Chassis, generic

C05A7 ABS Pump Motor Supply Voltage B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Supply B of the pump motor reads below its lower limit. The pump motor draws high current, so a weak 12 V battery, corroded terminals, a fuse holder with high resistance or a poor ground show up first under load. No maker documents C05A7 publicly. Published low-voltage checks for the single feed give a sense of scale: Ford hybrids flag the pump circuit if it is under 7.3 V for 1.8 s while running (C052B), Mitsubishi's Outlander PHEV stores C1056-16 at 10 V or less, and an AlliedSignal patent, now Bosch, sets a separate fault if the motor sees less than about 7 V at switch-off. For a motor with two power modules on their own inputs, as patented by Hyundai Mobis, one weak side can be dropped. Circuit A has its own code C055B.

Likely causes

Weak or discharged 12 V battery
Corroded terminal, fuse holder or ground in the B feed
Charging system not keeping up (alternator or DC/DC converter)

Symptoms

  • ABS/ESC lamp on, often after cold starts or long standstill
  • Pump motor running audibly slower during self-test

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–400
Time0.3–2 h

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

Parts involved

abs pump motor supply b

Related codes

C05A5C05A6C05A8C05A9C055BC0564

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