P0391 Fault Code

Camshaft Position Sensor B Circuit Range/Performance (Bank 2)

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0391 fault code indicates an issue with the Camshaft Position Sensor B Circuit on Bank 2. This code is part of the system responsible for monitoring the camshaft position, which is crucial for proper engine timing and operation. When the performance or range of this sensor falls outside of acceptable limits, the engine control module (ECM) triggers this code.

• The camshaft position sensor detects the position of the camshaft relative to the crankshaft.
• A malfunction in this sensor can result in improper engine timing, leading to poor performance.
• It’s important to address this code promptly to prevent further engine issues.

What are the symptoms of the P0391 code?

Symptoms associated with the P0391 code may include:

• Rough idling or misfiring of the engine.
• Difficulty starting the engine or no start condition.
• Hesitation during acceleration.
• Illuminated check engine light.
• Decreased fuel efficiency due to improper timing.

What causes the P0391 code?

Several factors can trigger the P0391 code, including:

• A faulty camshaft position sensor.
• Wiring issues, such as damaged, corroded, or frayed wires that affect the signal transmission.
• Poor electrical connections at the sensor or ECM.
• Timing belt issues that incorrect camshaft alignment.
• Engine control module (ECM) faults affecting sensor functionality.

How to fix P0391?

To resolve the P0391 code, follow these steps:

• Perform a visual inspection of the camshaft position sensor and its wiring for damage or disconnection.
• Test the camshaft position sensor with a multimeter to ensure it meets specifications.
• Replace the camshaft position sensor if it's found to be faulty.
• Repair any wiring issues or bad connections.
• After repairs, reset the trouble codes and test drive the vehicle to ensure proper operation.