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U011B Lost Communication With Rocker Arm Control Module A

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

U011B covers the first rocker arm control module. On overhead-cam engines that shut cylinders down or change valve lift, a solenoid routes engine oil to unhook a pin coupling two rocker arms; the cam-driven arm then moves on its own and the valve stays shut. Where a maker hands this switching to a dedicated controller, the engine controller sets U011B when that unit's messages stop. No manufacturer documents the code publicly. CARB requires lost digital communication to be coded separately and also obliges makers to supervise systems that vary valve timing or lift. U011C is the second module, U041C stands for invalid data from this one. Expect the MIL, switching of valve lift or cylinder deactivation locked out and higher fuel use.

Likely causes

Rocker arm module without power or ground
Oil-soaked or heat-damaged connector on the cylinder head
Damaged CAN wiring between module and engine controller
Rocker arm control module internally faulty

Symptoms

  • MIL on
  • Cylinder deactivation or valve lift switching inactive
  • Higher fuel consumption

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time1–4 h

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

Parts involved

rocker arm module acan bus wiring

Related codes

U011CU041CU0100

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