Multiplex Control System (Hatchback): Other Honda Civic VII рестайлинг

Multiplex Communication

To reduce the number of wire harnesses, digital signals are sent via shared multiplex communication lines rather than sending normal electrical signals through individual wires.

1. The input signals from each switch are converted to digital signals at the central processing unit (CPU).
2. The digital signals are sent from the transmitting unit to the receiving unit as serial signals.
3. The transmitted signal is converted to a switch signal at the receiving unit, and it operates the related component or monitors a switch.
4. There are exclusive communication lines between the ECM, the gauge assembly, keyless receiver unit, and the under-dash fuse/relay box.

Wake-up and Sleep

The multiplex control system has "wake-up" and "sleep" functions to decrease parasitic draw on the battery when the ignition switch is OFF.

1. In the sleep mode, the multiplex control unit stops functioning (communication and CPU control) when it is not necessary for the system to operate.
2. As soon as any operation is requested (for example, a door is unlocked), the related control unit in the sleep mode immediately wakes up and begins to function.
3. When the ignition switch is turned OFF, and the driver's or front passenger's door is opened, then closed, there is about a 10 second delay before the control unit goes from the wake-up mode to the sleep mode.
4. If any door is open, the sleep mode will not function.
5. If a key is in the ignition switch, the sleep mode will not function.
6. When in sleep mode, the draw is reduced from 70 - 80 mA to less than 10 mA.

Fail-safe

To prevent improper operation, the multiplex control system has a fail-safe function. In the fail-safe mode, the output signal is fixed when any part of the system malfunctions (for example a faulty control unit or communication line).

Each control unit has a hardware fail-safe function that fixes the output signal when there is any CPU malfunction, and a software fail-safe function that ignores the signal from the malfunctioning control unit and allows the system to operate normally.

Scheme 4

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Scheme 7

1. Remove the driver's dashboard lower cover (see «DRIVER'S DASHBOARD LOWER COVER REMOVAL/INSTALLATION»(ref-171681-S12708113692005021000000) ).
2. Check the No. 9 (10A) fuse in the under-hood fuse/relay box and the No. 10 (7.5A) fuse in the under-dash fuse/relay box. Are the fuses OK? YES: Go to step 3. NO: Find and repair the cause of the blown fuse.
3. Turn the ignition switch ON (II). If the driver's seat belt is unbuckled the seat belt reminder will chime 6 times.
4. Set the ceiling light to the center position and close all the doors.
5. Connect the special tool (A) to the multiplex inspection connector (B).
6. After about 5 seconds the spotlight and ceiling light should come on for 2 seconds, go out, then blink on for 0.2 second to show the system is now in mode 1. Did the spotlight and ceiling light indicate mode 1? YES: Go to step 8 . NO: Go to step 7.
7. Check for continuity between terminal 4 of the under-dash fuse/relay box connector J and body ground. Is there continuity? YES: Replace the under-dash fuse/relay box. NO: Repair the open in the wire.If the wire is OK, repair G301.
8. If the DTCs are present, the spotlight and ceiling light will blink to indicate the DTC(s). If more than one DTC is present, the DTCs will be displayed in ascending order. If there are no DTCs the spotlight and ceiling light will not blink again after the Mode 1 indication. Are there any DTCs? YES: Go to step 9. NO: Go to the Mode 2 test.
9. Troubleshoot the DTC(s) in the order indicated using the following charts. If a faulty control unit is suspected, substitute it with a known food part and recheck for DTCs, If the DTC(s) is still present, go to the next step listed for the DTC. If the DTC(s) is no longer present replace the original part. Before replacing a Faulty ECM/PCM make sure it has the latest software revision. Update if necessary before swapping or replacing.

Scheme 8

1. From Mode 1, disconnect the special tool from the multiplex inspection connector for 5 to 10 seconds, and then reconnect it.
2. The spotlight and ceiling light should come on for 2 seconds, go out, then blink twice, 0.2 seconds each time. The system is now in Mode 2.
3. Operate the switches listed below: If the circuit is OK, the spotlight and ceiling light will blink once. If the circuit is faulty, the lights will not blink. Tip: Operate the switches most closely related to the problem you are diagnosing is a quick way of testing the circuits integrity.
4. If all inputs were confirmed, or multiple circuits failed at the same time in Mode 2, go to the multiplex sleep mode test. If a single switch fails in Mode 2, troubleshoot its circuit.

Scheme 9

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1. Remove the driver's dashboard lower cover (see «DRIVER'S DASHBOARD LOWER COVER REMOVAL/INSTALLATION»(ref-171681-S12708113692005021000000) ).
2. Disconnect the under-dash fuse/relay box connectors C, E, F, J, K, O, P, Q, X and Y. NOTE: All connectors are wire side of female terminals.
3. Inspect the connector and socket terminals to be sure they are all making good contact. If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system. If the terminals look OK, go to step 4.
4. Reconnect the connectors to the under-dash fuse/relay box, turn the ignition switch ON (II) to keep the system awake and make sure these input tests at the appropriate connectors on the under-dash fuse/relay box. If any test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, the multiplex control unit must be faulty. Replace the under-dash fuse/relay box assembly.

Scheme 12