Quick answer: The P0389 code indicates that your vehicle’s engine control module detected an erratic or intermittent signal from the Crankshaft Position Sensor “B” circuit. This directly impacts engine timing and ignition performance. It requires prompt attention, as it can cause sudden engine stalling or a complete no-start condition while driving.
Seeing a check engine light triggered by code P0389 can be alarming, especially if your vehicle stumbles or stalls while driving. This diagnostic code signals an issue with how your engine tracks its rotational speed and position. In this guide, we will break down what causes this signal loss, what symptoms to watch for, and how to fix the issue step by step.
What Does P0389 Mean?
The engine control module (ECM) relies on the crankshaft position sensor to know the exact speed and position of the crankshaft. This information allows the computer to time fuel injection and spark plug ignition with millisecond precision. Code P0389 points specifically to the “B” circuit of this system-either a secondary crankshaft sensor or a specific signal track-and indicates that the voltage output from this circuit is intermittent, dropping in and out unpredictably. Because the computer loses track of engine timing whenever the signal drops, it cannot maintain proper combustion.
Symptoms
- Check engine light turns on or flashes during acceleration
- Engine stalls intermittently while idling or driving
- Engine cranks for a long time before starting, or fails to start entirely
- Hesitation, jerking, or misfiring during speed changes
- Unstable, rough idling
- Noticeable drop in overall engine power
Possible Causes
The most common mistake when troubleshooting P0389 is replacing the sensor immediately without checking for loose wiring, corroded connectors, or oil contamination first.
- Damaged, melted, or corroded wiring in the crankshaft sensor “B” circuit
- A loose, oil-soaked, or corroded electrical connector at the sensor
- Faulty or failing Crankshaft Position Sensor “B”
- Debris, metal shavings, or engine oil coating the magnetic tip of the sensor
- Damaged, chipped, or misaligned tone ring (reluctor wheel) inside the engine
- Low battery voltage causing electrical interference across sensor circuits
Check These Yourself Before Visiting a Mechanic
- Inspect the connector: Unplug the sensor “B” wiring connector and look for green corrosion on the pins, broken plastic locking tabs, or oil contamination inside the plug.
- Check for wire damage: Trace the sensor harness back toward the main wiring loom to ensure it has not rubbed against hot exhaust components or sharp engine brackets.
- Check battery condition: Make sure your battery terminals are tight and free of heavy corrosion, as unstable system voltage can trigger false intermittent circuit codes.
How to Fix It
- Connect a professional scan tool to verify code P0389 and check for related codes like P0335 or P0385.
- Perform a visual inspection of the sensor harness, repair any frayed wires, and securely reconnect the electrical plug.
- Test for reference voltage, ground, and signal continuity at the sensor harness connector using a digital multimeter.
- Remove the sensor to clean any metal debris or heavy oil buildup off the sensor face.
- Inspect the reluctor wheel teeth through the sensor mounting hole for bends, missing teeth, or damage.
- Replace the crankshaft position sensor if resistance and output voltage tests fall outside manufacturer specifications.
- Clear all diagnostic codes from the ECM memory and take the vehicle on a test drive to verify the repair.
Estimated Repair Costs (2026)
| Job | Parts ($) | Labor ($) |
|---|---|---|
| Diagnostic Fee | $0 | $80 – $150 |
| Wiring / Connector Repair | $15 – $45 | $75 – $130 |
| Crankshaft Sensor Replacement | $40 – $120 | $90 – $170 |
| Tone Ring / Reluctor Wheel Repair | $60 – $180 | $350 – $700 |
Note: These are 2026 estimates in US dollars; costs vary by make and model.
Frequently Asked Questions
Can I drive with the P0389 code?
Driving with this code is not recommended. Because the signal is intermittent, your engine can stall unexpectedly in heavy traffic or at highway speeds, creating a dangerous situation and leaving you stranded.
How do I clear the P0389 code?
You can clear the code using an OBD-II scanner once the root problem is repaired. If you erase the code without fixing the wiring or sensor issue, the engine computer will log the error and turn the check engine light back on within a few miles.
Can a dying battery cause a P0389 code?
Yes. Low system voltage during engine cranking can disrupt sensitive sensor signals, leading the ECM to record an intermittent circuit fault even if the sensor itself is functioning correctly.