What does it mean?
B1237 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Short in the Passenger's Air Mix Control Motor Circuit .
Symptoms
- Passenger side air temperature is stuck at one extreme
- Repeated clicking or knocking behind the glove box, especially in the first minutes after start-up
- The actual blend position in live data does not follow the commanded value
- The driver side may still be controllable on dual zone systems
- The code comes back very soon after it is cleared
Likely causes
- Actuator control wire chafed against a bracket behind the glove box and shorted to ground
- Internally shorted actuator motor after it stalled against a jammed blend door
- Blend door or its linkage broken, causing the motor to draw excessive current
- Water from a blocked evaporator drain reaching the actuator connector
- Harness pinched between the HVAC case and the glove box frame
- Control wire shorted to a 12 V feed sharing the same loom
How to fix it
- Listen behind the glove box while sweeping the passenger temperature setting to find a stalled actuator
- Unplug the actuator; if the code changes to an open fault, the actuator itself is shorted
- Measure the motor windings, where a near-zero value confirms an internal short
- Remove the actuator and check that the blend door and its linkage move freely by hand
- Inspect the harness for chafe and pinch points and check the connector for water from the evaporator drain
- Replace the actuator and clear any obstruction in the door, then calibrate the climate module and verify operation