Code
C0047
FIAT
C — Chassis
Brake pedal sensor / brake switch
AI status
Completed
Completed
100%
Causes
- Faulty brake pedal position sensor or brake light switch
- Damaged or corroded connector or wiring (open, short to ground or to battery)
- Incorrect switch alignment or mechanically jammed pedal/switch
- Blown fuse or poor ground for the sensor circuit
- Intermittent module communication or module input fault
Symptoms
- Brake lights may not illuminate or remain on
- Cruise control may not engage or may disengage immediately
- ABS/traction control warning light or other related lamps illuminated
- Engine start/stop or keyless start function may be inhibited
- Shift-interlock (automatic) may not release
What to check
- Read stored codes and any related codes from ABS, BCM and engine ECU
- Check brake lights operation while pressing pedal
- Visually inspect switch, connector and wiring for damage or corrosion
- Backprobe switch connector and observe signal while operating pedal
- Check fuse(s) and ground(s) for the brake switch/circuit
Signal parameters
- Typical switch type: open at rest, closed when pedal pressed (or vice versa on some models)
- Typical switched voltage: 0 V (ground) or battery voltage (~12 V) when closed — some modules use a 5 V reference and return
- Brake pedal position sensor (potentiometer) output (if fitted): approximately 0.5–4.5 V across pedal travel
- Continuity: closed switch ≈
- Intermittent or noisy signal when harness is damaged (voltage jumps, spikes, or dropouts)
Diagnostic algorithm
- Retrieve all related codes from all control modules and record freeze-frame/conditions.
- Verify symptom: observe brake lights and read live data for brake switch/BPP signal with a scan tool while operating pedal.
- Visually inspect connector and wiring at the switch for corrosion, pin damage, or water ingress. Repair as needed.
- Backprobe the switch connector. With ignition on, measure reference, signal and ground. Verify expected voltages change when pedal is pressed.
- Check continuity of switch contacts with a multimeter (open vs closed state). For a potentiometer type, measure output voltage sweep across pedal travel.
- Wiggle test wires while monitoring signal to detect intermittent/open faults. Check continuity to the receiving module connector.
- Check related fuses and grounds. Repair any poor grounds or blown fuses.
- If wiring and connector are good but signal is out of range or inconsistent, replace the brake pedal switch/sensor.
- After repair, clear codes and perform a road/test bench check. If replacement is performed, follow any required calibration or programming procedure.
- If fault persists, inspect receiving module inputs and CAN/communication for faults and consider module diagnosis.
Likely causes
- Brake light switch contacts worn or stuck
- Plugged or corroded connector at switch (water ingress)
- Broken wire in harness between switch and ECU/ABS/BCM
- Switch physically mis-positioned after pedal/suspension work
- Aftermarket components or improper replacement switch
Fault status
Status
Brake pedal sensor / brake switch circuit fault detected. The control unit has seen an invalid, missing or intermittent brake pedal input. Related safety and convenience functions (ABS, traction control, cruise control, shift interlock, start/stop) may be affected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Repair manuals
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26
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