Network, generic

U0074 Control Module Communication Bus B Off

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U0074 tells that a module dropped into bus off on Bus B, which the makers that use it assign to an extra powertrain network. GM's 2019 ECM tables call it the Powertrain Expansion CAN, and the LT5 injection module rates its Bus B check Type B, two trips. On 2014-18 trucks and SUVs, PIP5427 ties U0074 to a lost link between ECM and fuel pump module that drives fuel pressure far above target and sets P2635; the communication fault is to be fixed first. FCA's label for the code refers to its Dedicated Powertrain CAN (D-PT): a PCM reflash cures it on the 2019 Ram 1500 eTorque, and on 2022-24 Wranglers it comes with a binding shifter. Ford lists it on 2017-18 F-150s with a badly secured transmission harness, and its diesel PCMs set it when a line stays shorted or open longer than 10 ms.

Likely causes

Damaged or poorly routed powertrain harness on Bus B
Engine module software fault, fixed by reprogramming
Loose connector, bent pin or badly seated fuse on a Bus B module

Symptoms

  • Service Engine Soon lamp or MIL on
  • Fuel pressure well above the requested value (GM trucks)
  • Shifter binds or shift concerns
  • No crank or start-stop inoperative

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–900
Time0.5–5 h

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

Parts involved

can bus wiringcan terminating resistorcontrol module

Related codes

U0037U0073U0075U0101P2635

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.