What does it mean?
B1929 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Left Rear Window Control Circuit Open .
Symptoms
- Left rear window is completely dead, with no sound from the motor
- Neither the rear switch nor the driver master switch has any effect
- Other functions in the same door may also be dead if the shared harness is broken
- Fault may be intermittent at first, working only when the door is in a certain position
- Window may be stuck open, which is a security concern
Likely causes
- Broken conductor in the door jamb boot harness, which flexes every time the rear door is opened
- Motor or switch connector unplugged or not latched after door trim, speaker or child lock work
- Open motor winding inside the window motor
- Blown fuse or an interrupted feed to the rear window circuit
- Corroded or backed out terminal in the door or module connector
- Wire cut during aftermarket accessory installation in the rear door
- Module output driver failed open
How to fix it
- Check the fuse and confirm supply voltage at the door module before further diagnosis
- Read the codes and watch the module output while commanding the window to move
- Confirm the motor and switch connectors are seated and locked, because they are often left off after trim work
- Measure continuity from the module connector to the motor connector on both control wires
- Peel back the jamb boot and flex the harness while measuring, as broken strands inside good looking insulation are typical here
- Check other circuits in the same door, since several dead functions point to a common broken harness
- Replace the motor if its winding is open, and the module only as the final step, then reinitialise the window function