P0389
UniversalCrankshaft Position Sensor B Circuit Intermittent
The crankshaft position sensor provides information used by the engine computer to determine crankshaft position and speed. This code indicates that the signal or electrical circuit for sensor B is intermittent. Depending on the vehicle and how the signal is used, the engine may run poorly, stall, or have trouble starting. The code identifies a detected circuit condition; it does not by itself prove the sensor needs replacement.
⚠️ Before You Begin (Safety First)
If the engine stalls, loses power, or becomes difficult to control, pull over safely and arrange for diagnosis rather than continuing to drive. Intermittent engine problems can return without warning. Keep clear of moving and hot engine parts during checks.
Common Symptoms
- There may be no noticeable symptoms if the signal interruption is brief or does not affect engine operation.
- The engine may crank longer than usual or intermittently fail to start if the computer cannot reliably use the crankshaft signal.
- The engine may stumble, run roughly, or lose power if the signal becomes unreliable while running.
- The engine may stall if the interruption prevents the computer from reliably determining crankshaft position or speed.
- The check-engine light may be on; other warning lights or codes may appear depending on the vehicle.
Common Causes
- An intermittent fault within crankshaft position sensor B.
- A loose, damaged, corroded, or contaminated sensor connector or connection.
- Wiring that is damaged, chafed, poorly routed, or intermittently open or shorted.
- An intermittent issue with circuit power, ground, or a related connection, where applicable to the vehicle's design.
- A signal disturbance or related engine-control issue that requires further testing to identify.
Diagnostic Steps
- Record this code and any other stored codes before clearing anything; related codes and their timing can help guide diagnosis.
- Note when the problem occurs, such as during starting, while driving, or when the engine is hot, and whether the engine stalls or runs unevenly.
- With the engine off and cool, visually inspect accessible sensor wiring and connectors for looseness, damage, corrosion, or contact with hot or moving parts. Do not pull on wires or probe connector terminals.
- If a connector appears loose or dirty, consult vehicle-specific service information before disconnecting or cleaning it; avoid forcing or bending terminals.
- If the code returns or the engine stalls, arrange professional diagnosis rather than replacing parts based on the code alone.
When to Call a Professional
A technician can review stored codes and freeze-frame data, monitor the crankshaft signal during the reported condition, and inspect the sensor circuit and connectors. Wiring diagrams and vehicle-specific service information help distinguish a sensor fault from a connector, wiring, power, ground, or related signal problem. Signal testing may require suitable scan or electrical test equipment.
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Commonly Asked Questions
Does P0389 prove that crankshaft position sensor B has failed?
No. It indicates an intermittent condition in sensor B's circuit. The sensor, connector, wiring, or another related electrical issue may be involved, so testing is needed before choosing a repair.
Can I keep driving with P0389?
It depends on the symptoms. If the engine runs normally, arrange diagnosis promptly and watch for changes. If it stalls, loses power, or becomes unreliable, stop driving when safe and seek assistance.
Why might the code appear only sometimes?
A loose connection, damaged wire, or failing component can interrupt the signal only under certain conditions, such as vibration or changes in temperature. The specific cause needs to be confirmed on the vehicle.
What helps distinguish a sensor problem from a wiring problem?
A technician can inspect the circuit and connector, review scan data, and test the signal and related electrical connections using vehicle-specific information. The code alone does not distinguish these causes.
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.