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Home › Infiniti › 2003 › G35 4D Sedan, Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P1572: Automatic Speed Control Device Brake Switch › Diagnostic Procedure

Diagnostic Procedure

CAUTION: DO NOT use ECM ground terminals when measuring voltage. Damage to ECM transistor may result. Use engine ground.

For component location, see COMPONENT LOCATIONS  . For connector terminal identification, see CONNECTOR IDENTIFICATION  . For circuit diagram, see Fig 1 . For ECM pin voltage reference values, see Fig 2 .

  1. If using CONSULT-II, go to next step. If using generic scan tool, go to step  4 .
  2. Turn ignition on. Select BRAKE SW1 in DATA MONITOR mode with CONSULT-II. Check BRAKE SW1 indication under the following conditions:
    • When brake pedal is depressed, indication should be OFF.
    • When brake pedal is fully released, indication should be ON.

    If indication is as specified, go to next step. If indication is not as specified, go to step  6 .

  3. Turn ignition on. Select BRAKE SW2 in DATA MONITOR mode with CONSULT-II. Check BRAKE SW2 indication under the following conditions:
    • When brake pedal is fully released, indication should be OFF.
    • When brake pedal is depressed, indication should be ON.

    If indication is not as specified, go to step  11 . If indication is as specified, go to step  16 .

  4. Turn ignition on. Measure voltage between engine ground and ECM harness connector F101 terminal No. 59 under following conditions:
    • When brake pedal is depressed, voltage reading should be about zero volts.
    • When brake pedal is fully released, voltage reading should be battery voltage.

    If voltage reading is as specified, go to next step. If voltage reading is not as specified, go to step  6 .

  5. Turn ignition on. Measure voltage between ground and ECM harness connector F101 terminal No. 55 under following conditions:
    • When brake pedal is released, voltage reading should be about zero volts.
    • When brake pedal is fully depressed, voltage reading should be battery voltage.

    If voltage reading is not as specified, go to step  11 . If voltage reading is as specified, go to step  16 .

  6. Turn ignition off. Disconnect ASCD brake switch harness connector E111. Turn ignition on. Measure voltage between engine ground and ASCD brake switch harness connector E111 terminal No. 1. Battery voltage should exist. If battery voltage does not exist, go to next step. If battery voltage exists, go to step  8 .
  7. Check the following:
    • Fuse block (J/B) connector E101.
    • Fuse block (J/B) fuse No. 12 (10-amp).
    • Joint connector-2.
    • Harness for open or short between ASCD brake switch harness connector E111 and fuse block (J/B) fuse No. 12 (10-amp).
    Repair as necessary.
  8. Turn ignition off. Disconnect ECM harness connector F101. Check harness continuity between ECM harness connector F101 terminal No. 59 and ASCD brake switch harness connector E111 terminal No. 2. Continuity should exist. Also check harness for short to ground or short to power. If problem is found, go to next step. If no problem is found, go to step  10 .
  9. Check the following:
    • Harness connectors E108 and M15.
    • Harness connectors F102 and M72.
    • Harness for open or short between ECM harness connector F101 and ASCD brake switch harness connector E111.
    Repair as necessary.
  10. Turn ignition off. Disconnect ASCD brake switch harness connector E111. Check for continuity between ASCD brake switch harness connector E111 terminals No. 1 and 2 under the following conditions:
    • When brake pedal is depressed, continuity should not exist.
    • When brake pedal is fully released, continuity should exist.

    If continuity is as specified, go to step  16 . If continuity is not as specified, adjust ASCD brake switch and check for continuity again. If ASCD brake switch is faulty, replace ASCD brake switch.

  11. Turn ignition off. Disconnect stop lamp switch harness connector E112 (2-pin) or E124 (4-pin). Measure voltage between engine ground and stop lamp switch harness connector E112/E124 terminal No. 1. Battery voltage should exist. If battery voltage does not exist, go to next step. If battery voltage exists, go to step  13 .
  12. Check the following:
    • Fuse block (J/B) connector E101.
    • Fuse block (J/B) fuse No. 20 (10-amp).
    • Joint connector-2.
    • Harness for open or short between stop lamp switch and fuse block (J/B) fuse No. 20 (10-amp).
    Repair as necessary.
  13. Disconnect ECM harness connector F101. Check harness continuity between ECM harness connector F101 terminal No. 55 and stop lamp switch harness connector E112/E124 terminal No. 2. Continuity should exist. Also check harness for short to ground and short to power. If problem is found, go to next step. If no problem is found, go to step  15 .
  14. Check the following:
    • Harness connectors E108 and M15.
    • Harness connectors F102 and M72.
    • Joint connector-2.
    • Harness for open or short between ECM and stop lamp switch.
    Repair as necessary.
  15. Turn ignition off. Disconnect stop lamp switch harness connector E112/E124. Check for continuity between stop lamp switch harness connector E112/E124 terminals No. 1 and 2 under the following conditions:
    • When brake pedal is fully released, continuity should not exist.
    • When brake pedal is depressed, continuity should exist.
    If continuity is as specified, go to next step. If continuity is not as specified, adjust stop lamp switch and repeat this step. If stop lamp switch is faulty, replace stop lamp switch.
  16. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
Fig 1: DTC P1572 Circuit Diagram
G00275882Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: DTC P1572 ECM Pin Voltage Reference Values
G00275883Courtesy of NISSAN MOTOR CO., U.S.A.
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