2003 Acura MDX BaseFACTORY OEM SERVICE PROCEDURE

Brake Pedal Position Switch Signal Circuit Troubleshooting

NOTE: Before troubleshooting, check the No. 47 STOP (20 A) fuse in the under-hood fuse/relay box.
  1. Turn the ignition switch ON (II).
  2. Check the BRAKE SWITCH in the DATA LIST with the HDS.

    Does it indicate OFF? 

    1. YES  - Go to step 3.
    2. NO  - Inspect the brake pedal position switch (see BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ).
  3. Press the brake pedal, and check the BRAKE SWITCH in the DATA LIST with the HDS.

    Is it ON? 

    1. YES  - The brake pedal position switch signal circuit (BK SW line) is OK.
    2. NO  - Go to step 4.
  4. Release the brake pedal.
  5. Turn the cruise control main switch ON.
  6. Check the CRUISE BRK SW in the DATA LIST with the HDS.

    Does it indicate ON? 

    1. YES  - Go to step 7.
    2. NO  - Go to step  16.
  7. Press the brake pedal, and check the CRUISE BRK SW in the DATA LIST with the HDS.

    Is it OFF? 

    1. YES  - Go to step 8.
    2. NO  - Go to step  26.
  8. Inspect the brake pedal position switch (see BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ).

    Is it OK? 

    1. YES  - Go to step 9.
    2. NO  - Replace or adjust the brake pedal position switch (see BRAKE PEDAL AND BRAKE PEDAL POSITION SWITCH ADJUSTMENT ), and recheck.
  9. Turn the ignition switch OFF.
  10. Jump the SCS line with the HDS.
  11. Disconnect under-hood fuse/relay box 7P connector.
  12. Disconnect the taillight connectors.
  13. Disconnect PCM connector B (56P).
  14. Check for continuity between PCM connector terminal B39 and body ground with the brake pedal pressed.
    Fig 1: Checking Continuity Between PCM Connector Terminal B39 And Body Ground With Brake Pedal Pressed
    G03639904Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Repair short in the wire between the PCM (B39) and the under-hood fuse/relay box.
    2. NO  - Go to step 15.
  15. Check for continuity between PCM connector terminal B39 and under-hood fuse/relay box 7P connector terminal No. 5 with the brake pedal pressed.
    Fig 2: Checking Continuity Between PCM Connector Terminal B39 And Under-Hood Fuse/Relay Box 7P Connector Terminal No. 5
    G03639905Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Update the PCM if it does not have the latest software, or substitute a known-good PCM (see PCM UPDATING AND SUBSTITUTION FOR TESTING ), then recheck. If the symptom/ indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ).
    2. NO  - Repair open in the wire between the PCM (B39) and the under-hood fuse/relay box, and recheck.
  16. Test the cruise control main switch (see CRUISE CONTROL MAIN SWITCH TEST/ REPLACEMENT ).

    Is it OK? 

    1. YES  - Go to step 17.
    2. NO  - Replace the cruise control main switch (see CRUISE CONTROL MAIN SWITCH TEST/ REPLACEMENT ), and recheck.
  17. Turn the ignition switch OFF.
  18. Jump the SCS line with the HDS.
  19. Disconnect the cruise control main switch 8P connector.
  20. Disconnect PCM connector B (56P).
  21. Check for continuity between PCM connector terminal B38 and body ground.
    Fig 3: Checking Continuity Between PCM Connector Terminal B38 And Body Ground
    G03639906Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step  24.
    2. NO  - Go to step 22.
  22. Connect cruise control main switch 8P (5P*) connector terminal No. 4 (No. 2*) to body ground with a jumper wire.
    Fig 4: Connecting Cruise Control Main Switch 8P (5P*) Connector Terminal No. 4 (No. 2*) To Body Ground With Jumper Wire
    G03639907Courtesy of AMERICAN HONDA MOTOR CO., INC.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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