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DTC codes / Jaguar codes / P1571

P1571 · JaguarBrake Switch

P1571 on a Jaguar indicates that the brake switch circuit has reported an implausible or missing signal to the engine control module (ECM) or body control module (BCM). The computer expects a specific voltage transition when the brake pedal is pressed or released, and it has detected a fault in that expected signal, often due to a faulty switch, wiring issue, or misadjusted pedal linkage.

SystemPowertrain
Code typeJaguar specific
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Brake lights may fail to illuminate when the pedal is pressed, or may stay on continuously.
  • The cruise control may not disengage when the brake pedal is pressed, or may not engage at all.
  • The transmission may be difficult to shift out of Park, or the shift interlock may not release.
  • A warning light (check engine or brake system) may be illuminated on the dashboard.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.
  • Electronic stability control (ESC) or traction control warning may appear if the brake signal is used by those systems.

Common causes, most likely first

  1. Faulty brake pedal switch (also called brake light switch) – most common cause.
  2. Misadjusted or loose brake switch mounting, causing incorrect plunger contact.
  3. Worn or damaged wiring harness at the brake switch connector, often due to pedal movement.
  4. Corroded or loose electrical connector pins at the switch or module.
  5. Blown fuse or faulty relay in the brake light circuit (though less common for this specific code).
  6. Faulty body control module (BCM) or engine control module (ECM) – rare but possible.
  7. Aftermarket accessories (e.g., trailer wiring) tapping into the brake circuit and causing signal interference.

How to diagnose and fix it

  1. Verify the brake lights operate correctly with a helper, checking for consistent on/off operation.
  2. Inspect the brake switch connector and wiring for damage, corrosion, or loose pins; repair as needed.
  3. Check the brake switch adjustment: ensure the plunger fully extends and retracts with pedal movement, and adjust per Jaguar service procedure.
  4. Test the brake switch electrically with a multimeter for continuity and voltage signals in both pedal positions; replace if faulty.
  5. Clear the code and test-drive to see if it returns; if it does, perform a wiggle test on the harness while monitoring live data for the brake switch signal.
  6. If the switch and wiring are good, check for technical service bulletins (TSBs) or software updates for the BCM/ECM that may address false brake switch codes.
  7. As a last resort, diagnose the BCM/ECM for internal faults, but only after eliminating all external circuit issues.

Brake Switch Code Misdiagnosis Traps

  • A brake switch that tests fine with a multimeter can still set P1571 intermittently due to internal contact wear that only shows under load or temperature changes.
  • The brake switch on many Jaguars has two separate internal circuits (one for brake lights, one for the ECM/BCM); one can fail while the other still works, so always test both outputs.
  • After replacing the brake switch, the pedal position sensor or switch adaptation may need to be reset with a factory-level scan tool, or the code may persist.
  • A dragging brake pedal or worn pedal bushing can prevent the switch from fully actuating, mimicking a faulty switch.
  • P1571 can be set by a low battery or voltage spikes; always check battery health and charging system before condemning the switch.

Can I keep driving with P1571?

If the brake lights are working normally and the pedal feels fine, you can drive cautiously to a repair shop, but avoid relying on cruise control and be aware that the transmission may not shift out of Park easily. If the brake lights are inoperative or stay on continuously, do not drive, as this is a safety hazard.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Jaguar vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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