Chassis, generic

C05A1 Brake Pressure Sensor E Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

This code points to an interrupted circuit of sensor E: a broken signal, 5 V supply or ground wire, or a connector that has lost contact. No maker documents C05A1 publicly. Whether an open is recognised as such or as low or high depends on the input circuit, which is why many systems book it under C059F or C05A0 instead. Honeywell specifies that with an external pull-up resistor a power or ground loss drives the output high, with a pull-down low. A Denso patent adds a check for creeping contact resistance, which produces in-between voltages that such resistor schemes miss: the supply is briefly raised so the sensor outputs a fixed test voltage. Bosch's EBS monitors each of its pressure sensors separately. Check connector and wiring before condemning the sensor.

Likely causes

Corroded or loose connector at the sensor or hydraulic unit
Broken signal, supply or ground wire
Internal open circuit in the sensor

Symptoms

  • ABS/ESC warning lamp on, possibly coming and going
  • Stability control and brake assist switched off

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,500
Time0.5–3 h

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

Parts involved

brake pressure sensor esensor wiring

Related codes

C059FC05A0C05A2C05C8C0577

References: prod-edam.honeywell.com, patents.google.com, bosch-motorsport.com.