2003 Acura MDX BaseFACTORY OEM SERVICE PROCEDURE

Key Interlock System Circuit Troubleshooting

  1. Disconnect the key switch connector (7P) from the steering lock assembly.
  2. Connect the No. 7 terminal of the key switch connector to the battery positive terminal, and connect the No. 5 terminal to the battery negative terminal.
    Fig 1: Connecting No. 7 Terminal Of Key Switch Connector To Battery Positive Terminal And No. 5 Terminal To Battery Negative Terminal
    G03640538Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. Turn the ignition switch to ACC (I), then push the ignition key.
  4. Check the key interlock solenoid operation. A clicking sound should be heard while pushing the ignition key, and you should not be able to turn it to the OFF position.

    Does the key interlock solenoid operate properly? 

    1. YES  - Go to step 5.
    2. NO  - Faulty key interlock solenoid/switch. Replace the ignition key cylinder/steering lock assembly.
  5. Measure the voltage between the No. 7 terminal and body ground.
    Fig 2: Measuring Voltage Between No. 7 Terminal And Body Ground
    G03640539Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES  - Go to step 6.
    2. NO  - Check for a blown No. 47 (20 A) fuse in the underhood fuse/relay box. If the fuse is OK, repair open or short in the wire between the No. 7 terminal of the key switch connector and underhood fuse/relay box.
  6. Disconnect the switch assembly connector (6P) on the shift lever.
  7. With the shift lever in Park and pushed to the right, check for continuity between the No. 4 and No. 2 terminals of the switch assembly connector (6P).
    Fig 3: Checking For Continuity Between No. 4 And No. 2 Terminals Of Switch Assembly Connector (6P)
    G03640540Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step 8.
    2. NO  - Repair open in the wires between the park pin switch and the switch assembly connector (6P). If the wires are OK, remove the shift lever assembly (see SHIFT LEVER REMOVAL  ), and replace the shift lever detent bracket assembly (see SHIFT LEVER DISASSEMBLY/REASSEMBLY  ).
  8. Check for continuity between the No. 4 terminal of the switch assembly connector (6P) and the No. 5 terminal of the key switch connector.
    Fig 4: Checking For Continuity Between No. 4 Terminal Of Switch Assembly Connector (6P)
    G03640541Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step 9.
    2. NO  - Repair open in the wire between No. 4 terminal of the switch assembly connector (6P) and the No. 5 terminal of the key switch connector.
  9. Check for continuity between the No. 2 terminal of the switch assembly connector (6P) and body ground.
    Fig 5: Checking For Continuity Between No. 2 Terminal Of Switch Assembly Connector (6P) And Body Ground
    G03640542Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Check for loose terminal pin fit in the key switch connector and switch assembly connector (6P). If necessary, substitute a known-good steering lock assembly.
    2. NO  - Repair open in the wire between the No. 2 terminal of the switch assembly connector (6P) and ground (G401), or repair poor ground (G401).
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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.