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U02AD Lost Communication With Turbocharger/Supercharger Boost Control B

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

A second boost actuator appears on engines with two chargers, either one per cylinder bank or in a staged layout where a high-pressure and a low-pressure stage share the work. BorgWarner's two-stage patent describes a valve that shifts exhaust gradually from the small to the large turbine; its setting decides which stage does the work. U02AD is stored when this B actuator falls silent on the bus while A may still respond. No manufacturer documents U02AD publicly. A Ford two-stage patent shows a typical failsafe: bypass valve fully open, wastegate shut and torque capped so the low-pressure charger cannot overspeed or surge, chiefly at altitude. CARB treats such actuators as monitored boost components. Expect a MIL and limited power.

Likely causes

Damaged plug or harness at actuator B, heat-aged insulation
Supply or ground of actuator B interrupted
Electronics of actuator B failed
Replacement actuator not matched or not set up for position B

Symptoms

  • Check engine lamp
  • Weak pull in the speed range where the second stage normally takes over
  • Engine power limited

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–2,500
Time0.5–5 h

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

Parts involved

boost control module bvehicle bus wiring

Related codes

U02ACU010DU02B0P00B0P004A

References: patents.google.com, patents.google.com, law.cornell.edu.