Multiplex Control Systems: Other Honda Prelude V

DOOR MULTIPLEX CONTROL UNIT

Unit is located in driver's door and is incorporated in power window master switch.

DRIVER'S MULTIPLEX CONTROL UNIT

Unit is located on fuse/relay block behind driver-side kick panel.

PASSENGER'S MULTIPLEX CONTROL UNIT

Unit is located on fuse/relay block behind passenger-side kick panel.

Multiplex control system includes a multiplex function, wake-up/sleep function, fail-safe function, and a 2-mode self-diagnostic function. Self-diagnostic Mode 1 is used to diagnose multiplex control system. Self-diagnostic Mode 2 is used to diagnose a failure in input line of each system.

Multiplex integrated control system includes engine oil pressure indicator flasher circuit, seat belt reminder circuit, and lights-on and key-in reminder circuits. Other controlled systems include dash illumination brightness control, entry illumination, power door locks, power windows, wiper/washers, rear window defogger and interlock system.

Scheme 2

MULTIPLEX COMMUNICATION FUNCTIONS

Multiplex control system reduces the number of wire harnesses by sending digital signals over shared multiplex communication lines. A Central Processing Unit (CPU) converts input signals from each switch to digital signals, and transmits these as serial data signals. Transmitted serial data signals from multiplex control units are converted to switch signals for switch operation. There are dedicated communication lines between multiplex control units. From driver's door unit to driver's multiplex control unit (Brown wire), from driver's to passenger's multiplex control units (Light Green wire), and from passenger's to driver's multiplex control units (Pink wire). See WIRING DIAGRAMS .

WAKE-UP & SLEEP FUNCTIONS

To decrease parasitic draw on battery when ignition is off, wake-up and sleep modes are used. In sleep mode, multiplex control unit stops communication and CPU control functions when system operation is not needed. When any monitored system or switch operates, such as a door being unlocked, the related multiplex control unit will change from sleep function to wake-up function. A wake-up signal is then sent to other multiplex control units. When ignition switch is turned off, there is a 10-second delay before sleep mode begins. Sleep mode will not begin if any door is open.

FAIL-SAFE FUNCTIONS

To prevent improper operation, the multiplex system has a fail-safe function. In fail-safe mode, output signals will use default values until fault is corrected (i.e. faulty control unit or communication line). Each multiplex control unit has hardware fail-safe output signal defaults when there is a CPU failure. There are also software fail-safe defaults that ignore faulty multiplex control unit signals and allows system to continue to function.

SYSTEM TESTS

PRELIMINARY TESTS

1. Ensure fuse No. 13 (13-amp), located in fuse/relay block behind left kick panel and fuse No. 43 (7.5-amp), located in underhood fuse/relay block are okay. If fuse(s) are not okay, find and repair cause of blown fuse. See «WIRING DIAGRAMS»(ref-32689-S13880314082001101600000) . If fuse(s) are okay, perform appropriate MULTIPLEX CONTROL UNIT test. Repair as necessary. After repairs, go to next step.
2. Check for Diagnostic Trouble Codes (DTCs). See RETRIEVING DIAGNOSTIC TROUBLE CODES (DTCs) under «SELF-DIAGNOSTIC MODE 1 TESTS»(ref-32689-S02798592432001101600000) . Repair as necessary. If no DTC is indicated, go to «WAKE-UP FUNCTION TESTS»(ref-32689-S15194427842001101600000) .

Remove driver's door trim panel enough to gain access to door multiplex control unit connector. Turn ignition off. Disconnect door multiplex control unit 20-pin harness connector. (Scheme 3) Check connector terminals and contacts. Repair as necessary and retest system. If connector terminals and contacts are okay, perform input tests. (Scheme 3) If test results are as specified, replace power window master switch. See REMOVAL & INSTALLATION.

Scheme 3

Turn ignition off. Remove driver's multiplex control unit from fuse/relay block behind left kick panel. (Scheme 4) Check terminals and contacts. Repair as necessary and retest system. If terminals and contacts are okay, perform input tests. (Scheme 4) If test results are as specified, replace driver's multiplex control unit (mounted on fuse/relay block). See REMOVAL & INSTALLATION.

Scheme 4

Turn ignition off. Remove passenger's multiplex control unit from fuse/relay block behind right kick panel. (Scheme 5) Check terminals and contacts. Repair as necessary and retest system. If terminals and contacts are okay, perform input tests. (Scheme 5) If test results are as specified, replace passenger's multiplex control unit (mounted on fuse/relay block). See REMOVAL & INSTALLATION.

Scheme 5

Driver's-To-Passenger's Multiplex Control Unit

1. Turn ignition off. Check continuity in communication line between driver's multiplex control unit harness connector terminal B1 (Pink wire) and passenger's multiplex control unit harness connector terminal B9 (Pink wire). See «WIRING DIAGRAMS»(ref-32689-S13880314082001101600000) . If continuity exists, go to next step. If continuity does not exist, repair open in Pink wire. After repairs, recheck DTCs.
2. Turn ignition on. Check voltage in communication line between ground and driver's multiplex control unit harness connector terminal B1 (Pink wire) and passenger's multiplex control unit harness connector terminal B9 (Pink wire). See «WIRING DIAGRAMS»(ref-32689-S13880314082001101600000) . Voltage should be 3-10 volts. If voltage is not as specified, go to next step.
3. If voltage is greater than 10 volts, check for short in circuit or poor contact or faulty circuit at connector on receiver side of unit. If voltage is less than 3 volts, check for short to ground or short to another wire in circuit. Check for poor contact or faulty circuit at connector on transmit side of unit. Repair as necessary. After repairs, recheck DTCs.

Passenger's-To-Driver's Multiplex Control Unit

1. Turn ignition off. Check continuity in communication line between passenger's multiplex control unit harness connector terminal B1 (Pink wire) and driver's multiplex control unit harness connector terminal D1 (Pink wire). See «WIRING DIAGRAMS»(ref-32689-S13880314082001101600000) . If continuity exists, go to next step. If continuity does not exist, repair open in Pink wire. After repairs, recheck DTCs.
2. Turn ignition on. Check voltage in communication line between ground and passenger's multiplex control unit harness connector terminal B1 (Pink wire) and driver's multiplex control unit harness connector terminal D1 (Pink wire). See «WIRING DIAGRAMS»(ref-32689-S13880314082001101600000) . Voltage should be 3-10 volts. If voltage is not as specified, go to next step.
3. If voltage is greater than 10 volts, check for short to another circuit or poor contact or faulty circuit at connector on receiver side of unit. If voltage is less than 3 volts, check for short to ground or short to another wire in circuit. Check for poor contact or faulty circuit at connector on transmit side of unit. Repair as necessary. After repairs, recheck DTCs.

Shifting To Sleep Mode

Turn ignition off. Open and close one of the doors to cancel key off operation timer in power window system. Ensure trunk is closed and exterior lights are off. Multiplex control system will shift to sleep mode after one minute, if switches related to multiplex control unit are not operated. All switches must be in OFF position, except door lock knob switches, ignition key switch, audio unit (radio) switch, and hood switch.

Confirming Sleep Mode

1. Check for voltage on driver's and passenger's multiplex control unit wake-up communication line (Brown wire for door-to-driver's control unit; Pink and Light Green wire for driver's-to-passenger's control unit). See «WIRING DIAGRAMS»(ref-32689-S13880314082001101600000) .
2. If sleep mode is off, voltage on communication line will be zero. If sleep mode is on, voltage (3.5-9.5 volts for door-to-driver's control unit; 4.0-10.5 volts for driver's-to-passenger's control unit; 3-10 volts for passenger's-to-driver's control unit) will be present on communication line. See «IDENTIFYING COMMUNICATION LINE & LINE VOLTAGE»(ref-32689-S20533869742001101600000) table.
3. Check voltage between each multiplex control unit communication line and ground while shifting to sleep mode. See «IDENTIFYING COMMUNICATION LINE & LINE VOLTAGE»(ref-32689-S20533869742001101600000) table. There should be zero volts at each communication line when changing to sleep mode.
4. Check parasitic draw at battery while changing to sleep mode. Parasitic draw should change from 70-80 milliamps to less than 10 milliamps.

IDENTIFYING COMMUNICATION LINE & LINE VOLTAGE

Confirming Wake-Up Mode

After confirming sleep mode, turn each of the following switches to ON position and wake up each multiplex control unit.

Door multiplex control unit switches

1. Driver's door lock switch (LOCK/UNLOCK).
2. Driver's door key cylinder switch (UNLOCK).
3. Driver's door lock knob switch (LOCK/UNLOCK).

Driver's multiplex control unit switches

1. Door-to-driver's communication line (BRN).
2. Passenger's-to-driver's communication line (PNK).
3. Combination light switch.
4. Driver's door switch.

Passenger's multiplex control unit switches

1. Driver's-to-passenger's communication line (LT GRN).
2. Passenger's door switch.
3. Passenger's door key cylinder switch (LOCK/UNLOCK).
4. Passenger's door lock switch (LOCK/UNLOCK).

If all applications operate properly, wake-up mode is okay. If any multiplex control unit is faulty and cannot wake up, several parts of multiplex system will not operate.

Switching To Mode 2

1. To enter self-diagnostic Mode 2, vehicle must be in self-diagnostic Mode 1. See «SELF-DIAGNOSTIC MODE 1 TEST»(ref-32689-S02798592432001101600000) . To switch from Mode 1 to Mode 2, disconnect SCS service connector for 5-10 seconds, then reconnect SCS service connector again. To cancel Mode 2, remove SCS service connector for 10 seconds or longer or turn ignition off.
2. Activate Mode 2 and operate each switch controlled by each multiplex control unit, see steps 3) through 5). If the related circuit line of the switch operates okay, ignition key light and ceiling light will flash once and buzzer will sound once. If circuit is faulty, there will be no system operation when switch is operated. For diagnostic and repair procedures of items listed below, see appropriate ACCESSORIES & EQUIPMENT article in the ACCESSORIES/SAFETY EQUIPMENT section.
3. Door multiplex control unit switches: Driver's door lock switch (LOCK/UNLOCK). Driver's door key cylinder switch (UNLOCK). Driver's door lock knob switch. Power window master switch.
4. Driver's multiplex control unit switches: Backup light switch. Combination light switch. Driver's door switch. Driver's seat belt switch. Generator "L" terminal. Rear window defogger switch. Wiper/washer switch (except MIST switch).
5. Passenger's multiplex control unit switches: Passenger's door switch. Passenger's door lock switch (LOCK/UNLOCK). Instrument panel light brightness controller. Intermittent wiper/washer switch.

INSTRUMENT PANEL FUSE/RELAY BLOCK (LEFT OR RIGHT SIDE)

Note. Obtain anti-theft security code for radio from vehicle owner. List frequencies for radio preset buttons before disconnecting battery.