Chassis, generic

C064B Brake Pressure Sensor M Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Sensor M sits below its lower signal limit. Because modules often supply several pressure sensors together, a single low code can be the visible part of a wider fault: WABCO's trailer modulator powers all active sensors jointly, so a short on one sensor supply can pull others down too, and codes for neighbouring letters may then appear at the same time. In an ESP block, Bosch describes each sensor with four contacts, two for supply and two for the analog pressure signal, which makes a shorted or contaminated spring contact a plausible cause. GM's 2019 brake module flags its secondary circuit pressure sensor low under 4.61 % of supply for 100 ms; no maker publishes C064B itself. Check the shared supply before replacing sensor M.

Likely causes

Shared sensor supply shorted, pulling several sensors low
Signal line or contact of sensor M shorted to ground
Sensor element failed

Symptoms

  • Warning lamp on, possibly with further pressure sensor codes
  • Electronic brake functions reduced to a fallback mode

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

C0649C064AC064CC0647C064FC05C9

References: wabco-customercentre.com, patents.google.com, gsi.ext.gm.com.