C05B6

Code

Generic C — Chassis

Brake Booster Temperature Sensor C Circuit Range/Performance

Brand: Generic

Type: C — Chassis

Views: UK: 18 EN: 27 RU: 19

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Page language: EN

Causes

Open or short in the sensor wiring (signal, power, or ground).
Corroded, loose, or contaminated connector at the sensor or module.
Failed or degraded brake booster temperature sensor (thermistor or temperature element).
Water intrusion or contamination inside the brake booster or connector.
Faulty ABS/brake control module or interrupted reference supply/ground.
Intermittent harness damage (chafing, pinched, rodent damage).

Symptoms

Brake system warning light or ABS warning (depending on vehicle).
Diagnostic trouble code stored; possible limited brake system diagnostics.
Noisy or inconsistent brake booster behavior under certain conditions (rare).
Possible degraded cruise/regen (if system uses temp data) or stored related codes.
Intermittent faults that may clear after drying or reconnecting.

What to check

Read freeze frame and live data with a scan tool: watch brake booster temp signal and compare to ambient/engine temp.
Perform a visual inspection of the sensor, connector, and wiring for damage, corrosion, or contamination.
Check for TSBs or vehicle-specific service information related to this code.
Clear code and attempt to reproduce with live data monitoring to capture behavior.
Check related fuses and ensure proper power/ground to brake control module.

Signal parameters

Sensor type: typically a thermistor (NTC or PTC) providing a voltage or resistance proportional to temperature.
Typical signal voltage range: about 0.5–4.5 V (varies by manufacturer).
Typical resistance at ~25°C: commonly in the 1 kΩ–10 kΩ range for NTC devices (manufacturer-dependent).
Expected behavior: smooth, monotonic change in resistance/voltage with temperature changes; no sudden jumps or flatlines.
Fault signatures: open circuit → near 0 V or very high resistance; short to ground → near 0 V; short to battery → near battery voltage; implausible values for ambient conditions.

Diagnostic algorithm

Retrieve DTC details and freeze frame with a scan tool. Note conditions when code set (temperature, vehicle state).
Visually inspect the brake booster sensor connector and wiring for damage, corrosion, loose pins, or water ingress. Repair as needed.
With ignition on (engine off) monitor live data: verify sensor voltage/resistance and compare to ambient/engine temperature. Look for erratic or stuck values.
Back-probe the sensor connector and measure signal voltage, reference power (if present), and ground continuity. Compare to expected ranges from manufacturer data or the signal_params guidance.
Measure sensor resistance (unplug sensor if required) at ambient temperature and, if possible, warm or cool the sensor slightly (hair dryer/ice pack) while watching resistance/voltage change; confirm monotonic response.
Perform a wiggle test on harness while monitoring live data to check for intermittent wiring faults. Repair any damaged wiring or connector terminals.
If wiring and connector are good, swap or bench-test the sensor (if available) or replace with a known-good sensor and re-scan.
If sensor replacement does not cure and wiring checks good, inspect/replace control module ground(s) and check module power/inputs. Consider module replacement only after exhaustive wiring/sensor verification.
After repair, clear codes and test drive or reproduce the conditions to confirm the code does not return.

Likely causes

Wiring harness open/short to battery or ground at sensor connector.
Connector corrosion or poor mating causing high resistance.
Failed temperature sensor (stuck high/low, erratic output).
Moisture inside connector or booster housing causing shorts.
Faulty module input or internal module fault (less common).

Fault status

⚠️ Status

Stored when the brake booster temperature sensor C circuit reports a signal outside its expected range, shows no response, or demonstrates implausible/erratic performance compared to other temperature inputs. May set a brake/ABS warning indicator or limit certain diagnostics depending on vehicle. Further testing required to isolate sensor, wiring, or module faults.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours