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DTC codes / B01xx · Airbags, seats, doors, lights and comfort systems / B0125

B0125Driver Side Mirror Position Sensor

B0125 indicates that the body control module (BCM) or driver door module has detected a fault in the driver side mirror position sensor circuit, meaning the voltage or signal from the sensor does not match the expected range for the mirror's commanded position. The computer uses this sensor to know where the mirror glass is aimed so it can store and recall memory positions and properly control the mirror motors.

SystemBody
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

  • The driver side mirror may not move to the correct position when a memory preset is selected.
  • The mirror may move in only one direction or not at all when adjusted with the switch.
  • The mirror glass may appear to be in the wrong position after the vehicle is restarted.
  • A warning light or message may appear on the dashboard indicating a mirror system fault.
  • Often no symptoms besides the warning light, especially if the mirror still adjusts manually.
  • The mirror may move erratically or stop partway through its travel.

Common causes, most likely first

  1. A failed driver side mirror position sensor inside the mirror assembly.
  2. Damaged or chafed wiring in the door jamb boot or between the mirror and the door module.
  3. Corroded or loose electrical connectors at the mirror or door module.
  4. A faulty driver door module or body control module that cannot read the sensor signal.
  5. A binding or damaged mirror motor mechanism that prevents the sensor from reaching its expected range.
  6. Water intrusion into the mirror housing causing sensor or connector corrosion.

How to diagnose and fix it

  1. Use a scan tool to read the B0125 code and check for any related body codes in the door module or BCM.
  2. Visually inspect the mirror housing, door jamb wiring boot, and connectors for damage, corrosion, or water intrusion.
  3. Disconnect the mirror connector and check for the correct reference voltage and ground at the sensor circuit.
  4. Test the position sensor signal with a multimeter while moving the mirror through its range to see if the voltage changes smoothly.
  5. If the sensor signal is missing or erratic, replace the driver side mirror assembly or the sensor if it is serviced separately.
  6. If the sensor tests good, check continuity and resistance of the wiring between the mirror and the door module.
  7. Clear the code and verify the mirror operates correctly through its full range and that the code does not return.

Mirror position sensor faults often misdiagnosed

  • A binding mirror mechanism can cause the position sensor to report an out-of-range value even when the sensor itself is good, so always check for mechanical binding before replacing parts.
  • The driver side mirror position sensor is often part of the mirror assembly and may not be available separately, leading to unnecessary replacement of the entire mirror when the real fault is a chafed wire in the door jamb.
  • Water intrusion into the mirror housing is a common cause on vehicles that are frequently parked outside or driven in wet conditions, and the corrosion can mimic a failed sensor.
  • A weak or failing driver door module can set B0125 even though the mirror and sensor are functioning correctly, so module power and ground should be verified.
  • The code can be set intermittently by a loose connector that only loses contact when the door is slammed or the mirror is adjusted, making it important to wiggle-test wiring while watching live sensor data.

Can I keep driving with B0125?

The vehicle remains safe to drive because the driver side mirror position sensor only affects mirror memory and automatic adjustment features, but you should manually verify the mirror is aimed correctly before driving and avoid relying on memory presets until the fault is repaired.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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