Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer is having trouble understanding the timing of one of the engine's camshafts on one side of the engine.
This code indicates that the engine control module (ECM) has detected a timing error with the camshaft position sensor 'B' on bank 2 of the engine.
The camshaft position sensor monitors the position and speed of the camshaft, which is critical for engine timing. Bank 2 refers to the side of the engine opposite to bank 1. A segment timing error suggests that the sensor is not reading correctly, possibly due to a misalignment or a faulty sensor.
• Check Engine Light is on
• Engine misfires
• Poor fuel economy
• Rough idling
• Difficulty starting the engine
• Faulty camshaft position sensor
• Wiring issues such as short or open circuits
• Timing chain or belt issues
• Misaligned camshaft
• Faulty ECM
Camshaft: A shaft in the engine that controls the opening and closing of the intake and exhaust valves.
ECM: Engine Control Module, the computer that controls engine functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage.
• Check the camshaft position sensor for proper operation.
• Verify the timing chain or belt alignment.
• Test the ECM for faults.
• Replace the camshaft position sensor.
• Repair or replace damaged wiring or connectors.
• Adjust or replace the timing chain or belt.
• Realign the camshaft if necessary.
• Replace the ECM if it is faulty.
• OBD-II scanner
• Multimeter
• Socket set
• Timing light
• Screwdriver set
$150 - $600
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regularly inspect and maintain engine components.
• Replace timing belts or chains as recommended.
• Ensure wiring and connectors are in good condition.
Sensor Issue
• Do not ignore the Check Engine Light; get it diagnosed promptly.
• Regular maintenance can prevent such issues.
• Consult a professional mechanic if unsure.
Check with the vehicle manufacturer for specific warranty coverage related to engine components.
This code has been more common in vehicles with higher mileage or those that have not had regular maintenance on timing components.
Moderate – While the vehicle may still run, ignoring this issue can lead to more severe engine problems.
Driving with a faulty camshaft position sensor can lead to increased emissions and potential engine damage.
• Engine at operating temperature
• Vehicle in park or neutral
The camshaft position sensor is typically located near the camshaft, often on the cylinder head or engine block.
Q: Can I drive with a P139B code?
A: It's not recommended to drive for extended periods with this code, as it can lead to engine damage.
Q: How do I know if my camshaft position sensor is bad?
A: Symptoms include engine misfires, poor fuel economy, and difficulty starting the engine.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
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.