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 understanding where a part of the 4-wheel drive system is located. It's like if you were playing a video game and the controller couldn't tell where the joystick was pointing.
The C0091 code indicates a problem with the position sensor in the power transfer unit of a 4WD/AWD system. This sensor helps the car's computer know the position of the transfer unit to ensure proper operation.
The power transfer unit is responsible for distributing power between the front and rear wheels in a 4WD/AWD vehicle. The position sensor provides feedback to the vehicle's control module about the current position of the transfer unit. If the sensor fails or provides incorrect data, the control module may not be able to correctly manage the power distribution, leading to potential drivability issues.
• 4WD/AWD warning light on the dashboard
• Inability to engage or disengage 4WD/AWD
• Unusual noises from the drivetrain
• Faulty position sensor
• Damaged wiring or connectors
• Malfunctioning control module
4WD: Four-Wheel Drive
AWD: All-Wheel Drive
OBD-II: On-Board Diagnostics, Second Generation
• Check for any other related diagnostic trouble codes.
• Inspect the wiring and connectors to the position sensor.
• Test the position sensor for proper operation.
• Replace the faulty position sensor.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the control module if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Ford Explorer
• Jeep Grand Cherokee
• Toyota 4Runner
• Regularly inspect and maintain the drivetrain components.
• Ensure connectors and wiring are secure and free from corrosion.
• Follow the manufacturer's maintenance schedule.
Sensor Issue
• Have the vehicle inspected by a professional if the 4WD/AWD light comes on.
• Avoid using 4WD/AWD until the issue is resolved to prevent further damage.
Check with the vehicle manufacturer for specific warranty coverage related to drivetrain components.
This code has been historically associated with sensor failures in vehicles with complex 4WD/AWD systems.
Moderate – It is advisable to address this issue soon to prevent potential drivability problems.
Driving with a malfunctioning 4WD/AWD system can affect vehicle handling and safety. Address the issue promptly.
• Vehicle in a safe, stationary position.
• Access to the vehicle's OBD-II port.
The position sensor is typically located on or near the power transfer unit, which is part of the drivetrain system beneath the vehicle.
Q: Can I drive my car with this code?
A: It's best to avoid using the 4WD/AWD system until the issue is fixed to prevent further damage.
Q: How can I reset the 4WD/AWD light?
A: The light can be reset by fixing the underlying issue and clearing the code with an OBD-II scanner.
Pro · Four-system diagnostics
A handheld scanner aimed at engine, transmission, ABS, and airbag diagnostic work.
Chassis and ABS faults usually need a scanner that can read brake-system data directly.
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Universal · Torque wrench
Useful when reassembly torque matters for wheel, suspension, and under-hood fasteners.
Useful when wheel, hub, or suspension hardware needs correct reassembly torque.
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Universal · Drive-on ramps
Helpful for safer access underneath the vehicle during exhaust, EVAP, and underbody inspection work.
Helpful for safer access during underbody inspection work.
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