Chassis, generic

C056B Brake Pressure Sensor A Intermittent/Erratic

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modePossible

C056B means the signal from brake pressure sensor A drops out or jumps for short moments instead of being steadily wrong. Ford's hybrid summaries (2015–2019) name two triggers: a checksum error in the digital data coming from the sensor for 70 ms, or a commanded control signal that does not show up at the sensor within 70 ms; the check runs only with a healthy sensor supply (no C056A). Ford's ABS module stores the same event as C0044. Saab's 2011 9-5 shows the consequence of an erratic pressure signal under its own code C0131: ABS, hill start assist, stability and traction control are disabled for the rest of the ignition cycle. Shaking the harness while watching live data helps find the loose contact.

Likely causes

Loose or corroded contact in the pressure sensor connector or harness

Disturbed digital sensor line, e.g. damaged shielding or poor ground

Sensor electronics failing intermittently, often in the hydraulic unit

Brief dips in the 5 V sensor supply

Symptoms

ABS and stability lamps that come and go
Stability control or hill start assist off until next start
Regenerative braking reduced on hybrids

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 a

Related codes

C056C C053D C0560 C056A C0044

References: fordservicecontent.com, saabwisonline.com, patents.google.com, bosch-mobility.com.