Chassis, generic

C0643 Brake Pressure Sensor K Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Sensor K reports less voltage than any valid pressure would give. Bendix's truck ESP treats brake demand and load sensors individually and, if one of them fails, disables only ESP while ABS and traction control carry on; this graded reaction shows why the code may leave basic ABS working. GM's 2016 hybrid module compares the wheel pressure signal with ground and sets its low code under 0.3 V within 0.1 s. Denso points out that a broken supply wire reads exactly like this when the module pulls its input down, so a low code does not rule out an open. Which sensor K would be is not published by any carmaker. GM's PIP5094 keyword list contains C0643 from its old numbering, unrelated to this sensor.

Likely causes

Signal line shorted to ground
Broken sensor supply read as 0 V through the input pull-down
Sensor K without output

Symptoms

  • ESC lamp on, ESC switched off
  • ABS and traction control may keep working

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 ksensor wiring

Related codes

C0641C0642C0644C063FC0575

References: static.nhtsa.gov, gsi.ext.gm.com, patents.google.com, static.nhtsa.gov.