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U0252 Lost Communication With Lighting Control Module - Rear B

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Module B for rear lighting is the second unit driving lamps at the back end, and in practice it is often the trailer electronics. GM's code list for the 2011 Saab 9-5 assigns U0252 to the trailer interface control module. Ford does the same: on 2021-2023 F-150, 2022-2024 F-150 Lightning, Expedition, Navigator and the 2024 Ranger, the body control module, cluster or steering module records U0252, often with U0137, when the trailer module (TRM) drops off CAN; a five-minute power-down and new TRM software cured it (SSM 53236). Super Duty trucks of 2023-2025 showed the same pair when ground point G201 was not torqued correctly (SSM 53980), and a BCM self-test may leave a harmless U0252:87 history entry (SSM 51578). Trailer lamps or trailer brake messages fail; no MIL.

Likely causes

Trailer or rear lighting module stuck off the bus, software needs reset or update (Ford TRM)
Loose or badly tightened body ground shared with the module (Ford G201)
Damaged or corroded harness and connectors at the rear or tow bar area
Stored history entry from a module self-test without a real fault

Symptoms

  • Trailer brake module fault or trailer warning in the cluster
  • Trailer lamps or rear lighting functions inoperative
  • Further U codes such as U0137 in body control module, cluster or steering module

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–600
Time0.3–2 h

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

Parts involved

rear lighting module bvehicle bus wiring

Related codes

U0553U0137U0182U0140

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, saabwisonline.com.