Chassis, generic

C064C Brake Pressure Sensor M Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

Sensor M stays inside its electrical window, but the pressure it reports is not believable. Trailer EBS shows an active test: when the control pressure exceeds 0.3 bar, WABCO's modulator switches its redundancy valve to reservoir pressure and starts EBS braking; during the stop it briefly switches back and uses its internal actual-pressure sensors to confirm that pneumatic pressure is present, otherwise it changes to purely pneumatic braking. Kelsey-Hayes lists in-range checks for hydraulic sensors: high pressure lasting unusually long, or high pressure while the brakes are not applied. No carmaker documents C064C or says which sensor is M. Possible causes: drift, a sticking valve, a leak, contamination in the sensor port.

Likely causes

Sensor reading drifted from the true pressure
Valve in the measured circuit not switching as commanded
Contamination or air at the sensor port

Symptoms

  • Warning lamp on after a brake application
  • Braking switched to a backup mode with less precise pressure control

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–2,000
Time0.5–4 h

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

Parts involved

brake pressure sensor m

Related codes

C0649C064AC064BC0648C0650C0644

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