P0389 – Crankshaft Position Sensor “B” Circuit Intermittent

P0389 is an OBD-II trouble code that points to a problem with the crankshaft position sensor “B” circuit, usually on Bank 2 or a secondary sensor. When this code sets, your engine computer is telling you it’s not happy with the signal that helps control ignition timing and fuel injection. You might notice hard starting, rough running, or even stalling. In some cases, the engine won’t start at all. Understanding what P0389 means, how it behaves, and how to fix it will save you time, money, and headaches at the shop.

What Does P0389 Mean?

P0389 stands for “Crankshaft Position Sensor ‘B’ Circuit Intermittent.” The crankshaft position (CKP) sensor tells the ECU where the crankshaft is in its rotation. The “B” usually refers to a secondary sensor or a specific sensor position, often on Bank 2 or a different pickup on the same crank.

When the ECU sees an intermittent, weak, or missing signal from the CKP sensor B circuit, it can’t accurately control spark timing and fuel injection. That’s when it stores P0389 and usually turns on the check engine light.

Quick Reference

  • Code: P0389
  • Definition: Crankshaft Position Sensor “B” Circuit Intermittent
  • Severity: Moderate to high (can cause no-start)
  • Common Causes: Bad CKP sensor, wiring faults, connector issues, damaged reluctor ring
  • Typical Fixes: Replace CKP sensor, repair wiring, clean/secure connectors, inspect tone ring

Real-World Example / Field Notes

In the shop, I often see P0389 on higher-mileage vehicles that start fine when cold but act up once hot. A common pattern: you drive 20–30 minutes, shut the engine off, then it cranks but won’t restart until it cools down. Scan shows P0389 stored or pending. In many of those cases, the crank sensor B was breaking down with heat. Replacing the sensor and cleaning the connector terminals fixed the issue, but I always verify wiring and sensor power/ground before just throwing parts at it.

Symptoms of P0389

  • Check engine light illuminated, sometimes with other misfire or sensor codes
  • Hard starting, especially when the engine is hot or after a short shutdown
  • No-start condition where the engine cranks but will not fire
  • Rough idle or unstable RPM, sometimes feeling like it might stall
  • Engine stalling while driving, often at low speeds or coming to a stop
  • Hesitation or loss of power under acceleration due to erratic timing
  • Poor fuel economy from incorrect ignition timing and fuel delivery
  • Intermittent drivability issues that come and go with temperature or vibration

Common Causes of P0389

Most Common Causes

  • Failed crankshaft position sensor B: Internal sensor failure is very common, especially from heat and age. The sensor may work when cold and fail when hot, creating an intermittent signal.
  • Damaged or corroded connector: Loose pins, corrosion, or moisture in the CKP sensor connector can disrupt the signal and trigger P0389.
  • Wiring issues in the CKP circuit: Chafed, broken, or oil-soaked wiring between the sensor and ECU can cause intermittent voltage or signal dropouts.
  • Improper sensor air gap: If the sensor is not mounted at the correct distance from the reluctor (tone) ring, the signal can be weak or inconsistent.
  • Aftermarket or low-quality sensor: Cheap replacement sensors often produce poor signal quality and can quickly set P0389 again.

Less Common Causes

  • Damaged reluctor/tone ring: Cracked, bent, or missing teeth on the crankshaft tone ring can cause irregular CKP signals.
  • Oil contamination inside sensor area: Excessive sludge or metal debris on a magnetic sensor tip can distort the signal.
  • ECU (PCM) internal fault: Rare, but a failing ECU can misread a good sensor signal and set a false P0389.
  • Incorrect timing components: After engine rebuilds or timing chain/belt work, misaligned components can cause the ECU to see an abnormal crank signal.
  • Poor engine grounds or power supply: Weak grounds or unstable voltage can affect sensor reference and cause intermittent readings.

Diagnosis: Step-by-Step Guide

You’ll want a basic tool set, a good scan tool (preferably with live data and Mode $06), a digital multimeter, and access to wiring diagrams for your specific vehicle. An oscilloscope is ideal, but most DIYers can get pretty far without one.

  1. Confirm the code: Use a scan tool to verify P0389 is present. Check for related codes (like other crank or cam sensor codes) that might point to a bigger issue.
  2. Check freeze-frame data: Look at engine RPM, temperature, and speed when the code set. If it happens hot or at specific RPM, that’s a clue toward a heat-related sensor failure.
  3. Visual inspection: Locate the crankshaft position sensor B. Inspect the wiring harness and connector for damage, rubbing, oil saturation, or corrosion. Repair obvious issues first.
  4. Check connector integrity: Unplug the sensor and inspect the terminals. Look for bent pins, green corrosion, or loose fit. Clean with proper electrical contact cleaner and ensure a snug connection.
  5. Test sensor power and ground: With the key on, use a multimeter to verify you have proper reference voltage (often 5V) and good ground at the connector, following your wiring diagram.
  6. Measure sensor resistance: With the sensor unplugged, measure its resistance and compare to factory specs. An open circuit, short, or wildly out-of-spec reading indicates a bad sensor.
  7. Check live data: On your scan tool, watch engine RPM while cranking. If RPM stays at zero, the ECU isn’t seeing a crank signal. Some scan tools will show individual CKP sensor status or signal quality.
  8. Inspect tone ring and mounting: If accessible, inspect the reluctor ring for missing teeth, cracks, or heavy debris buildup. Verify the sensor is mounted securely and at the correct depth.
  9. Wiggle test: With the engine idling (if it runs), gently wiggle the harness and connector to the CKP sensor B. If the engine stumbles or the RPM reading drops, you likely have a wiring or connector fault.
  10. Advanced testing (if needed): A shop with an oscilloscope can view the actual waveform from the sensor to confirm intermittent dropouts or noise in the signal.

Pro tip: If you replace the CKP sensor, always clear the codes and perform a proper road test. Some vehicles also require a crankshaft position relearn procedure using a scan tool so the ECU can adapt to the new sensor signal.

Possible Fixes & Repair Costs

Typical repairs for P0389 include replacing the crankshaft position sensor B, repairing or replacing damaged wiring, cleaning and tightening connectors, and, in some cases, addressing a damaged reluctor ring or ECU issue. At an independent shop, you’re usually looking at around $120–$350 for a sensor replacement (parts and labor), $100–$250 for wiring repairs, and significantly more if a tone ring or ECU needs replacement. Costs vary based on vehicle make, labor rates in your area, and how difficult the sensor is to access.

Can I Still Drive With P0389?

Sometimes you can drive with P0389 for a short period, but it’s risky. If the sensor signal cuts out completely while driving, the engine can stall without warning, which is dangerous in traffic. You might also experience hard starting or a no-start situation at the worst possible time, like at a gas station or in a parking lot. If the vehicle is running, drive it gently and get it diagnosed as soon as you can. If it’s already stalling or failing to restart, have it towed.

What Happens If You Ignore P0389?

Ignoring P0389 can leave you stranded with a no-start, cause repeated stalling, and potentially stress other components like the starter and battery from constant cranking. Over time, misfires and poor combustion can foul spark plugs and increase fuel consumption. It’s not a code to leave alone for long.

Need wiring diagrams and factory-style repair steps?

Powertrain faults often require exact wiring diagrams, connector pinouts, and guided test steps. A repair manual can help you confirm the cause before replacing parts.

Factory repair manual access for P0389

Check repair manual access

Compare nearby sensor crankshaft trouble codes with similar definitions, fault patterns, and diagnostic paths.

  • P0339 – Crankshaft Position Sensor “A” Circuit Intermittent
  • P0394 – Camshaft Position Sensor “B” Circuit Intermittent Bank 2
  • P0369 – Camshaft Position Sensor “B” Circuit Intermittent Bank 1
  • P0809 – Clutch Position Sensor Circuit Intermittent
  • P2965 – Intake Air Metering Control Valve Position Sensor Circuit Intermittent
  • P0334 – Knock Sensor 2 Circuit Input Intermittent Bank 2

Key Takeaways

  • P0389 means the ECU is seeing an intermittent problem with the crankshaft position sensor B circuit.
  • Common symptoms include hard starting, stalling, rough running, and sometimes a complete no-start.
  • The most frequent causes are a failing CKP sensor, wiring or connector problems, and improper sensor gap.
  • Diagnosis should include visual inspection, voltage and resistance checks, and scan tool data review.
  • Repairs are usually affordable if handled early, but ignoring the code can leave you stranded and cause further issues.

Vehicles Commonly Affected by P0389

P0389 shows up on a wide range of OBD-II vehicles, but it’s especially common on some GM trucks and SUVs, certain BMW and Mercedes-Benz models with dual crank sensors, and various Hyundai and Kia engines. You’ll also see it on some Honda, Acura, and Toyota V6 engines that use multiple crank or cam sensors for precise timing control. High-mileage vehicles, or those exposed to a lot of heat and oil leaks around the bellhousing or crank pulley area, tend to be more prone to crank sensor B issues.

FAQ

Can I clear P0389 and keep driving if the car seems fine?

You can clear the code, but if the underlying problem is still there, P0389 will usually come back. The car might seem fine until the sensor fails again, possibly leaving you with a no-start. It’s better to diagnose and fix the cause instead of just erasing the code.

Is P0389 the same as a bad crankshaft position sensor every time?

No. A bad sensor is common, but wiring faults, connector corrosion, or a damaged tone ring can cause the same code. Testing power, ground, and signal before replacing parts helps avoid misdiagnosis.

How urgent is it to fix a P0389 code?

It’s fairly urgent. While the car may still run, an intermittent crank signal can cause sudden stalling or a no-start condition. For safety and reliability, you should address P0389 as soon as possible.

Can a weak battery or charging system cause P0389?

A weak battery or failing alternator can create low voltage conditions that affect sensor operation, but they’re not the most common cause. However, if you have starting issues and multiple electrical codes, it’s smart to test the battery and charging system during diagnosis.

Do I need a crankshaft relearn after replacing the sensor for P0389?

On many modern vehicles, yes. After replacing the crank sensor, the ECU may require a crankshaft position relearn procedure using a capable scan tool. This helps the ECU adapt to the new sensor’s signal and prevents recurring codes or drivability issues.