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Home › Infiniti › 2003 › M45 › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P1805: Brake Switch › Diagnostic Procedure

Diagnostic Procedure

  1. Turn ignition off. Check stop lamp operation. 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 Fig 1 . Measure voltage between ground and stop lamp switch harness connector terminal No. 1 (Red/Yellow wire). If battery voltage exists, go to step  4 . If battery voltage does not exist, go to next step.
  3. Check the following:
    • Check for poor connection at White, 4-pin in-line harness connector M401 terminal No. 1 (Red/Yellow wire). Connector M401 is located near stop lamp switch. See Figure .
    • Check Black, 20-pin joint connector No. 7 (connector M46) located behind center of instrument panel. See Figure and Figure .
    • Check for poor connection at fuse block No. 1 connector M1 terminal 3B (Blue/Black wire). See Figure .
    • Check fuse No. 17 (15-amp) located in fuse block No. 1.
    • Check for open or short between stop lamp switch and battery.

    Repair as necessary.

  4. Turn ignition off. Disconnect ECM harness connector. See Figure . Disconnect stop lamp switch harness connector. See Fig 1 . Check continuity of Red/White wire between stop lamp switch harness connector terminal No. 2 and ECM harness connector terminal No. 106. See Figure . Continuity should exist. Also, check circuit for short to ground and short to voltage. If problem is found, go to next step. If circuit is okay, go to step  6 .
  5. Check the following:
    • Check for poor connection at White, 4-pin in-line harness connector M401 terminal No. 2 (Red/White wire). Connector M401 is located near stop lamp switch. See Figure .
    • Check for poor connection at Super Multiple Junction harness connector F105 terminal 22T (Red/White wire). See Figure and Figure .
    • Check Black, 20-pin joint connector No. 7 (connector M46) located above stop lamp switch. See Figure and Figure .
    • Check for open or short between stop lamp switch and ECM.

    Repair as necessary.

  6. Check continuity between stop lamp switch terminals. With brake pedal depressed, continuity should exist. With brake pedal fully 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.
Fig 1: Locating Stop Lamp Switch
G00103721Courtesy of NISSAN MOTOR CO., U.S.A.
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