What does it mean?
B2451 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Sliding Door Unlatch or Cinch Motor (PTG) / Unlatch Motor (PSD) Short Low .
Symptoms
- The auxiliary heater will not run and locks out after a failed start attempt
- No ticking sound from the metering pump when a heater start is commanded
- The heater circuit fuse blows repeatedly
- Cabin preheating or remote start heating does not work
- An auxiliary heating warning appears in the driver display
Likely causes
- Chafed dosing pump wiring rubbing against the underbody or a chassis bracket
- Water and road salt corrosion in the fuel pump connector, common on underfloor mounted pumps
- Shorted winding inside the metering pump
- Loom crushed by a heat shield, an exhaust clamp or an underbody panel
- Damage from road debris striking the exposed section of harness
- Short between the pump drive wire and an adjacent ground in a shared connector
- Failed output driver inside the auxiliary heater control unit
How to fix it
- Check the heater fuse first, since a grounded output usually takes the fuse with it
- Command a heater start and listen underneath for the metering pump ticking
- Unplug the pump and measure resistance from each drive wire to ground with the control unit also disconnected
- Measure the pump winding resistance and compare it with the specification to separate a shorted pump from a shorted harness
- Follow the loom along the underbody looking for chafe points, crushed sections and corrosion at every connector
- Repair the harness with sealed joints and secure it clear of the exhaust and any moving parts
- Replace the metering pump if it is internally shorted, then reset the heater lockout and run a test cycle