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U041C Invalid Data Received From Rocker Arm Control Module A

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

U041C relates to rocker arm control module A, the controller that switches oil-actuated rocker arms to change valve lift or shut cylinders down. The engine controller stores it when the module's lock-state or feedback frames arrive with implausible content, wrong counters or invalid values. No manufacturer documents U041C publicly, and it is open which engines use a separate module. CARB treats systems that vary valve lift or timing as monitored emission controls and asks for rationality checks of digital inputs, separate from lack-of-communication codes. Without trusted feedback the controller will usually keep all cylinders at normal lift and record the fault with the MIL; fuel use rises and running may be uneven. U011B is lost contact; module B has U041D.

Likely causes

Low oil pressure or sticking switching solenoid causing implausible lock-state feedback
Rocker arm control module A internally faulty
Connector or bus wiring fault at module A

Symptoms

  • Check engine light
  • Cylinder deactivation or valve lift switching locked out
  • Higher fuel consumption

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,200
Time0.5–4 h

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

Parts involved

rocker arm module acan bus wiring

Related codes

U011BU041DU011C

References: law.cornell.edu, en.wikipedia.org.