Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble reading signals from a sensor that helps it know the position of a part in the engine. It's like trying to read a clock with a broken hand.
The P0391 code indicates that the signal from the camshaft position sensor B on bank 2 is out of the expected range or not performing as it should.
The camshaft position sensor monitors the position of the camshaft and sends this information to the engine control module (ECM). The ECM uses this data to control the timing of the ignition and fuel injection. If the signal from sensor B on bank 2 is erratic or outside expected parameters, the P0391 code is triggered.
• Check Engine Light illuminated
• Engine misfires
• Poor engine performance
• Faulty camshaft position sensor B
• Wiring issues such as shorts or open circuits
• Timing chain or belt problems
Camshaft: A shaft in the engine that controls the opening and closing of the valves.
ECM: Engine Control Module, the computer that manages the engine's functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage.
• Test the camshaft position sensor B for proper operation.
• Replace the camshaft position sensor B if faulty.
• Repair or replace damaged wiring or connectors.
• Inspect and replace timing chain or belt if necessary.
• OBD-II scanner
• Multimeter
• Socket set
$100 - $300
Moderate
• Toyota Camry
• Honda Accord
• Ford F-150
• Regular maintenance and inspection of engine components.
• Timely replacement of timing belts or chains.
• Ensure wiring and connectors are in good condition.
Sensor Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional if unsure.
• Regularly maintain the vehicle to prevent sensor issues.
Check with the vehicle manufacturer for warranty coverage on engine sensors.
The P0391 code has been associated with sensor issues in various vehicle models over the years, often linked to wiring problems or sensor failures.
Moderate – It is advisable to address this issue soon to prevent potential engine performance problems.
Driving with a malfunctioning engine sensor can lead to reduced performance and increased emissions.
• Engine at operating temperature
• Vehicle in a safe, stationary position
The camshaft position sensor B on bank 2 is typically located near the engine's camshaft on the opposite side of bank 1.
Q: Can I drive with a P0391 code?
A: While the vehicle may still be drivable, it's best to address the issue to avoid potential engine damage.
Q: How do I reset the Check Engine Light after fixing the issue?
A: Use an OBD-II scanner to clear the code after repairs are completed.
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Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.