Code
C0047
HYUNDAI
C — Chassis
Brake Booster Pressure Sensor (Subfault)
Views:
UK: 25
EN: 39
RU: 28
AI status
Completed
Completed
100%
Causes
- Faulty Brake Booster Pressure Sensor
- Open/short or intermittent wiring between sensor and ABS/BCM/ECU
- Poor or corroded connector or terminal
- Blown fuse or poor ground/reference supply to sensor
- Vacuum leak or mechanical failure in the brake booster
- Intermittent ECU/module input or software fault
Symptoms
- ABS / ESC or brake warning lamp illuminated
- Brake assist reduced or felt as a harder brake pedal
- Longer stopping distances or inconsistent pedal feel
- MIL or other related warning messages in dash
- Possible engine idle changes if large vacuum leak is present
- Fault may be intermittent (comes and goes)
What to check
- Read and record freeze frame and all stored ABS/BCM/ECU codes with a capable scan tool
- Inspect sensor connector and wiring for damage, corrosion, or moisture
- Backprobe sensor connector and verify reference voltage (typically 5 V), signal voltage, and ground
- Wiggle harness and connectors while monitoring live data to reproduce the fault
- Measure sensor resistance/voltage and compare to OEM specification
- Perform vacuum test on brake booster (check for vacuum leaks) and operation of check valve
Signal parameters
- Typical sensor supply: reference 5 V (varies by model) — verify against OEM spec
- Signal output: typically in the 0.5–4.5 V range or 0–5 V range depending on sensor type (consult vehicle spec)
- Signal should change when engine vacuum changes or when brake booster load changes (engine off vs running, brake applied)
- Good ground continuity between sensor ground terminal and chassis ground
- No high resistance or intermittent connection on reference/signal/ground circuits
Diagnostic algorithm
- Connect a diagnostic scanner and confirm C0047 and any related codes. Record freeze-frame data.
- Visually inspect brake booster, sensor, connector, and wiring for obvious damage or moisture. Repair visible issues.
- With ignition ON, backprobe sensor connector: verify reference voltage, ground continuity, and signal voltage at rest. Compare to spec.
- Start engine and observe signal change with engine vacuum; have assistant apply brake pedal while monitoring live data. Note abnormal or no change.
- Wiggle wiring harness/connectors while watching live data and code status to find intermittent faults.
- If electrical checks are out of specification, isolate by checking continuity to ECU and grounds, repair short/open, then retest.
- If electrical circuits check OK, bench-test or replace sensor and recheck. Use OEM replacement if available.
- If sensor replacement does not clear the issue, inspect brake booster vacuum system (check valve, vacuum lines) for leaks and correct as needed.
- After repairs, clear codes and perform road/functional test to confirm no recurrence and proper brake assist operation.
- If fault persists, consider module diagnostic/repair or professional diagnosis with OEM-level wiring diagrams and tooling.
Likely causes
- Connector corroded or pin pushed out at sensor
- Sensor contaminated or internally failed
- Damaged harness (chafing, rodent chew, water intrusion)
- Weak or lost vacuum to booster producing out-of-range values
- Poor ground at sensor or at ECU body/chassis ground
Fault status
Status
Brake Booster Pressure Sensor subfault detected. Inspect sensor, wiring, and booster vacuum; repair and retest.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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