Chassis, generic

C064A Brake Pressure Sensor M Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C064A: the voltage from sensor M exceeds what any valid pressure would give. On WABCO's Trailer EBS D the brake pressure sensor of an extra EBS relay valve, for example on a drawbar trailer's front axle, draws its supply from the trailer modulator and returns its actual value as an analog signal; all active sensors share supply outputs that are protected against short circuits. A short from that supply to the signal pin therefore drives the reading to the top. Kelsey-Hayes adds the opposite path: an open circuit lets a bridge output rise to supply level, so a high code does not exclude a broken wire. No passenger-car maker documents C064A. With the channel discarded, the system falls back to reduced functions.

Likely causes

Signal pin shorted to the sensor supply or battery voltage
Open sensor ground or signal line letting the input float high
Sensor output stuck at its upper limit

Symptoms

  • Brake or ABS warning lamp on
  • Load-dependent or electronic pressure control disabled

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,600
Time0.5–3 h

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

Parts involved

brake pressure sensor msensor wiring

Related codes

C0649C064BC064CC0646C064EC0642

References: wabco-customercentre.com, patents.google.com.