Crankshaft Position Sensor B Circuit Intermittent
The P0389 code indicates an intermittent signal from the crankshaft position sensor B circuit. This sensor monitors engine speed and position for fuel injection and ignition timing. An intermittent fault can cause erratic engine behavior, stalling, or no-start conditions. Common causes include a faulty sensor, damaged wiring, poor electrical connections, or issues with the reluctor ring.
1. Most Common Causes
- Faulty or worn crankshaft position sensor B
- Loose, oxidized, or corroded electrical connections at the sensor connector
- Damaged, chafed, or vibration-prone wiring causing intermittent breaks
- Poor ground in the sensor circuit
- Mechanical damage to the reluctor ring or crankshaft teeth affecting signal
- Electromagnetic interference from other electrical components
2. Symptoms You Will Notice
- Engine stalling or hesitation
- Hard starting or no-start condition
- Check Engine Light illuminated
- Rough idle or misfires
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect sensor and wiring for damage or corrosion.
Step 3: Test sensor resistance and signal output with a multimeter or oscilloscope.
Step 4: Check reluctor ring for damage or debris.
Step 5: Repair or replace faulty components as needed.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The intermittent signal can cause sudden stalling or loss of engine power, leading to a potential accident. Have the vehicle diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the cause. A sensor replacement is usually $30-$80, plus diagnostic time.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.