C105B — Actuator Circuit - Group B

Causes

• Open or short in the actuator wiring harness (Group B)
• Corroded, bent or loose connector pins at the actuator or module
• Failed actuator (motor, solenoid or position sensor)
• Blown fuse or faulty relay supplying the actuator circuit
• Poor chassis or module ground
• Control module (ECU) output driver fault or internal failure

Symptoms

• Related system warning lamp illuminated (ABS/ESC/traction/other module message depending on vehicle)
• Loss or reduction of the affected function (e.g., valve not operating, motor not moving, diminished control)
• Humming, clicking or no noise from actuator when system commands movement
• Intermittent operation or fault returns after clearing codes
• Possible limp/limited functionality message

What to check

• Read freeze-frame and full fault list with a capable scan tool; note any related DTCs or communication faults
• Visually inspect actuator and wiring harness for damage, corrosion, pinch points and water entry
• Check relevant fuses and relays for proper condition and operation
• Verify proper battery voltage at the actuator power feed connector with key on (typically ~12 V)
• Check ground continuity from actuator ground pin to chassis (near 0 ohms)
• Measure actuator resistance and compare to service manual specification

Signal parameters

• Supply voltage to actuator: ~11–14 V with ignition ON (vehicle battery voltage)
• Control signal: may be switched +12 V or PWM; expected duty cycle varies by command — refer to factory data
• Ground resistance: near 0 Ω between actuator ground and chassis (typically
• Actuator coil/motor resistance: typically low ohms to low hundreds of ohms depending on actuator type — compare to factory spec
• Typical current draw: small solenoids 0.1–2 A, motors may draw higher under stall conditions — use service values

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