Multiplex Control System: Overview Honda Odyssey II

Scheme 1

Scheme 2

System Descriptions

The multiplex control system has four internal functions

1. Multiplexing (send multiple signals over shared wires)
2. Wake up/sleep modes (runs at full power only on demand to reduce battery draw)
3. Fail-safe (fixes or ignores faulty signals)
4. Self-diagnosis (Mode 1 for the system, Mode 2 for input lines)

The system controls the function of the following circuits

1. Engine Oil Pressure Indicator
2. Seat Belt Reminder
3. Lights-on Reminder
4. Key-in Reminder
5. Key Light Timer
6. Dash Lights Brightness Control
7. Entry Light Control (EX and EXL models)
8. Automatic Lights-off (EX and EXL models)
9. Power Window (including key-off timer operation)
10. Wiper/Washers (including speed sensitive intermittent wiper)
11. Keyless/Power Door Locks
12. Interlock
13. Factory Security Alarm System ('01-04 EX and '02-04 EXL models)

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.

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

1. Check the No. 9 (10A) fuse in the driver's under-dash fuse/relay box and the No. 13 (7.5A) 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 .
5. Check for a DTC. If there is no DTCs present: The ignition key light and beeper will not blink/beep again after the Mode 1 indication. If there are DTC(s) 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 below. NO: Go to Mode 2 (see «Mode 2»(ref-171523-S07979991762005020700000) ).
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 box.
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 box 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 control unit 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 at G501.
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 is 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 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

1. Turning the intermittent wiper ring (several confirmations as ring is turned)
2. Turning the dash light illumination dimmer (several confirmations as the knob is turned)
3. The Audio unit, Navigation display, RES display, DVD player (confirmation as any one component is disconnected)

Scheme 12

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 below.

Note. Key cylinder switch tests require a second key be used to perform.

Scheme 13

Scheme 14

Scheme 15

* 1. The multiplex system should flash the ignition key light and sound the beeper each time when the key is turned to the LOCK or UNLOCK position, and should not flash/beep as the key is returned to the neutral position.

Did the multiplex control system confirm all the circuits by flashing the ignition key light and sounding the beeper?

1. YES: The multiplex system is OK. If the symptom is still present, go to the input test for the system with the problem (see these items), or refer to multiplex input test (see «Multiplex Control Unit Input Test»(ref-171523-S42043903642005020700000) ). Power door locks (see «CONTROL UNIT INPUT TEST»(ref-171859-S03766649362005021400000) ) Security (EX models) (see «CONTROL UNIT INPUT TEST»(ref-171859-S03766649362005021400000) ) Keyless (EX models) (see «CONTROL UNIT INPUT TEST»(ref-171859-S03766649362005021400000) ) Power windows (includes key-off timer operation) (see «CONTROL UNIT INPUT TEST»(ref-171455-S03538664252005020400000) ) Entry light control, Key light timer (see «CONTROL UNIT INPUT TEST»(ref-171726-S18808478972005021000000) ) Windshield wiper controls (front and rear) (see «REAR WINDOW INTERMITTENT WIPER CONTROL UNIT INPUT TEST»(ref-153751-S08883250042003042300000) ) Automatic lights off (EX models) (see «CONTROL UNIT INPUT TEST»(ref-171510-S20111062492005020700000) ) Reminder chimes (Key-in, seat belt, lights-on) (see «CONTROL UNIT INPUT TEST»(ref-171510-S20111062492005020700000) ) Dash lights brightness control (see «CONTROL UNIT INPUT TEST»(ref-171726-S42007759002005021000000) ) Engine oil pressure indicator (see «CONTROL UNIT INPUT TEST»(ref-171510-S20111062492005020700000) )
2. 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.

Scheme 16

1. Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box.
2. Carefully pry off driver's door switch trim (see «FRONT DOOR PANEL REMOVAL/INSTALLATION»(ref-171352-S12700656352005020200000) ).
3. Disconnect door multiplex connector A (20P).
4. Check for continuity between No. 2 terminal of the driver's under-dash fuse/relay box socket and No. 15 terminal of the door multiplex control unit connector A (20P). Is there continuity? YES: Replace the multiplex control unit most closely related to failure. NO: Repair an open in the wire between the door multiplex connector and the driver's under-dash fuse/relay box. If the wire is OK, replace the under-dash fuse/relay box.

Scheme 17

1. Disconnect driver's multiplex control unit connector B (22P).
2. Disconnect passenger's multiplex control unit connector B (22P).
3. Check for continuity between No. 1 terminal of the driver's multiplex connector B (22P) and No. 9 terminal of the passenger's multiplex connector B (22P). Is there continuity? YES: Replace the multiplex control unit most closely related to the failure. NO: Repair an open in the wire between the door multiplex B (22P) connector and the passenger's multiplex B (22P) connector.

Scheme 18

Scheme 19

1. Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box.
2. Carefully pry off the driver's door switch trim (see «FRONT DOOR PANEL REMOVAL/INSTALLATION»(ref-171352-S12700656352005020200000) ).
3. Disconnect door multiplex connector A (20P).
4. Disconnect passenger's multiplex control unit connector B (22P).
5. Check for continuity between No. 15 terminal of door multiplex connector A (20P) and body ground. Is there continuity? YES: Repair short to ground in the wire between door multiplex control unit connector A (20P) and the driver's under-dash fuse/relay box. NO: Go to step 6.
6. Check for continuity between No. 9 terminal of passenger's multiplex connector B (22P) and body ground. Is there continuity? YES: Repair short to ground in the wire between passenger's multiplex control unit connector B (22P) and driver's multiplex control unit connector B (22P). NO: Replace driver's multiplex control unit and recheck the symptom.

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

1. Remove the driver's door panel (see «FRONT DOOR PANEL REMOVAL/INSTALLATION»(ref-171352-S12700656352005020200000) ), and disconnect the connectors from the door multiplex control unit.
2. 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 3. NOTE: The illustration shows '99 models.
3. Make the following input tests at connector A (20P). If any test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, go to step 8 . Driver's Unit
4. Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box, and disconnect its connectors.
5. 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 6.
6. Make the following input tests at the connector B and fuse/relay box socket. If any test indicate a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, go to step 7. Passenger's Unit
7. Remove the passenger's multiplex control unit from the passenger's under-dash fuse/relay box, and disconnect its connector.
8. 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 9.
9. Make the following input tests at the connector B and the fuse/relay box socket. If any test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, go to the Multiplex Control System Troubleshooting (see «Troubleshooting»(ref-171523-S27246425402005020700000) ).

Scheme 25