C05C8

Code

Generic C — Chassis

Brake Pressure Sensor F Circuit/Open

Brand: Generic

Type: C — Chassis

Views: UK: 21 EN: 40 RU: 21

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Page language: EN

Causes

Open or broken wiring between sensor and ABS/ECU
Corroded, loose or damaged connector/pins at sensor or module
Failed brake pressure sensor (internal open)
Short to ground or to battery (intermittent high resistance)
Blown fuse or poor ground related to the sensor power/return
Water intrusion or contamination at connector

Symptoms

ABS warning light and/or traction control light ON
Brake system warning lamp may illuminate
ABS functionality reduced or disabled
Possible reduced braking system performance under ABS regulation
Stored fault code(s) and freeze frame data in ABS module
Intermittent ABS activation or pump motor running unexpectedly

What to check

Scan ABS/Brake module for C05C8 and other related codes; record freeze-frame and live data
Visual inspection of sensor, harness, and connectors for damage, corrosion, or water
Check fuses and power/ground circuits for the ABS/brake sensor system
Backprobe sensor connector and watch live voltage/resistance while operating brake
Wiggle test wiring while monitoring live data to reproduce fault
Measure continuity and resistance between sensor connector and ABS module connector

Signal parameters

Typical sensor signal: 0–5 V analog (common: 0.5–4.5 V span); open circuit ≈ no voltage or 'OL'
Reference power (if present) ≈ 5 V regulated from module or ECU
Sensor ground: near 0 V; poor ground shows elevated voltage/noise
Expected resistance (if two-wire): manufacturer-specific; open circuit = infinite Ω
Signal should change smoothly with applied brake pressure (no stepping or dropout)
If CAN/serial sensor: LIN/CAN message loss or checksum error may be present

Diagnostic algorithm

Read and record all ABS/Brake codes and freeze-frame data with a scan tool.
Inspect sensor connector and harness for corrosion, bent pins, damage, or fluid contamination. Repair as needed.
Verify power and ground to the sensor connector with key on: check for proper reference voltage and good ground.
Backprobe the signal pin and watch live data/voltage while slowly operating the brake system (or using a pressure tool if accessible). Look for a smooth, proportional change.
If no signal, measure continuity between sensor signal pin and ABS module pin. Repair any open circuits (repair/replace wiring or connectors).
If continuity to module is good but signal absent or abnormal, disconnect sensor and measure sensor resistance/voltage per manufacturer spec. Replace sensor if out of specification.
Perform wiggle test on wiring while monitoring signal to detect intermittent faults. Re-pin or repair connector if intermittent.
Check for related fuses and shared grounds; clean/repair grounds as necessary.
After repairs, clear codes and perform road or bench test to ensure code does not return and ABS operates normally.
If wiring and sensor check good and code persists, consider module input circuit fault and refer to module replacement/repair procedures.

Likely causes

Wire chafed or broken at suspension/steering pivot or near master cylinder
Connector corroded or pins pushed out at sensor harness
Sensor failed due to contamination or impact
Poor ground or shared ground point corroded
Recent repair work disturbed harness/connector

Fault status

⚠️ Status

Brake Pressure Sensor F Circuit/Open — control module detects an open or high-resistance condition in the Brake Pressure Sensor F circuit. Check wiring, connectors, power/ground, and the sensor.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours