Chassis, generic

C05A5 ABS Pump Motor Supply Voltage B Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Supply B is a second power feed for the pump motor of the brake unit; C05A5 reports it as missing or open. A second feed is found where the motor or its drive is built redundantly. Hyundai Mobis patents a brake motor with two windings, each with its own power module and own supply input from the battery; if one side fails it is shut off and the other carries the full current. Ipgate describes a brake-by-wire drive with two three-phase strands and electronics on two redundant voltage supplies. No maker documents C05A5 publicly. Mitsubishi's 2023 Outlander PHEV shows the usual single-feed layout: 60 A fusible link to the motor, 10–16 V at the connector. Feed A has its own code C052F. Depending on design, the pump runs on with reduced power or brake functions are cut back.

Likely causes

Blown fuse or fusible link in the B supply
Open wire or loose terminal in the B feed to the brake unit
Internal fault in the second power stage of the brake module

Symptoms

  • ABS/ESC or brake system warning on
  • Reduced pressure build-up or loss of redundancy message

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€20–1,500
Time0.3–3 h

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

Parts involved

abs pump motor supply bfuse

Related codes

C05A6C05A7C05A8C05A9C052F

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