What does it mean?
B1891 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Power Liftgate Control Circuit 2 Low .
Symptoms
- Power liftgate will not move in one direction, or will not operate at all
- Module beeps and flashes as it aborts the cycle, and the gate must be worked by hand
- A fuse feeding the drive circuit may blow repeatedly
- Movement is possible only after a battery reset and then fails again
- Motor buzzes or hums without proper travel
Likely causes
- Motor control wire shorted to ground where the harness flexes at the liftgate hinge conduit
- Water in the spindle drive or module connector bridging the output to ground
- Seized or binding spindle drive motor overloading the output driver
- Chafed loom inside the tailgate where it passes a sharp metal edge or grommet
- Corroded ground point or connector on the gate causing an abnormal reference
- Liftgate control module output stage failed shorted
- Damage after aftermarket camera, spoiler or trim installation in the gate
How to fix it
- Confirm battery condition and check the relevant fuse before any circuit testing
- Read the module codes and identify which drive output is reported low
- Disconnect the spindle drive and measure the control wire to ground with the module unplugged; a low reading proves a shorted wire
- If the wiring measures clean, check the motor itself for a shorted winding or a mechanically seized drive
- Open the hinge conduit and inspect the loom carefully, flexing it while measuring to catch an intermittent short
- Repair the damaged wiring with correct terminals and protect it inside the conduit
- Replace the liftgate control module last, only after wiring and motor are proven good