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DTC codes / B01xx · Airbags, seats, doors, lights and comfort systems / B0126

B0126Passenger Side Mirror Position Sensor

B0126 indicates that the passenger side mirror position sensor circuit has a fault, meaning the body control module (BCM) or mirror control module cannot reliably read the mirror's horizontal or vertical position. The computer detects an out-of-range voltage, an open circuit, or a short to ground or power on the sensor signal wire, which prevents the memory and reverse-tilt features from working correctly.

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

Symptoms you may notice

  • The passenger side mirror may not move when using the adjustment switch or may move in only one direction.
  • The mirror memory function may fail to return the mirror to its saved position after being moved.
  • The reverse tilt-down feature may not work or may move the mirror to an incorrect angle.
  • The mirror may appear to have a mind of its own, drifting or stopping at the wrong position.
  • Often no symptoms besides the warning light, especially if the mirror still adjusts manually.

Common causes, most likely first

  1. A faulty passenger side mirror position sensor inside the mirror assembly.
  2. Damaged or chafed wiring in the door jamb boot or at the mirror connector.
  3. Corroded or loose electrical connectors at the mirror or the door control module.
  4. A failed passenger side mirror motor assembly that incorporates the position sensor.
  5. A malfunctioning door control module or body control module (BCM) that cannot process the sensor signal.
  6. A blown fuse or poor ground connection affecting the mirror circuit.

How to diagnose and fix it

  1. Check for any related technical service bulletins (TSBs) or recalls for the passenger side mirror on your vehicle make and model.
  2. Inspect the mirror connector and the door jamb wiring harness for corrosion, chafing, or loose pins, and repair as needed.
  3. Measure the sensor reference voltage and ground at the mirror connector with a digital multimeter (DMM) to confirm power and ground are present.
  4. Back-probe the sensor signal wire and observe the voltage while moving the mirror through its full range to see if the signal changes smoothly.
  5. If the signal is erratic or missing, remove the mirror glass and test the position sensor directly with a DMM, comparing to factory specifications.
  6. Replace the passenger side mirror assembly or the faulty sensor/motor component if testing confirms it is defective.
  7. Clear the code and perform a mirror calibration or relearn procedure if required by the vehicle manufacturer, then verify the fix.

What the mirror sensor code really means

  • A weak or dying car battery can cause false B0126 codes because the mirror module may not initialize properly on low voltage.
  • The position sensor is often a potentiometer that wears out over time, causing dead spots that only show up at certain mirror angles.
  • Water intrusion into the mirror housing is a common cause of sensor failure, especially after car washes or heavy rain.
  • The code may set intermittently and not turn on the warning light until the fault occurs several times, so a stored code without symptoms can still be real.
  • Replacing the mirror assembly without checking the door jamb wiring first is a common misdiagnosis that leads to repeat failures.

Can I keep driving with B0126?

The vehicle remains safe to drive because the passenger side mirror still provides a view, but you should avoid relying on memory or reverse-tilt features until repaired. Manually adjust the mirror as needed and have the fault diagnosed when convenient.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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