Chassis, generic

C05A6 ABS Pump Motor Supply Voltage B Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C05A6 says the second pump motor feed, supply B, carries more voltage than allowed. Overvoltage strains the motor and above all the transistors that switch it; gate driver ICs for brake motors such as TI's DRV8305-Q1 therefore watch their supply and raise an overvoltage warning in the mid-30 V range. Typical causes are a faulty alternator or DC/DC converter regulator, jump-starting or charging at too high a voltage, or a measuring fault in the module. No maker documents C05A6 publicly. As an orientation, Mitsubishi's 2023 Outlander PHEV specifies 10–16 V for the motor feed and stores C1056-17 once the brake unit's supply reaches 16 V within 1 s. Where the motor has two power modules on separate inputs, as in a Hyundai Mobis patent, the faulty side can be disabled while the other keeps working.

Likely causes

Alternator or DC/DC converter regulating too high
Jump start or battery charger with excessive voltage
Voltage measurement fault in the brake module

Symptoms

  • ABS/ESC warning lamp on, possibly with other overvoltage codes
  • Very bright lights or battery warning if charging is the cause

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–900
Time0.3–3 h

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

Parts involved

abs pump motor supply b

Related codes

C05A5C05A7C05A8C05A9C055AC0565

References: ti.com, mitsubishitechinfo.com, patents.google.com.