C05B7

Code

Generic C — Chassis

Brake Booster Temperature Sensor C Circuit Intermittent/Erratic

Brand: Generic

Type: C — Chassis

Views: UK: 20 EN: 33 RU: 37

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged, chafed or pinched wiring in the sensor harness
Corroded, loose or contaminated connector/pins at the sensor or module
Faulty Brake Booster Temperature Sensor (thermistor)
Poor or broken ground or reference supply to the sensor
Intermittent short to voltage or ground caused by movement or moisture
Faulty ABS/Brake control module or intermittent module connector

Symptoms

ABS/brake warning lamp or related dash warning may illuminate intermittently
Stored diagnostic trouble code C05B7 and possible driveability or ABS self-test warnings
Intermittent or inconsistent brake pedal feel reported by driver (if control strategies change)
Live data for Brake Booster Temp C shows jumping, implausible or frozen values
Failing brake system self-checks during key-on or driving

What to check

Connect a scan tool and record DTC, freeze frame, and live data for Brake Booster Temperature C while key on and during a short drive
Visually inspect sensor connector, pins and harness for corrosion, moisture, damage or loose terminals
Wiggle test harness and connector while watching live data to reproduce intermittent behavior
Backprobe connector and verify reference voltage (if present), signal voltage and ground integrity with key on
Measure sensor resistance at ambient temperature and compare to specification (or note thermistor response while warming/cooling)
Perform continuity and resistance checks for wiring between sensor and control module; check for shorts to battery or ground

Signal parameters

Typical sensor type: negative-temperature-coefficient (NTC) thermistor (resistance changes with temperature)
Common reference voltage to sensor circuits: ~5.0 V (vehicle-specific)
Expected signal voltage range: ~0.1–4.9 V depending on temperature (vehicle-specific)
At 20–25 °C the signal is commonly around mid-scale (example ~2.5 V) — consult OEM specification for exact values
Resistance range across full temperature span often falls in the broad range of ~1 kΩ to 100 kΩ depending on design — check vehicle spec

Diagnostic algorithm

Read and record DTCs, freeze frame and live data with a capable scan tool. Note when fault sets and any related codes.
Visually inspect sensor, connector, and harness for contamination, bent pins, corrosion, damage or water ingress. Repair obvious issues.
With key on, monitor live data for Brake Booster Temp C. Perform a wiggle test of harness and connector to try to reproduce the erratic reading.
Backprobe the sensor connector. Verify reference voltage (if used), signal voltage behavior and a good ground. Compare to expected ranges in service data.
Remove sensor (if serviceable) and measure its resistance at known ambient temperature. Heat or cool sensor slightly (hair dryer/ice) and observe resistance/voltage change to confirm thermistor response.
Perform continuity and short-to-power/short-to-ground tests on wiring between sensor and module. Repair any open or chafed wiring, and replace damaged connectors or terminals.
If wiring and sensor check OK but intermittent persists, scope the signal line to capture transients/noise during reproduction. Use scope to detect high impedance or intermittent opens.
Replace the sensor if it fails resistance/response checks or if connector is internally damaged and cannot be reliably repaired.
After repair, clear DTCs and perform functional test/road test. Re-scan to confirm code does not return under normal operation.
If fault returns and wiring/sensor are confirmed good, consider control module connector inspection or module testing/repair and review technical service information.

Likely causes

Loose or corroded connector at the sensor
Broken or intermittent wire in harness (inside loom, near rub points or connectors)
Failed temperature sensor element (open/short or erratic thermistor)
Poor ground or supply voltage intermittent due to corrosion or damaged pin