Network, generic

U0251 Lost Communication With Running Board Control Module B

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Letter B denotes a second running board controller, which only exists where each side has its own unit. Ford's documented power running boards rely on a single running board control module (RBM): its 2015–2022 bulletins describe one RBM that logs U3003:16 and turns the feature from Auto to Off after a low or flat battery (SSM 50154) and one whose software flips the setting on F-Super Duty (SSM 52411). No manufacturer publishes a vehicle that uses U0251. Under the J2012 scheme, a body controller or gateway would set it once frames from unit B stop. Because such units live under the body near the board motors, water, road salt and stone damage at plugs and wiring are the main suspects. The driver finds the board on one side stuck in or out. Unit A is U0244; invalid data from B are U0552.

Likely causes

Water or salt corrosion at underbody connectors and wiring
Low or flat battery that left the module offline
Module without power or ground (fuse)
Module internally faulty

Symptoms

  • Running board on one side does not deploy or retract
  • Running board fault message in the cluster

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–900
Time0.3–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

running board module bvehicle bus wiring

Related codes

U0244U0552U0545

References: static.nhtsa.gov, static.nhtsa.gov, en.wikipedia.org.