Multiplex Control System Troubleshooting
Special Tool Required:MPCS Service Connector 07WAZ-001010A
1. Check the No.9 and 13 passenger fuses.
Are the fuses OK?
YES-Go to step 2.
NO-Find and repair the cause of the blown fuse.
2. Test power and ground inputs to all three multiplex control units.
3. Check self-diagnosis function Mode 1 for a diagnostic trouble code (DTC) by connecting the special tool to the multiplex control inspection connector (A). After about 5 seconds, the ignition key light should come on and the beeper should beep for 2 seconds, then go off for 0.2 seconds, then blink and beep for 0.2 seconds. This means that you are in Mode 1 of the self-diagnosis function.
4. Turn the ignition switch ON (II).
Does the ignition key light blink and the beeper beep?
YES-There is a DTC. Count the blinks/beeps, then go to step 7.
NO-See if the SCS circuit is working properly. Go to step 5.
5. Check for continuity between the No.3 terminal of the inspection connector and the A15 terminal in the driver's unit.
Is there continuity?
YES-Go to step 6.
NO-Repair the open in the wire, and recheck for DTCs.
6. Check for continuity between the No.1 terminal of the inspection connector and body ground.
Is there continuity?
YES-Go to step 13.
NO-Repair the open in the wire, and recheck for DTCs.
7. One second after you go into self-diagnosis mode 1, the ignition key light and beeper indicate the DTC, and repeat it every 3 seconds. If there is more than one DTC, the system will indicate them in ascending order, beginning from the DTC with the lowest numerical value. Find your DTC in this table, then go to step 8 and check the communication lines.
8. With the ignition switch OFF, check for continuity according to the table.
Is there continuity?
YES-Go to step 9.
NO-Check for an open in the wire.
9. Turn the ignition switch ON (II), and check for voltage between the communication line and ground.
Does the voltage match the table?
YES-Communication lines are OK. Go to step 10.
NO- Repair the line according to the following.
- If the voltage is too high:
- Check for a short to another wire.
- Check for poor contact in the connector at the receiving unit.
- If the voltage is too low:
- Check for a short to ground or to another wire.
- Check for poor contact at the connector on the transmitting unit.
- Faulty circuit in the transmitting unit.
10. Shift to the sleep mode:
- Turn the ignition switch OFF.
- Cancel the key-off operation timer in the power window system by opening and closing one of the doors.
- Make sure that the exterior lights are off. If you do not operate any switches related to the multiplex control units within one minute after meeting the above conditions, the system function shifts to the sleep mode. (All of the switches must be turned OFF except door lock knob switches).
11. Confirm the sleep mode:
- Check for voltage in the BRN and PNK lines between control units. These should be approximately 12 volts in the sleep mode.
- Check for voltage between each communication line and body ground while shifting to the sleep mode. There should be no voltage.
- Check the parasitic draw at the battery while shifting to the sleep mode. Amperage should change from about 70 through 80 mA to less than 10 mA.
12. Confirm the wake up mode.
- When the ignition switch in turns ON (II), all of the multiplex control units wake up at the same time without "talking" to each other through the communication lines.
- When any switch in the multiplex system is turned on, it wakes up its related control unit which, in turn, wakes up the other units.
After confirming the sleep mode, look in the following tables for the switch most closely related to the problem. Operate that switch and see if its control unit wakes up.
NOTE: If any control unit is faulty and will not wake up, several pants of the system will malfunction at the same time.
In each table, the control unit is followed by a list of the switches and input signals that can wake it up.
Is the wake-up function OK?
YES-Troubleshoot the individual system function that had a problem.
NO-Repair the open or short in the communication line(s).
13. From Mode 1, disconnect the special tool from the multiplex control inspection connector for about ten seconds, then reconnect it. The ignition key light should come on and the beeper should beep for 2 seconds, then blink and beep twice more at 0.2 second intervals. This means the system has gone from Mode 1 to Mode 2.
Mode 2:
NOTE: To cancel mode 2, disconnect the SCS service connector from the multiplex control inspection connector for more than 10 seconds or turn the ignition switch OFF.
14. Look in the following tables for the switch most closely related to the problem. While still in Mode 2, operate that switch to test the circuit between the switch and its control unit. If the circuit is OK, the ignition key light should blink once and the beeper should beep once. If the circuit is faulty, there will be no indication.
Does the ignition key light blink and beeper beep?
YES-The circuit is OK. Refer to the test(s) for that individual system.
NO-Go to step 15.
In each table, the control unit is followed by a list of circuits that it can check in Mode 2.
15. Check two or three more circuits listed for that control unit.
Does the ignition key light blink and the beeper beep for each circuit?
YES-The additional circuits are OK. Repair the short or open in the circuit that failed the test in the preceding step.
NO-Multiple failed circuits can mean that the control unit has failed, but without triggering a DTC. Test a few more circuits. If they also fail, substitute a known-good control unit, then recheck. If the system works properly, the original control unit is faulty; replace it. If there is a still a malfunction, substitute a known-good control unit for the next most likely faulty control unit, then recheck. If the system works properly, that control unit is faulty; replace it.