Chassis, generic

C05AD Brake Blending System Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

C05AD is the overall check of a blended brake: does the hydraulic pressure built by wire match what the controller asked for? GM's 2016 and 2019 hybrid tables (brake module BSC1) compare actual and target boost-piston pressure, for the by-wire side as well as the master cylinder side: more than 4,000 kPa too high points to a false high sensor value, more than 1,500 kPa too low to a low sensor value, an empty accumulator, a weak pump, air or a leak. It sets within 0.5–1 s, Type A with MIL. GM proves the repair by driving to about 25 mph and braking gently at around 3,000 kPa rear pressure twice. Bosch notes that blending generator and hydraulic braking is a core job of brake-by-wire, and Ford Otosan's patent compensates regeneration gaps with friction braking.

Likely causes

Brake pressure sensor reading too high or too low
Low accumulator pressure or weak hydraulic pump
Air in the hydraulic circuit after service
External or internal leak in the brake hydraulics

Symptoms

  • Brake warning and check engine lamps
  • Soft or inconsistent pedal, braking stronger or weaker than expected
  • Regenerative braking reduced

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–3,000
Time0.5–4 h

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

Parts involved

brake blending systembrake pressure sensor

Related codes

C05ABC05ACC058FC0571C05B0

References: gsi.ext.gm.com, gsi.ext.gm.com, bosch-mobility.com, patents.google.com.