Chassis, generic

C0645 Brake Pressure Sensor L Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0645 reports lost continuity in the circuit of brake pressure sensor L, the eleventh letter of the series because I is not used. That is far beyond a normal car: a Bosch patent names one, three or five sensors as the usual ESP layouts and calls five the current maximum. No carmaker publishes which sensor would carry the L. Where it does exist, the sensor is often clinched straight into the valve block, and Continental and Bosch both describe its four contacts (supply, ground, two signal pads) touching spring contacts on the module board instead of a harness. An open is then frequently a bent spring, a corroded pad or a crack inside the unit, not a broken wire. Expect the ESC and ABS lamps; ordinary braking is kept.

Likely causes

Spring contact between sensor and module board bent, dirty or corroded
Plug or harness of an externally mounted sensor without continuity
Internal interruption in sensor L

Symptoms

  • ESC and ABS warning lamps on
  • Pressure-based functions such as brake assist or hill hold unavailable

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–1,800
Time0.5–4 h

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

Parts involved

brake pressure sensor lsensor wiring

Related codes

C0646C0647C0648C0649C064DC0641

References: patents.google.com, patents.google.com, actronics.co.uk.