Key Interlock System Circuit Troubleshooting

Disconnect steering lock assembly connector (6P).
Turn the ignition key to ACC (I) or ON (II).
Connect the No. 4 terminal of steering lock assembly connector (6P) to the battery positive terminal, and connect the No. 3 terminal to the battery negative terminal.

Fig 1: Connecting No. 4 Terminal Of Steering Lock Assembly Connector (6P) To Battery Positive Terminal
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check the key interlock solenoid operation. A clicking sound should be heard while the ignition key stays in ACC (I) and ON (II), and you should not be able to turn it to the OFF (0) 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.
Check for continuity between the No. 3 terminal of the steering lock assembly connector (6P) and body ground.

Fig 2: Checking Continuity Between No. 3 Terminal Of Steering Lock Assembly Connector (6P) & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Go to step 6.
2. NO - Repair open in the wire between the No. 3 terminal of the steering lock assembly connector (6P) and ground (G401), or repair poor ground (G401).
Turn the ignition switch ON (II), and measure the voltage between the No. 3 and No. 4 terminals of the steering lock assembly connector (6P).

Fig 3: Measuring Voltage Between No. 3 & No. 4 Terminals Of Steering Lock Assembly Connector
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 7.
2. NO - Check for open or short in the wire between the No. 4 terminal of steering lock assembly connector and the multiplex control unit. If the wire is OK, check for loose terminal fit in the multiplex control unit connectors. If necessary, substitute a known-good multiplex control unit and recheck.
Disconnect the park pin switch connector (4P).
Check for continuity between the No. 3 and No. 4 terminals of the park pin switch connector (4P) while you move the shift lever in and out of the P position.

Fig 4: Checking Continuity Between No. 3 & No. 4 Terminals Of Park Pin Switch Connector 4P
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there no continuity with the shift lever in the P position, and continuity with the shift lever in any position other than P?
1. YES - Repair open or short in the wires between the park pin switch connector and the multiplex control unit. If wires are OK, check for loose terminal fit in the multiplex control unit connectors. If necessary, substitute a known-good multiplex control unit and recheck.
2. NO - Inspect the park pin linkage. If the linkage is OK, replace the park pin switch.