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Home >> Mitsubishi >> 2004 >> Montero XLS >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Hydraulic Brake Booster >> Diagnostic Tests >> DTC 54: Motor Relay (Open Circuit, Short Circuit Or Failure Of Motor Relay Coil) >> Diagnosis & Repair

Diagnosis & Repair

NOTE: For component location and connector identification, see Figure and Figure .
  1. Erase DTC memory. Check for DTCs. If DTC 55 is not set, go to next step. If DTC 55 is set, perform diagnosis and repair for DTC 55. See DTC 55: PUMP MOTOR CIRCUIT (PUMP MOTOR ENERGIZED ABNORMALLY FOR LONG PERIOD)  . Go to step  25 .
  2. With ignition off, depress brake pedal repeatedly more than 40 times until pedal depressing force feels heavy. Turn ignition on. Listen for pump motor operation. If pump motor operates, go to step  22 . If pump motor does not operate, go to next step.
    3. CAUTION: Connect battery terminals as illustrated. Reversing polarity will damage internal diode.
    Fig 1: Testing Motor Relay "A"
    G00313689Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  3. Check motor relay "A" as illustrated. See Fig 1 . If relay is okay, go to next step. If relay is not okay, replace relay, then go to step  25 .
    4. CAUTION: Connect battery terminals as illustrated. Reversing polarity will damage internal diode.
    Fig 2: Testing Motor Relay "B"
    G00313690Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  4. Check motor relay "B" as illustrated. See Fig 2 . If relay is okay, go to next step. If relay is not okay, replace relay, then go to step  25 .
  5. Inspect the following connectors for loose, corroded or damaged terminals, or terminals pushed back in the connector:
    • Motor relay "A" connector B-53X.
    • Motor relay "B" connector B-54X.
    • HBB connectors B-17 and B-18.

    If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to next step.

  6. Remove motor relay "A". Measure voltage between ground and terminal No. 5. Battery voltage should exist. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  10 .
  7. Turn ignition on. Measure voltage between ground and motor relay "A" harness connector terminal No. 3. Battery voltage should exist. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  11 .
  8. Remove motor relay "B". Measure voltage between ground and terminal No. 4. Battery voltage should exist. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  12 .
  9. Turn ignition on. Measure voltage between ground and motor relay "B" harness connector terminal No. 3. Battery voltage should exist. If battery voltage exists, go to step  14 . If battery voltage does not exist, go to step  13 .
  10. Check wire between fusible link No. 32 and motor relay "A" connector B-53X terminal No. 5. See Fig 3 . If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
    Fig 3: Locating Fusible Link No. 32
    G00313691Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  11. Check wire between motor relay "A" connector B-53X terminal No. 3 and junction block connector D-208 terminal No. 4. Also, check connectors D-116, D-212 and E-111 for loose, corroded or damaged terminals, or terminals pushed back in the connector. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
  12. Check wire between fusible link No. 32 and motor relay "B" connector B-54X terminal No. 4. See Fig 3 . If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
  13. Check wire between motor relay "B" connector B-54X terminal No. 3 and multipurpose fuse No. 17. Also, check intermediate connector E-111 for loose, corroded or damaged terminals, or terminals pushed back in the connector. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
  14. Check wire between HBB connector B-18 terminal No. 31 and motor relay "A" connector B-53X terminal No. 4. Also, check wire between HBB connector B-17 terminal No. 2 and motor relay "B" connector B-54X terminal No. 5. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
  15. Check M-ASTC-ECU connectors E-119 and E-120 for loose, corroded or damaged terminals, or terminals pushed back in the connector. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to next step.
  16. Disconnect M-ASTC-ECU connector E-120. Turn ignition on. Measure voltage between ground and connector E-120 terminal No. 48. Battery voltage should exist. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  18 .
  17. Disconnect M-ASTC-ECU connector E-119. Turn ignition on. Measure voltage between ground and connector E-119 terminal No. 24. Battery voltage should exist. If battery voltage exists, go to step  20 . If battery voltage does not exist, go to step  19 .
  18. Check wire between M-ASTC-ECU connector E-120 terminal No. 48 and motor relay "A" connector B-53X terminal No. 1. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
  19. Check wire between M-ASTC-ECU connector E-119 terminal No. 24 and motor relay "B" connector B-54X terminal No. 1. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to step  25 .
  20. With HBB connectors B-17 and B-18 disconnected, measure resistance between HBB terminals as specified in illustration. See Figure . If resistance is as specified in illustration, go to step  22 . If resistance is not as specified in illustration, go to next step.
  21. Remove HBB. See HYDRAULIC BRAKE BOOSTER  under REMOVAL & INSTALLATION. Remove pump motor and lead wire from HBB. See HYDRAULIC BRAKE BOOSTER  under OVERHAUL. Check that pump motor operates when battery voltage is applied. Also, check continuity of lead wire. If problem is found, replace pump motor or lead wire as necessary, then go to step  25 . If pump motor and lead wire are in good condition, replace master cylinder and hydraulic unit assembly, then go to step  25 .
  22. Inspect the following connectors for loose, corroded or damaged terminals, or terminals pushed back in the connector:
    • HBB connector B-17.
    • M-ASTC-ECU connector E-119.

    If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to next step.

  23. Check wire between M-ASTC-ECU connector E-119 terminal No. 25 and HBB connector B-17 terminal No. 4. If problem is found, repair as necessary, then go to step  25 . If problem is not found, go to next step.
  24. Clear DTC memory. Recheck for DTC. If DTC 54 is set, replace M-ASTC-ECU, then go to next step. If DTC 54 is not set, it can be assumed that this malfunction is intermittent.
  25. Clear DTC memory. Recheck for DTC. If DTC 54 is set, go to step  1 . If DTC 54 is not set, repair is complete.
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