What does it mean?
OBD II fault code B2326 is a manufacturer specific code that is defined by Ford, Lincoln, Mazda, Mercury, and Nissan as “Mirror Driver Vertical Feedback Potentiometer Circuit Short to Battery” and on these applications, code B2326 is set when the PCM (Powertrain Control Module) or, Body Control Module, detects a short circuit in an electronically controlled side view mirrors’ feedback loop.
NOTE: In this definition, “Vertical feedback” refers to the circuit that controls the movement of the mirror around the vertical (side-to-side) axis, and “Potentiometer” refers to the device in the mirror that provides the controller with information on the mirrors’ position relative to a base setting.
In practical terms, the adjustment and control of side view mirrors is accomplished by small electric motors that can tilt a mirror either from side to side (vertical axis), or up and down, (horizontal axis), or both at the same time, depending on the application. On many, if not most, applications, the amount of movement is programmable, meaning that one or both mirrors can be programmed to move only within a range set by the programmer.
To enable programming, each drive motor is connected to a potentiometer, which is a type of variable resistor that passes a variable voltage, depending where in its rotation the moving part of the potentiometer (aka, the wiper) stops on a resistive winding or strip. Refer to the image below. If the wiper is stopped halfway along the resistive strip, the potentiometer will theoretically pass only 50% of the voltage that entered it.
Therefore, by moving the wiper to different positions on the resistive strip, the exiting voltage can be adjusted to serve as a sort of baseline reference voltage a controller can use to move a mirror between an upper and lower voltage limit. Thus, when a mirror is being programmed, the controller will remember both the upper and lower limits of the voltage generated by the potentiometer during the programming procedure.
However, during the mirror’s movement, the current that is allowed to pass through the potentiometer also serves as a form of feedback, and the controller will cut power to the actuator when either the previously programmed upper or lower voltage limit is reached. In practice, when this feedback voltage is interrupted or absent, the controller cannot control the mirror and code B2326 will be set, which depending on the application, may, or may not trigger a warning light.
The image below shows detail of the mechanics of an electronically adjustable/controlled side view mirror. Note the two drive motors and the potentiometer that is geared to each. Note that each motor controls adjustment of the mirror around one axis. Be aware that while the example shown here is somewhat typical, the actual arrangement and appearance of the various components in an adjustable mirror can differ greatly between applications.
Symptoms
- The driver mirror drives to one end of its side to side travel and will not return.
- Memory recall positions the mirror wrongly or does not move it at all.
- The mirror may move on its own when the doors are unlocked or another door function is used.
- Reverse tilt and memory storing no longer work for that mirror.
- The feedback value in live data sits at full scale whatever the mirror does.
Likely causes
- Feedback wire chafed inside the door against a permanently live conductor such as the window motor feed.
- Water in the mirror housing or the door connector bridging the signal contact to a power contact.
- Bent, spread or pushed back terminal in the mirror or controller connector touching a supply pin.
- Internal short between the potentiometer wiper track and the drive motor feed inside the actuator.
- Harness pinched or trapped when the door trim, mirror or window regulator was refitted.
- Aftermarket wiring for speakers, lamps or alarm sensors spliced into the door loom near the mirror circuits.
- Controller input stage failure.
How to fix it
- Read the codes and check the vertical feedback value; a reading pinned at maximum indicates the line is held at supply voltage.
- Unplug the mirror connector and measure the feedback wire from the harness side with the ignition on.
- Battery voltage still present with the mirror disconnected places the short in the wiring; voltage that disappears places it inside the actuator.
- Inspect the door harness along the inner panel, the regulator rail and the rubber boot for chafing, crushing and added wiring.
- Check the mirror housing and connector for water, corrosion and failed seals, and dry everything before retesting.
- Repair the damaged wiring with sealed crimped joints and reroute the loom away from moving parts.
- Replace the mirror actuator when the short is proven internal, then reprogram the mirror memory positions.