters show exactly what was happening when the fault occurred.

  2. Look for related diagnostic trouble codes that may point to the root cause. Check manufacturer technical service bulletins for your specific make and model—many sensor issues have known fixes or ECM updates available.

  3. Perform a thorough visual inspection of the crankshaft position sensor wiring harness and connectors. Look for chafing, melted insulation, corrosion, or any signs of loose connections.

  4. Actively try to provoke the fault by wiggling the harness and tapping the sensor while monitoring live data. Heat and vibration often expose intermittent failures that do not appear during static testing.

  5. Check the RPM parameter identification while cranking the engine—absent or frozen readings indicate a problem in the sensor circuit.

  6. Remove and inspect the sensor mounting, check the air gap against factory specifications, and examine the reluctor wheel for damaged teeth, metal debris, or contamination.

  7. Clear the code, drive the vehicle through conditions matching the freeze frame data, and verify that P0389 does not reappear.

Repair Options for P0389

Addressing the most affordable and likely causes first saves money:

  • Replace the crankshaft position sensor: $150–$400
  • Repair or reterminate sensor wiring and connectors: $80–$250
  • Replace the damaged reluctor wheel: $400–$900

How Much Does It Cost to Fix P0389?

The total repair cost depends entirely on which component is actually at fault. Based on typical independent shop labor rates and part prices in the United States, the main repair scenarios for P0389 break down as follows: crankshaft position sensor replacement runs $150–$400, wiring repairs typically cost $80–$250, and reluctor wheel replacement—the most expensive scenario—falls between $400–$900. Most P0389 repairs land somewhere between $80 and $900 total. The key takeaway is to confirm the exact failure point before purchasing parts, since the least expensive fix is almost always the first one to investigate.

Can You Drive with P0389?

Do not drive this vehicle. An intermittent crankshaft position sensor causes sudden engine stall with no advance warning, creating serious hazards in traffic, intersections, or highway driving. The car may also fail to start entirely when the sensor drops out. Schedule repair immediately and use a tow vehicle if necessary.

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