Code
P05E009
BYD
P — Powertrain
Failure to validate brake pedal position sensor A and B
AI status
Completed
Completed
100%
Causes
- Failed or damaged brake pedal position sensor A or B
- Open, short or intermittent wiring between sensors and control module
- Corroded, bent or loose connector pins at the sensor or module
- Incorrect sensor alignment or mechanical binding at the pedal assembly
- Loss of reference voltage or ground to one or both sensors
- Software/firmware error or internal input-channel failure in the ECU/BCM
Symptoms
- Brake warning lamp or ABS/ESC warning lamp illuminated
- Cruise control may not engage or may be disabled
- Delayed or unexpected behavior of brake-related features (regenerative braking, brake lights)
- Driveability symptoms rare, but limp-home mode or reduced functionality possible
- DTC stored in ECU; related drive-data may show inconsistent pedal position readings
What to check
- Check for any additional DTCs and note freeze frame/live data with a scan tool
- Visually inspect the brake pedal sensor connectors and harness for damage, corrosion, pin push‑out, or rod/displacement interference
- Verify sensors are securely fastened and pedal linkage moves freely without binding
- Check for signs of recent work or aftermarket devices that could affect wiring (alarms, trackers)
- If vehicle has high-voltage systems (hybrid/EV), follow HV safety procedures before working near components
Signal parameters
- Reference supply typically 5 V (verify vehicle-specific spec) to both sensors; expected tolerance ±0.2–0.5 V
- Sensors may output a variable analog voltage proportional to pedal position (common range ~0.5–4.5 V) or complementary digital signals depending on design
- At rest (pedal released) typical outputs: sensor A ~0.5–1.0 V, sensor B ~0.5–1.0 V; at full travel outputs approach 4.0–4.5 V — compare both channels for correlated change
- If sensors are simple switches, expected states are ~0 V (ground) or ~5–12 V depending on circuit; both switches should change state at the same pedal position
- Continuity/impedance: open/infinite indicates broken conductor; short to 0 V or battery voltage indicates wiring short
Diagnostic algorithm
- Use a scan tool to read stored codes and monitor live brake pedal position A and B values while slowly moving the pedal. Note when/if signals diverge or go out of range.
- Visually inspect connectors and wiring from pedal sensors to module. Repair any damaged insulation or pins; reseat connectors.
- With ignition ON (engine off) and safe to probe, measure reference voltage at each sensor connector (should be ~5 V or vehicle-specified). If missing, trace back to ECU/fuse/relay.
- Measure sensor outputs while operating pedal. Verify both channels change smoothly and correlate. If one channel is stuck, open, or erratic, suspect that sensor or wiring to it.
- Backprobe harness for continuity from sensor pins to ECU input pins. Check for short to ground or battery voltage. Wiggle test harness for intermittent faults.
- Check sensor ground quality and measure resistance to chassis ground. Poor ground can cause incorrect readings.
- If wiring and connectors good but sensor output out-of-spec, remove and bench-test/replace the sensor. If bench testing not possible, replace with a known-good sensor.
- If new sensor and wiring OK but fault persists, inspect ECU inputs and grounds; consider ECU firmware update or module replacement only after excluding harness/sensor faults.
- Clear codes and perform relearn/calibration procedure if required by manufacturer. Retest by cycling ignition and road testing to verify the code does not return.
- Document repairs and verify related systems (brake lights, cruise control, ABS/regen) operate normally.
- Safety note: if vehicle is hybrid/EV, de-energize high-voltage system per service manual before working in the pedal area or near HV components.
Likely causes
- Damaged/contaminated connector at the brake pedal sensor or broken wire in harness
- One sensor producing out‑of‑range voltage (open, short to voltage/ground) while the other is normal
- Sensor mechanical misalignment so the expected signals aren’t produced simultaneously
- Faulty ground or 5V reference supply to sensors
Fault status
Status
Control module could not validate brake pedal position sensors A and B. Check sensors, wiring and module inputs for open/short/out‑of‑range signals.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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