Code Definition

B1278 — Servo Motor Potentiometer Foot Circuit Short To Battery

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1278

B1278 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1278 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1278 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Body Control Module (BCM) or HVAC control module sets this code when it detects a short to battery voltage on the foot mode door servo motor's internal position potentiometer signal. The potentiometer normally returns a variable voltage between approximately 0.5V and 4.5V referenced to a 5V supply, reporting the actual position of the foot mode door that routes cabin airflow toward the floor outlets. When the signal wire becomes shorted to a battery feed or ignition feed, the controller sees a voltage well above the 5V reference and recognises the reading as electrically impossible. Driver...

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