Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with the sensor that tells the car's computer where the back wheels' special gear is. It's like if your toy car's wheels couldn't turn because something was stuck.
The code indicates an issue with the position sensor in the rear differential actuator, which is responsible for detecting the position of the actuator in the 4WD/AWD system.
The C0099 code is triggered when the vehicle's control module detects a malfunction in the rear differential unit actuator position sensor. This sensor is crucial for ensuring the proper engagement and disengagement of the rear differential in vehicles equipped with 4WD or AWD systems. A fault in this sensor can lead to improper functioning of the drivetrain.
• 4WD/AWD system malfunction light
• Inability to engage or disengage 4WD/AWD
• Unusual noises from the rear differential
• Faulty position sensor
• Wiring issues or poor connections
• Defective actuator
4WD: Four-Wheel Drive
AWD: All-Wheel Drive
Actuator: A device that causes a mechanical system to operate
• Check for any stored codes and clear them to see if they return.
• Inspect the wiring and connections to the position sensor.
• Test the actuator and sensor for proper operation.
• Replace the faulty position sensor.
• Repair or replace damaged wiring or connectors.
• Replace the actuator if found defective.
• OBD-II scanner
• Multimeter
• Wrench set
$200 - $600
Moderate
• Toyota RAV4
• Subaru Outback
• Ford Explorer
• Regularly inspect and maintain the differential system.
• Ensure proper lubrication of differential components.
• Check for any unusual noises and address them promptly.
Sensor Issue
• Avoid driving in extreme conditions until repaired.
• Seek professional diagnosis if unsure.
• Regular maintenance can prevent similar issues.
Check with your vehicle manufacturer for warranty coverage on drivetrain components.
This code has been reported in vehicles with higher mileage or those frequently used in off-road conditions.
Moderate – Should be addressed soon to avoid potential drivetrain damage.
Ignoring drivetrain issues can lead to unsafe driving conditions and potential legal liabilities.
• Vehicle in park or neutral
• Engine running
The position sensor is located on the rear differential, typically near the actuator mechanism.
Q: Can I drive with a C0099 code?
A: It's not recommended to drive with this code active, as it may affect the vehicle's 4WD/AWD capabilities.
Q: How do I reset the C0099 code?
A: Use an OBD-II scanner to clear the code, but ensure the underlying issue is fixed first.
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.
View on Amazon
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.
View on Amazon
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.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.