C05B5

Code

Generic C — Chassis

Brake Booster Temperature Sensor C Circuit/Open

Brand: Generic

Type: C — Chassis

Views: UK: 22 EN: 32 RU: 33

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Page language: EN

Causes

Open circuit in sensor wiring (broken wire, disconnected connector)
Corroded or pushed-out connector pins
Failed temperature sensor (open or internally damaged)
Poor or lost ground or reference voltage to the sensor
ECU/ABS module input fault
Water or contamination in connector or sensor

Symptoms

Brake/ABS warning lamp or fault indicator illuminated
Stored chassis DTC C05B5 (Brake Booster Temperature Sensor C Circuit/Open)
Possible loss of temperature-dependent brake booster features or reduced assist
Intermittent faults when wiring is moving or wet
No driveability symptoms may be present except warning indicators

What to check

Retrieve freeze-frame and live data for Brake Booster Temp Sensor C using a scan tool
Visually inspect sensor, connector, and wiring for damage, corrosion, contamination or water ingress
Check for secure connector mating and correct terminal condition (no pushed-out pins)
Measure reference voltage and ground at the sensor connector with ignition ON
Measure sensor resistance or voltage output at the sensor and at the module connector (compare to expected values)
Perform continuity check from sensor pin to module pin to verify no open circuit

Signal parameters

System reference voltage: typically ~5.0 V (vehicle-specific)
Sensor signal voltage range: generally 0–5 V (open-circuit often reads near reference or >4.5 V; short near 0 V) — exact polarity depends on sensor type
Thermistor resistance: varies with temperature (example NTC ~2 kΩ–100 kΩ across typical temperatures); open-circuit = infinite resistance
Expected idle/ambient temp values available from factory data or service manual — compare live-data temp reading to ambient conditions

Diagnostic algorithm

Read freeze frame and live data for Brake Booster Temperature Sensor C. Note present value, last recorded value and any related codes.
Perform visual inspection of the sensor and harness from the sensor to the ABS/PCM module. Look for damage, chafing, corrosion, or water intrusion.
With ignition ON (engine OFF), backprobe the sensor connector. Verify reference voltage (usually ~5 V) and good ground on the appropriate pins per vehicle wiring diagram.
Measure the sensor output voltage at the sensor connector while monitoring live-data. Compare to expected voltage for ambient temperature. If the sensor is a thermistor, measure resistance across sensor terminals and compare to expected resistance chart.
If the sensor reads open (infinite resistance) or the voltage is out-of-range, disconnect the sensor and measure continuity and resistance of the sensor harness back to the module connector. Repair any open or shorted wiring.
Repair or replace corroded/pushed terminal pins, and ensure proper connector mating and sealing. Clean and apply dielectric grease where appropriate.
If wiring and connectors check good, disconnect the harness at the control module and measure continuity and pin voltages at the module connector to confirm the module sees the signal and reference.
If the sensor and wiring test good at the module but the module input does not, consider control module fault — confirm with manufacturer diagnostics before replacement.
After repairs, clear codes, perform functional test or road test, and monitor live data to ensure the sensor reading is stable and within expected range and the DTC does not return.

Likely causes

Disconnected or damaged harness/connector at the temperature sensor
Failed temperature sensor (open element)
Corroded connector pins or poor ground
Short/open in wiring between sensor and control module
Fault in control module input (less common)

Fault status

⚠️ Status

Brake Booster Temperature Sensor C circuit open or high resistance detected. Sensor signal missing or out of range; check sensor, wiring, connectors and module input.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours