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Multiplex Control System: Diagnosis Honda Accord VI

Communication Devices 9 illustrations ~2353 words

Troubleshooting

Special Tools Required

SCS Service Connector 07WAZ-001010A

Scheme 3

Scheme 3: Troubleshooting
Scheme 3: Troubleshooting

Scheme 4

Scheme 4
Scheme 4

Scheme 5

Scheme 5
Scheme 5
  1. Check the No. 9 (7.5A) 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. Is 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 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. Check self-diagnosis function Mode 1 for a diagnostic trouble code (DTC). 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. If the system enters Mode 1, go to step 5. If the system does not enter Mode 1, see if the SCS circuit is working properly. Go to step 6 .
  5. About 1 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 a code, it will blink/beep, pause, then repeat the code as long as the ignition switch is ON (II). If there is more than one DTC, the system will indicate them in ascending order, beginning from the DTC with the lowest numerical value. Does the ignition key light blink and the beeper beep? YES -There is a DTC. Count the blinks/beeps to find your DTC in the table, then go to step 9 and check the communication lines. DTC IDENTIFICATION DTC Cause 1 The driver's unit is not able to receive signals from the door unit. 2 The driver's unit is not able to receive signals from the passenger's unit. 3 Malfunction in the driver's unit. 4 Signals from each unit do not match. (LX and EX control units are not interchangable) 5 The passenger's unit is not able to receive signals from the other units. 6 The door unit is not able to receive signals from the other units. NO -If the system goes into Mode 1 as described in step 4 , and there is not repeating DTC. Go to step 11 .
  6. Remove the special tool from the SCS connector.
  7. Check for continuity between the No. 1 terminal of the inspection connector and the A15 terminal in the driver's multiplex control unit. Is there continuity? YES -Go to step 8. NO -Replace the driver's under-dash fuse/relay box, and recheck for DTC's.
  8. Check for continuity between the No. 3 terminal of the inspection connector and body ground G401. Is there continuity? YES -If there is still no Mode 1 confirmation, replace the driver's multiplex control unit and try again. After replacing the driver's multiplex control unit the system confirms Mode 1 and there are no codes, go to step 12 . NO -Repair open in the wire, and recheck for DTC's.
  9. With the ignition switch OFF, check for continuity according to the table. CONTINUITY CHECK Communication Line Wire Continuity Door unit to Driver's unit BRN YES Driver's unit to Passenger's unit PNK YES Is there continuity? YES -Go to step 10. NO -Check for an open in the wire.
  10. Turn the ignition switch ON (II), and check for voltage between the communication line and ground. VOLTAGE CHECK Communication Line Wire Voltage Door unit to Driver's unit BRN 3.5-9.5 Driver's unit to Passenger's unit PNK 3.0-10.0 Does the voltage match the table? YES -Communication lines are OK. Go to step 11. NO -Repair the line according to the following. If the voltage is too high: Check for a short to another wire with voltage. Check for poor contact in the connectors at each control unit connector to the wire. If the voltage is too low: Check for a short to ground or to another wire. Check for poor connections at each control unit connector to the wire. Faulty circuit in one of the multiplex control units connected to the wire. If any one or all the control units are completely inoperative, perform the multiplex control unit input test (see «Multiplex Control Unit Input Test»(ref-178653-S35805370002005061800000) ).
  11. Shift to the sleep mode: Turn the ignition switch OFF and remove the key. Remove the special tool from the SCS connector. 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 1 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). Go to step 12.
  12. Confirm the sleep mode: Check for voltage to ground on the BRN wire and PNK wire. There should battery voltage in the sleep mode. Check the parasitic draw at the battery while shifting to the sleep mode. Amperage should change from about 70 to 80 mA to less than 20 mA. If the vehicle does not go into the sleep mode, carefully perform Mode 2 test (see step 14 ), and check for faulty input for example a key cylinder switch keeping the system awake.
  13. Confirm the wake up mode. When any switch in the multiplex system is turned on, it wakes up its related control unit which, in turns wakes up the other units. After one minute it will return to sleep mode again If the switch is returned to the original position. When the ignition switch is turned ON (II), all of the multiplex control units wake up at the same time without "talking" to each other through the communication lines. If the wake up mode is confirmed on the first switch tested, and there is no problem with any other switch operation, the system is working correctly. Go to step 14. After confirming a problem in sleep mode, look in the following tables for the switch most closely related to the problem you may be having. Operate that switch and see if its control units wake up. Also use Mode 2 step 14 to confirm switch inputs. NOTE: If any control unit is faulty and will not wake up, several functions (locks, windows, etc.) of the system will malfunction at the same time. In each table below, the control unit is followed by a list of the switches and input signals that can wake it up. Multiplex Control Unit, Passenger's: No. 9 (7.5A) Driver's Fuse, No. 13 (7.5A) Passenger's Fuse Communication lines (BRN, PNK) Front passenger's door lock knob switch (LOCK) Front passenger's key cylinder switch (LOCK) Front passenger's door lock knob switch (UNLOCK). When testing the passenger's door lock knobs, be sure all other passenger lock knobs are in the locked position. Front passenger's key cylinder switch (UNLOCK) Front passenger's door lock switch (LOCK/UNLOCK) Front passenger's door switch (OPEN) Right rear door switch (OPEN) Right rear door lock knob switch (UNLOCK). When testing the passenger's door lock knobs, be sure all other passenger lock knobs are in the locked position. Keyless transmitter (LOCK) Keyless transmitter (UNLOCK) Keyless transmitter (TRUNK) Security input for the radio. Test by disconnecting and reconnecting the radio connector. Multiplex Control Unit, Driver's: No. 9 (7.5A) Driver's Fuse, No. 13 (7.5A) Passenger's Fuse Communication lines (BRN, PNK) Combination switch Driver's door switch (OPEN) Left rear door switch (OPEN) Left rear door lock knob switch (UNLOCK) Trunk latch switch (OPEN) Trunk key cylinder switch (UNLOCK) Engine hood switch (OPEN) Multiplex Control Unit, Door: No. 9 (7.5A) Driver's Fuse, No. 13 (7.5A) Passenger's Fuse Communication lines (BRN, PNK) Driver's door lock knob switch (LOCK) Driver's door key cylinder switch (LOCK) Driver's door lock knob switch (UNLOCK) Driver's door key cylinder switch (UNLOCK) Driver's door lock switch (LOCK/UNLOCK)
  14. With the system in Mode 1, and the ignition switch still in the ON (II) position, disconnect the special tool from the multiplex control inspection connector for about 5 to 10 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. Go to step 15. Mode 2: NOTE: To cancel Mode 2, disconnect the SCS service connector from the multiplex control inspection connector for 10 seconds or more, or turn the ignition switch OFF.
  15. Look in the following tables for the switch most closely related to the problem. Test all the switches in the following order, otherwise the test results maybe inaccurate. While still in Mode 2, operate that switch to test the wire, switch, and its control unit input. 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. Test the other switches. NO -Go to step 16. In each of the following tables, the control unit is followed by list of circuits that it can check in Mode 2. A second key is necessary to test the key cylinder switches. If only one key is available, cut a second key from a non-immobilizer type key blank for the test. Multiplex Control Unit, Passenger's Test Table Multiplex Control Unit, Passenger's; Test all the switches in the following order, otherwise the test results may be inaccurate: Front passenger's door lock knob switch (LOCK) Front passenger's key cylinder switch (LOCK) Front passenger's door lock knob switch (UNLOCK). When testing the passenger's door lock knobs, be sure all other passenger lock knobs are in the locked position. Front passenger's key cylinder switch (UNLOCK) Front passenger's door lock switch (UNLOCK/LOCK) Right rear door lock knob switch (UNLOCK). When testing the passenger's door lock knobs, be sure all other passenger lock knobs are in the locked position. Front passenger's door switch (OPEN) Right rear door switch (OPEN) Keyless transmitter (LOCK) Keyless transmitter (UNLOCK) Keyless transmitter (TRUNK) Security input for the radio. Test by disconnecting and reconnecting the radio connector. Multiplex Control Unit, Driver's Test Table Multiplex Control Unit, Driver's Dash lights brightness controller (ROTATE) Driver's door switch (OPEN) Left rear door switch (OPEN) Left rear door lock knob switch (UNLOCK) Trunk latch switch (OPEN) Trunk key cylinder switch (UNLOCK) Driver's seat belt switch (BUCKLED) Windsheild wiper/washer switch (except MIST switch) Brake pedal position switch (Brake switch) (PRESSED) Parking brake switch (ON) Hood switch (OPEN) Headlight or combination switch (ON) Multiplex Control Unit, Door Test Table Multiplex Control Unit, Door; Test all the switches in the following order, otherwise the test results maybe inaccurate: Driver's door lock knob switch (LOCK) Driver's key cylinder switch (LOCK) Driver's door lock knob switch (UNLOCK) Driver's key cylinder switch (UNLOCK) Driver's door lock switch (LOCK/UNLOCK) Power window master switch (not the passenger's switches) The key cylinder switches should only beep/flash when turned to LOCK or UNLOCK. If they beep/flash when returning to the center position, the switch is defective or misaligned. Adjust or replace the affected key cylinder switch.
  16. Check 2 or 3 more circuits listed for that control unit. Does the ignition key light blink and the beeper beep for each additional circuit? YES -The additional circuits are OK. Repair the short or open in the circuit that failed the test in the proceeding step. Refer to the test(s) for that individual system. 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 stem works properly, the original control unit is faulty; replace it. If there is still a malfunction, substitute a known-good control unit for the next most likely faulty control unit, then recheck. If the stem works properly, that control unit is faulty; replace it.

Multiplex Control Unit Input Test

Note. If the multiplex control unit is replaced, never use a multiplex control unit other than the one which is manufactured by the original multiplex control unit maker. Using other multiplex control units, manufactured by a non-original maker could cause a malfunction of communication among the multiplex control unit.

Door Unit

Scheme 6

Scheme 6: Multiplex Control Unit Input Test
Scheme 6: Multiplex Control Unit Input Test

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Scheme 7

Scheme 8

Scheme 8
Scheme 8

Scheme 9

Scheme 9
Scheme 9

Scheme 10

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Scheme 10

Scheme 11

Scheme 11
Scheme 11
  1. Remove the driver's door panel, 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.
  3. Make the following input tests at connector A. If a test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, go to step 4. Passenger's Unit: Remove the passenger's multiplex control unit from the passenger's under-dash fuse/relay box. 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. Make the following input tests at connector B and the fuse/relay box socket. If a test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, go to step 7. Driver's Unit: Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box. 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. Make the following input tests at connector B and the fuse/relay box socket. If a test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, troubleshoot the Multiplex Control System (see «Troubleshooting»(ref-178653-S13041513642005061800000) ).

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