Code
P1575
HUMMER
P — Powertrain
Extended Travel Brake Switch Circuit
AI status
Completed
Completed
100%
Causes
- Faulty or misadjusted brake pedal position / brake light switch
- Open, short, or high-resistance wiring in the brake switch circuit
- Poor connector contact, corrosion, or damaged pins at switch or module connector
- Blown fuse or poor ground related to the brake switch circuit
- Module input fault or intermittent BCM/ECM internal failure
- Foreign debris, damaged pedal assembly, or mechanical interference altering switch travel
Symptoms
- Brake lights may be inoperative, stuck on, or flicker
- Cruise control may not engage or may immediately cancel
- Shift interlock / gear shift may not release normally
- Illumination of MIL or brake-related warning lamps
- Possible erratic behavior of systems that use brake switch input (ABS, cruise, traction control)
What to check
- Read freeze frame / live data with a capable scan tool to confirm switch status and related inputs
- Perform visual inspection of brake switch, connector, and wiring for damage, corrosion, or detached connectors
- Check related fuses and ground points for continuity and tightness
- Backprobe the brake switch connector and observe voltage or signal while operating the pedal
- Wiggle test wiring while monitoring scan tool or multimeter for intermittent changes
Signal parameters
- Key ON / engine OFF: brake switch signal should change state when pedal is pressed and released
- Typical voltages (vehicle dependent): approx. 0–1 V when pulled to ground or 9–12 V when pulled to battery — confirm expected polarity for the vehicle
- Continuity across switch contacts when actuated (near 0 Ω) and open when released; open-circuit or very high resistance indicates failure
- Scan tool Boolean: brake switch status should toggle cleanly between 0/1 (OFF/ON) with pedal movement
Diagnostic algorithm
- Retrieve DTCs and related live data. Note current status of brake switch input and any accompanying codes.
- Visually inspect the brake switch, pedal travel, switch mounting, connector, and wiring harness for damage, contamination, or pin corrosion.
- Verify fuses and engine/BCM ground points related to the brake switch circuit.
- With ignition ON (engine off), backprobe the switch connector and operate the pedal while observing voltage and continuity. Compare to expected behavior for this vehicle (switch should change state cleanly).
- If signal is incorrect, disconnect switch and measure resistance across its terminals while actuating. Replace switch if it does not open/close reliably.
- If switch tests good, inspect wiring for opens/shorts: perform continuity checks from switch connector to the module connector and check for shorts to ground or battery.
- Repair/replace damaged wiring, connectors, or the switch as required. Apply dielectric grease to clean connectors before reassembly if corrosion was present.
- After repairs, clear codes, perform relearn procedures if required by manufacturer, and verify proper operation over several on/off cycles and a road test.
- If wiring and switch check good but code returns, test or replace the body control module / brake input module per manufacturer procedures.
Likely causes
- Brake switch out of adjustment or mechanically worn
- Corroded/loose connector at the brake switch
- Broken or chafed wire in harness near pedal or steering column
- Short to ground or short to battery power in the switch circuit
- Faulty body control module (less common)
Fault status
Status
Extended Travel Brake Switch Circuit — Brake switch input is out of expected range (open, short, intermittent, or abnormal travel).
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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