C0571

Code

Generic C — Chassis

Brake Pressure Sensor C Circuit Low

Brand: Generic

Type: C — Chassis

Views: UK: 26 EN: 78 RU: 24

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ABS and/or traction control warning lamp illuminated
Brake system warning lamp in some vehicles
Possible reduced ABS/traction control functionality (limited braking control during ABS events)
Diagnostic trouble code stored; drivability often unaffected in normal braking (unless module disables functions)
Unusual behavior during ABS activation or valve operation

Retrieve freeze-frame data and stored codes with a scan tool; note accompanying ABS/traction codes
Visual inspection of sensor C wiring harness, connectors and ABS module connector for damage, corrosion or water ingress
Check vehicle battery voltage and main fuses for ABS/ESC circuits
Backprobe sensor connector with ignition ON to measure supply, signal and ground
Wiggle test harness while monitoring live data for intermittent changes
Inspect brake fluid area near sensor for leaks or contamination

Typical sensor topology: 3-wire pressure transducer — reference (usually +5V), signal (0.5–4.5V proportional to pressure), and ground
Expected reference/supply at sensor with ignition ON: approx. 5.0 V (validate with vehicle-specific data)
Signal output at rest: typically ~0.5–1.5 V; with increasing pressure signal rises toward ~4–4.5 V (vehicle-specific values vary)
Circuit low indication: signal voltage near 0.0–0.2 V or significantly below expected idle value
If signal reads battery voltage or >4.8 V, suspect short to battery or supply fault

Connect a professional scan tool and confirm C0571 and any related codes; record freeze-frame and live sensor data.
Perform a visual inspection of the brake pressure sensor C connector and harness for damage, corrosion, loose pins, or moisture; repair as needed.
With ignition ON (engine off), backprobe the sensor connector: verify reference voltage (~5V), ground continuity, and measure signal voltage. Note readings at idle (no brake pressure).
Apply brake pressure (carefully; have assistant press pedal or use a calibrated pressure source) while watching live signal: signal should rise smoothly. If signal remains low or stuck near 0 V, continue.
If signal is low, disconnect the sensor and measure continuity from the signal wire to chassis ground. If continuity to ground is present, isolate and repair short in wiring. If no short, inspect connector for shorted pin to ground.
If wiring checks OK, measure sensor resistance or compare signal behavior when sensor is bench-tested (if removable) or replace with known-good sensor per vehicle procedure.
If a new/known-good sensor does not restore correct signal, inspect ABS/ESC module connector and module grounds; test module outputs and replace module only after verifying wiring and sensor are good.
After repairs, clear codes and perform a road test or ABS activation routine to confirm the fault does not return.