C05B7: Brake Booster Temperature Sensor C Circuit Intermittent/Erratic
Intermittent signal from brake booster temperature sensor C. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
What C05B7 means
C05B7 is a generic OBD-II chassis code in the ABS & brakes group. In plain English: the computer found an electrical fault in that circuit: an open, short or bad connection, or a failed component.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Required
Get it fixed
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Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
- 01Connector looseMost likely
- 02Connector with intermittent contact under vibrationLess likely
- 03Harness routed against vibrating componentLess likely
Can I drive with C05B7?
Drive carefully and get it checked soon.
Normal hydraulic braking usually still works, but ABS, stability control or brake assist may be off. Leave extra stopping distance, especially on wet or icy roads. If the pedal feels soft or the red brake light is on, stop driving.
Why we rate it urgent
- ABS or brake assist may be disabled
- Turns on the check engine light
- Needs a drive cycle to confirm a repair
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose C05B7
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just C05B7. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for P25C8. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Test the circuit
Inspect the wiring and connector at the brake booster temp sensor c for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Connector loose; connector with intermittent contact under vibration; harness routed against vibrating component. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and complete a full drive cycle (cold start, idle, steady highway cruise, deceleration). The code is fixed when the related readiness monitor completes without it returning.
C05B7 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- Brake booster temp sensor C
C05B7 FAQ
What does C05B7 mean?
C05B7 means “Brake Booster Temperature Sensor C Circuit Intermittent/Erratic”. Intermittent signal from brake booster temperature sensor C. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
Is C05B7 serious? Can I keep driving?
We rate C05B7 as urgent severity. Drive carefully and get it checked soon. Normal hydraulic braking usually still works, but ABS, stability control or brake assist may be off. Leave extra stopping distance, especially on wet or icy roads. If the pedal feels soft or the red brake light is on, stop driving.
What causes C05B7?
The most common causes, from most to least likely: Connector loose; Connector with intermittent contact under vibration; Harness routed against vibrating component. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix C05B7?
Typical labor is about $65–$375 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix C05B7 myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will C05B7 clear itself?
Once the fault is fixed, the check engine light usually goes off by itself after the system passes its self-test over several drive cycles. Clearing the code with a scan tool resets readiness monitors, so an inspection station may turn you away until a full drive cycle is completed.