C056A

Code

Generic C — Chassis

Brake Booster Pressure Sensor Power Supply Circuit

Brand: Generic

Type: C — Chassis

Views: UK: 20 EN: 45 RU: 23

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Page language: EN

Causes

Blown fuse or fusible link for sensor/ABS/BCM power
Damaged or corroded sensor connector or pins
Open, short to ground, or short to battery in sensor power or ground circuit
Faulty brake booster pressure sensor
Faulty ABS/Brake/Powertrain control module providing reference voltage
Wiring harness damage (chafing, rodent damage, water intrusion)

Symptoms

Brake/ABS warning lamp illuminated
Reduced or altered brake assist feel (harsher or longer pedal travel) on some systems
ABS/traction control may be disabled or show faults
Fault stored in vehicle control module and possible limp or degraded mode for brake functions
Possible diagnostic trouble codes for related systems

What to check

Read and record freeze frame and full scan-tool data for fuel, battery voltage, and related codes
Visual inspection of wiring and connectors at the brake booster pressure sensor and associated harness for damage or corrosion
Check related fuses and fusible links for continuity and correct rating
Backprobe sensor connector with harness intact and measure reference voltage, ground continuity, and signal
Wiggle test the harness and connector while monitoring the signal/voltage for intermittent faults
Measure voltage at the battery and compare to sensor reference during engine off and running conditions

Signal parameters

Typical reference (sensor supply) voltage: 5.0 V nominal (expect ~4.75–5.25 V); confirm with OEM data
Sensor ground: near 0 V, chassis-to-sensor ground continuity less than 1 ohm preferred
Signal output: typically a 0.5–4.5 V proportional range depending on vacuum/pressure (vehicle-specific)
No large voltage spikes or dropouts during normal operation or with key ON/engine running
Short to battery: supply or signal pinned to ~12 V; short to ground: supply or signal pinned near 0 V

Diagnostic algorithm

Retrieve freeze frame, read all stored codes and note related codes (ABS, ECM, BCM, U-codes).
Perform a visual inspection of the sensor, connector, and harness at the brake booster for damage, corrosion, or water entry.
Check applicable fuses/fusible links for the brake/ABS sensor and replace if blown. Verify fuse circuit power with a meter.
With the connector attached, backprobe the reference (supply), signal, and ground pins. Verify reference voltage (typically ~5 V) with key ON and engine running.
Measure sensor ground to chassis ground for low resistance (
Wiggle the wiring and connector while watching voltages and monitoring live data for intermittent changes.
If reference or signal voltages are out of range, disconnect the sensor and measure harness pin voltage/resistance to check for an open or short to power/ground. Use an ohm-meter to check continuity to the control module pin per wiring diagram.
If wiring and power/ground are good, swap or bench-test the brake booster pressure sensor per OEM instructions (or substitute known-good sensor) and recheck the circuit.
If the sensor and wiring check good but fault remains, inspect/replace the controlling module or repair module grounds only after confirming wiring integrity and consulting OEM procedures.
Clear codes and perform a road test or actuator/self-test to confirm repair. Re-scan for reoccurrence.

Likely causes

Loose/corroded connector at the brake booster pressure sensor
Open or shorted power/ground wire to the sensor
Blown fuse or fusible link supplying the sensor
Failed brake booster pressure sensor
Intermittent wiring fault (pinched/rodent)
Faulty control module (less common) or poor ground

Fault status

⚠️ Status

Stored when the control module detects the brake booster pressure sensor power supply circuit out of expected range (open/short/intermittent). May illuminate ABS/BRAKE lamps and disable related functions until the fault is corrected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours