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U0136 Lost Communication With Differential Control Module - Rear

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0136 is set when a listener misses the rear differential control module, which operates an electronic limited-slip or twin-clutch rear drive unit. GM's 2019 tables document it in the ECM of the Cadillac XT4 (LSY engine): if message $1CF from the rear drive module stays absent for 10 s while bus A is active and supply exceeds 11 V, the ECM stores U0136 as a Type B fault, so the MIL comes on after two trips. Saab's 2011 9-5 list (XWD all-wheel drive) also names the rear differential module and adds byte 71 for invalid data. Implausible rear-differential data has its own code U0437; the front axle uses U0135. Rear torque distribution switches off with a warning, and the car usually continues with front-wheel drive.

Likely causes

Fuse, supply, ground or CAN wiring of the rear drive module faulty
Corroded or damaged connector at the rear axle, exposed to spray water
Rear differential control module internally faulty

Symptoms

  • AWD or rear differential warning
  • Car drives with front-wheel drive only, less traction
  • MIL after two trips on GM vehicles

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–2,000
Time0.5–4 h

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

Parts involved

rear differential modulecan bus wiring

Related codes

U0437U0135U0114

References: gsi.ext.gm.com, saabwisonline.com, law.cornell.edu.