Chassis, generic

C05A2 Brake Pressure Sensor E Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

Here sensor E delivers a voltage that is electrically valid but does not fit the braking situation: a drifting zero point, wrong gain or a value that disagrees with other pressure signals. No maker documents C05A2 publicly. The usual tests are known from related sensors. GM's hybrid brake controller learns each wheel sensor's zero while the pedal is released and flags an offset beyond ±1,500 kPa at once. A Bosch patent sets an offset fault when the compensation passes a limit, lights the ABS and ESC lamps and clears it only after a good check while driving. A Lucas/ZF patent opens the valves at standstill so all sensors see one pressure; with at least three of them the drifting one and its error can be identified. Trapped pressure, sensor drift or a ground offset are typical causes.

Likely causes

Sensor zero point or gain drifted with age or temperature
Residual pressure trapped in the circuit during the zero learn
Ground offset between sensor and module distorting the reading

Symptoms

  • ABS and ESC warning lamps on
  • Stability or regenerative brake functions reduced

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,800
Time0.5–4 h

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

Parts involved

brake pressure sensor e

Related codes

C059FC05A0C05A1C059EC05C5C0578

References: gsi.ext.gm.com, patents.google.com, patents.google.com.