Multiplex Control System Troubleshooting
TroubleshootingSpecial Tool Required
MPCS service connector 07WAZ-001010A
Mode 1
Description:
Mode 1 is a communication line and CPU self test. If a problem occurs on a communication wire or with an individual control unit, multiplex system will store a DTC as long as the fault is still present.
To Enter Mode 1:
1. Check the No.9 (10 A) fuse in the driver's u-dash fuse/relay box and the No.13 (7.5 A) fuse in the Passenger's under-dash fuse/relay box.
Are the fuses OK?
YES - Go to step 2.
NO - Find and repair the cause of the blown fuse.
2. Connect the special tool to the multiplex control system (MPCS) inspection connector (A).
3. Turn the ignition switch ON (II). If the driver's seat belt is unbuckled, the seat belt reminder will beep five times.
4. 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 second, then blink and deep for 0.2 second. This indicated that the system is in mode 1.
Did the multiplex system enter mode 1?
YES Go to step 5.
NO - Go to step 6.
DTC 1 - 6:
5. Check for a DTC.
- If there is no DTCs present:
The ignition key light and beeper will not blink/deep again after the mode 1 indication.
- If there is no DTC present:
About 1 second after entering mode 1, the ignition key light and beeper indicate the DTC(s), then repeat it every 3 seconds. If there is more than one DTC, the system will indicate them in ascending order.
Is there a DTC present?
YES - Follow the procedure in the Chart given.
NO - Go to Mode 2.
6. Remove the special tool from the MPCS inspection connector.
7. Remove driver's multiplex control unit from the driver's under-dash fuse/relay
8. Check for voltage between the No.12 terminal of the driver's fuse/relay box socket and body ground.
Is there battery voltage?
YES - Go to step 9.
NO - Replace the driver's under-dash fuse/relay box.
9. Turn ignition switch ON (II)
10. Check for voltage between No.24 terminal of the driver's fuse/relay socket and body ground.
Is there battery voltage?
YES - Go to step 11.
NO - Repair an open in the wire between No.13 fuse in the passenger's under-dash fuse/relay box and the driver's under-dash fuse/relay box socket.
11. Check for continuity between No.14 terminal of the driver's under-dash fuse/relay box socket and body ground.
Is there continuity?
YES - Go to step 12.
NO - Repair an open in the wire between driver's multiplex and body ground. If the wire is OK, check for poor ground at G401.
12. Check for continuity between No.11 terminal of the driver's multiplex control unit connector B (22P) and body ground.
Is there continuity?
YES - Go to step 13.
NO - Repair an open in the wire between driver's multiplex control unit connector B and ground. If the wire is OK, check for door ground atG501.
13. Check for continuity between No.1 terminal of the MPCS inspection connector and the No.15 terminal of the driver's under-dash fuse/relay box socket.
Is there continuity?
YES - Go to step 14.
NO - Repair an open in the wire between the MPCS inspection connector and the driver's under-dash fuse/relay box. If the wire is OK, replace the driver' s under-dash fuse/relay box.
14. Check for continuity between No.3 terminal of the MPCS inspection connector and body ground.
Is there continuity?
YES - If there us still no mode 1 indication, replace the driver's multiplex control unit and recheck the symptom.
NO - Repair an open in the wire between the inspection connector and body ground. If the wire is OK, check for a poor ground at G401.
Mode 2
Description:
Mode 2 is an easy way to identify a problem circuit without having to test circuit with a DVOM Mode 2 will confirm a switch/circuit is working by flashing the ignition key light and sounding the beeper as the circuit is used. The multiplex control system will confirm inputs as they are grounded except for the following circuits.
- Turning the intermittent wiper ring (several confirmations as ring is turned).
- Turning the dash light illumination dimmer (several confirmations as the knob is turned).
- The Audio unit. Navigation display, RES display, DVD player (confirmation as any one component is disconnected).
To Enter Mode 2:
1. From mode 1, disconnect the special tool from the multiplex control system (MPCS) inspection connector for between 5 and 10 seconds, then reconnect it The ignition key light should come on and the beeper should beep for 2 seconds, then blink/beep twice more at 0.2 second intervals This indicates the system has entered mode 2.
2. Operate the switch as described in the charts given.
NOTE: Key cylinder switch tests require a second key be used to perform.
Did the multiplex control system confirm all the circuits by flashing the ignition key light and sounding the beeper?
YES - The multiplex system is OK If the symptom is still present, go to the input test for the system with the problem, or refer to multiplex input test.
- Power door locks.
- Security (EX models).
- Keyless (EX models).
- Power windows (includes key-off timer operation).
- Entry light control, Key light timer.
- Windshield wiper controls (front and rear).
- Automatic lights off (EX models).
- Reminder chimes (Key in seat belt lights on).
- Dash lights brightness control.
- Engine oil pressure indicator.
NO - Find the open or short in the circuit that was not confirmed by the multiplex control system If the circuit is OK, replace the multiplex control unit that monitors the circuit.