Chassis, generic

C0650 Brake Pressure Sensor N Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

Sensor N reports a pressure that is electrically valid but disagrees with the commanded or expected value. WABCO's truck EBS runs a matching test: with a defined magnetic flux in the proportional valve a minimum brake pressure must build up at the front axle brakes, or at the valve that controls the trailer, and when the vehicle brakes via pneumatic backup the rear axle must reach a set minimum once the front exceeds a threshold. A Kelsey-Hayes patent avoids a second complete sensor by putting two sensing elements on one diaphragm and flagging a fault when their readings differ beyond a threshold. Neither source uses the code; C0650 and the letter N are not assigned publicly. Causes: drift, valve faults, leaks, air.

Likely causes

Sensor N reading drifted
Valve or modulator not building the commanded pressure
Leak or air in the measured circuit

Symptoms

  • Warning lamp on after braking
  • Pressure control falls back to an emergency mode

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 n

Related codes

C064DC064EC064FC0648C064CC0644

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