Chassis, generic

C0641 Brake Pressure Sensor K Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Brake pressure sensor K has an open circuit. Because the letter I is skipped in this series, K stands for a tenth pressure sensor, which is rare in cars; no carmaker publishes C0641 and the assignment is unknown. Heavy vehicles show how many pressure inputs one brake ECU can have: Bendix's EC-80 ESP reads a brake demand sensor in each of the two air circuits plus a load sensor and keeps a separate open-or-shorted code for each; ESP is then switched off while ABS and traction control stay active. In passenger cars the sensor often plugs straight into the module, as in a Kelsey-Hayes design, which removes harness opens but not contact faults. Honeywell notes that the resulting level after an open depends on whether the input has a pull-up or a pull-down resistor.

Likely causes

Poor contact between sensor and module or harness connector
Open conductor where an external harness is used
Internal open in sensor K

Symptoms

  • ESC or ABS warning lamp on
  • Stability control off, basic ABS may remain available

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–1,500
Time0.5–3 h

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

Parts involved

brake pressure sensor ksensor wiring

Related codes

C0642C0643C0644C063DC0635

References: static.nhtsa.gov, patents.google.com, prod-edam.honeywell.com.