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Home / DTC / P1813 — Brake signal error

P1813 — Brake signal error

Detailed page for trouble code P1813.

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Code

P1813

MITSUBISHI P — Powertrain

Brake signal error

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty brake light/brake pedal switch
  • Broken, shorted or corroded wiring or connector in brake switch circuit
  • Blown fuse or faulty relay powering brake switch circuit
  • Poor ground at module or switch connector
  • Intermittent connection from wear or mechanical damage near pedal
  • Faulty body control module (BCM), ABS module or transmission control module reading the signal

Symptoms

  • Brake lights fail to illuminate or stay on
  • Cruise control disabled or will not set/release
  • Shift interlock/park release may not operate (car won’t shift out of Park)
  • ABS/traction control or other warning lights illuminated
  • Stored trouble codes related to brake switch or communications

What to check

  • Retrieve all stored and pending codes and freeze frame data with a scan tool
  • Visually inspect brake switch, wiring harness, and connectors at the pedal and at relevant modules for damage/corrosion
  • Confirm brake lights operate when pedal is depressed
  • Check relevant fuses and relays for continuity and proper operation
  • Monitor live data on a scan tool: verify brake pedal/switch status bit changes when pedal is pressed/released
  • Backprobe brake switch connector and measure voltage and continuity while operating pedal

Signal parameters

  • Typical switch behavior: open when pedal released, closed when depressed (or switched-to-ground type in some systems)
  • Expected voltage: ~12 V on feed; switch output typically 0 V (ground-switch) or ~12 V when pressed depending on vehicle design
  • Continuity when closed: 10 kohm (infinite)
  • Scan-tool data: brake switch status should toggle between 0 and 1 (or Off/On) immediately when pedal is moved

Diagnostic algorithm

  1. Connect scan tool, record P1813 and any related codes. Check live data for brake switch status.
  2. Perform visual inspection of brake pedal area, switch, wiring harness, and connectors. Repair visible damage.
  3. Verify brake lights function. If brake lights do not illuminate, check bulbs and fuses first.
  4. With ignition on, backprobe the brake switch connector: verify feed voltage (~12 V) and that switch changes output when pedal is pressed. Measure continuity across switch as pedal is depressed.
  5. If the switch reads incorrectly, adjust or replace the brake switch. After replacement, clear codes and re-test.
  6. If switch tests good, trace wiring between switch and BCM/ABS/TCU: check for opens/shorts, intermittent faults, and poor grounds. Repair wiring as needed.
  7. If wiring and switch are good but signal not seen at module, check connector pins at module for corrosion or bent pins and verify module ground.
  8. As a last step, consider module fault: verify communications with other modules and test/replace BCM/ABS/TCU only after eliminating harness and switch faults.
  9. After repairs, clear codes and perform function checks and test drive to confirm code does not return.

Likely causes

  • Brake switch misadjusted or failed
  • Open/short in harness between brake switch and BCM/ABS/TCU
  • Corroded/loose connector at switch or module
  • Blown fuse supplying brake switch circuit
  • Module fault after electrical troubleshooting

Fault status

⚠️ Status
Brake signal circuit abnormal — brake switch input missing or out of expected range. Possible open/short, bad connection, or control module fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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