Chassis, generic

C05CF Brake Master Cylinder Piston Position Sensor B Circuit Range/Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Plausibility fault on channel B (GM: PTS2) while its signal is electrically in range. GM's integrated controller with pedal simulator runs the same checks on B as on A: more than 38 mm of travel, a step faster than 700 mm/s that disagrees with channel A and the simulator pressure model, or an offset beyond 2.5 mm, all with 100 ms and Type A. In the booster-type units the B offset with released pedal is limited to 0.9 mm (XT4) or +1.1/-1.5 mm (2023/2025 tables). Wards reported that this vacuum-free ZF system for GM full-size trucks reads the driver's braking wish from a pedal sensor, so a bad channel directly affects brake request. C05CC handles channel A, C05D0 the A/B comparison.

Likely causes

Offset of sensor B outside the allowed range
Loose contact causing implausible jumps on channel B
Sensor rod or mounting worn or bent

Symptoms

  • Malfunction indicator lamp and brake warning
  • Pedal feels different, assist may be reduced

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0.5–3 h

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

Parts involved

master cylinder pos sensor belectric brake booster

Related codes

C05CDC05CEC05CCC05D0

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, wardsauto.com.