Chassis, generic

C0648 Brake Pressure Sensor L Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

Sensor L delivers an electrically valid signal whose pressure does not fit the situation. Commercial vehicle EBS shows how such a check works with many sensors: WABCO's tractor EBS has pressure sensors in the front axle relay valve, in each channel of the rear axle modulator and in the trailer control valve. During normal braking the left and right rear pressures must almost match, and a deviation beyond the permitted value is stored as a fault. Each sensor carries individual calibration data; in Continental's process they are matched to its serial number and stored in the module, so a mismatch after a repair could also appear as an offset. No carmaker documents C0648 or the letter L. Look for drift, trapped pressure, a sticking valve or a leak.

Likely causes

Sensor offset or gain drifted
Sticking valve, leak or trapped pressure in the measured circuit
Calibration data not matching the fitted sensor after a repair

Symptoms

  • ABS/ESC warning lamp on, sometimes only after several brake applications
  • Uneven or reduced electronic brake force distribution

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 l

Related codes

C0645C0646C0647C064CC0650C0644

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