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Home › Infiniti › 2003 › I35 › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P1805: Brake Switch › Diagnostic Procedure

Diagnostic Procedure

  1. Check stop lamp operation while depressing and releasing brake pedal. If stop lamps operate properly, go to step  4 . If stop lamps do not operate properly, go to next step.
  2. Disconnect stop lamp switch harness connector. See Figure . Measure voltage between ground and stop lamp switch harness connector terminal No. 1 (Orange wire). If battery voltage exists, go to step  4 . If battery voltage does not exist, go to next step.
  3. Check the following:
    • Check fuse No. 20 (15-amp) located in fuse block under left side of instrument panel.
    • Check for poor connection at fuse block connector M17 terminal 11K (Orange wire). See Figure .
    • Check for poor connection at Super Multiple Junction (SMJ) connector M15 terminal 4A (Orange wire). See Figure . SMJ connector M15 is located under left side of instrument panel. See Figure .
    • Check for open or short between stop lamp switch and fuse.
    Repair as necessary.
  4. Disconnect ECM harness connector. Check continuity of Red/Green wire between stop lamp switch harness connector terminal No. 2 and ECM harness connector terminal No. 55. Also, check circuit for short to ground and short to voltage. If problem is found, go to next step. If problem is not found, go to step  6 .
  5. Check the following:
    • Check for poor connection at White, 18-pin connector F53 terminal No. 1 (Red/Green wire). See Figure . Connector is located near ECM. See Figure .
    • Check for poor connection at Super Multiple Junction (SMJ) connector M15 terminal 2A (Red/Green wire). See Figure . SMJ connector M15 is located under left side of instrument panel. See Figure .
    • Check for open or short between stop lamp switch and ECM.
    Repair as necessary.
  6. Check continuity between stop lamp switch terminals. When brake pedal is depressed, continuity should exist. When brake pedal is released, continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace stop lamp switch.
  7. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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