LEMON Manuals: Even more car manuals for everyone
Home >> Acura >> 2002 >> MDX Base, MGHA >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Multiplex Control Systems >> System Tests >> Self-Diagnostic System

Self-Diagnostic System

  1. Ensure fuse No. 9 (10-amp) in driver's underdash fuse/relay box and fuse No. 13 (7.5-amp) in passenger's underdash fuse/relay box are okay. If fuse(s) are not okay, find and repair cause of blown fuse. See WIRING DIAGRAMS  . If fuse(s) are okay, go to next step.
  2. Locate multiplex control unit diagnostic test connector under steering column, taped to brake switch wiring harness. See Fig 1 . Turn ignition on. Connect SCS Service Connector (07WAZ-001010A) to multiplex control unit diagnostic test connector and wait for at least 5 seconds.
    Fig 1: Entering Self-Diagnostic Mode
    G00029367Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. Observe ignition switch light and buzzer. They should come on for 2 seconds, then off for .2 seconds, then back on again for .2 seconds. This confirms that you are in MODE 1 of self-diagnostics function. After entering MODE 1, go to next step. If ignition switch light and buzzer do not operate as specified, go to step  5 .
  4. If a DTC is present, ignition switch light and buzzer will indicate DTC by the number of times they turn on and off. If a DTC is indicated, go to step  7 . If no DTCs are indicated, go to next step.
  5. Check continuity between multiplex control unit diagnostic test connector and driver's multiplex control unit terminal A15 (Light Blue wire). See WIRING DIAGRAMS  . If continuity exists, go to next step. If continuity does not exist, repair open circuit in wiring. If wiring is okay, replace driver's underdash fuse/relay block. After repairs, recheck for DTCs.
  6. Check continuity between ground and Black wire at multiplex control unit diagnostic test connector. If continuity is indicated, go to step  13 . If continuity is not indicated, repair open circuit to ground in Black wire. After repairs, recheck for DTCs.
  7. One second after entering MODE 1, ignition switch light flashes and buzzer sounds to indicate DTC is present. If more than one DTC is present, system will indicate them in ascending order and will repeat every 3 seconds. See DTC DIAGNOSIS  table. Note DTC(s) and go to next step.
    DTC DIAGNOSIS

    DTC Probable Cause
    1 (1) Driver's Control Unit Can Not Receive Signal From Door Control Unit
    2 (1) Driver's Control Unit Can Not Receive Signal From Passenger's Control Unit
    3 (1) Driver's Control Unit Can Not Receive Signal From Power Seat Control Unit (DPMS)
    4 (1) Not A Valid Code
    5 (2) Malfunction In Driver's Control Unit
    6 (1) Door Control Unit Can Not Receive Signals From Other Control Units
    7 (1) Passenger's Control Unit Can Not Receive Signals From Other Unit
    (1) Diagnose using COMMUNICATION LINES  under CIRCUIT TESTS.
    (2) Replace driver's multiplex control unit and recheck DTCs.
  8. Turn ignition off. Check communication lines for continuity. See COMMUNICATION LINE CONTINUITY  . If continuity is not present on either wire, repair open circuit between control units. If continuity exists on both circuits, go to next step.
    COMMUNICATION LINE CONTINUITY

    Communication Line Wire Color
    Door Unit To Driver's Unit Brown
    Driver's Unit To Passenger's Unit Or Power Seat Unit Pink
  9. Turn ignition switch on. Test for appropriate voltages at control units. See COMMUNICATION LINE VOLTAGE  . If voltages are correct, communication lines are okay. Go to next step. If voltages are incorrect, check for open or short circuit in communication line, poor connection at either control unit or faulty circuit in transmitting unit.
    COMMUNICATION LINE VOLTAGE

    Communication Line (Wire Color) Voltage
    From Door Control Unit To Driver's Control Unit (Brown Wire) 3.5-9.5
    From Driver's Control Unit To Passenger's Control Unit Or Driver's Power Seat Control (DPMS) Unit (Pink Wire) 3.0-10.0
  10. Shift system to SLEEP mode. Turn ignition off. Open and close a door to cancel key off operation timer in power window system. Ensure all doors are closed and exterior lights are off. If switches related to multiplex control unit are not operated, multiplex control system will shift to SLEEP mode after one minute. All switches must be in OFF position, except door lock knob switches. Go to next step.
  11. Confirm SLEEP mode. Check for voltage on multiplex control unit wake-up communication lines (Brown wire for door-to-driver's control unit; Pink wire from driver's, passenger's or driver's power seat control unit). See WIRING DIAGRAMS  . Battery voltage should be present. Check parasitic draw at battery while changing to sleep mode. Parasitic draw should change from 70-80 milliamps to less than 10-20 milliamps.
    12. NOTE: When ignition is turned on, all multiplex control units wake up at the same time, without talking to each other. When any switch in multiplex system is turned on, it wakes up its corresponding control unit, which in turn wakes the other control units. If any multiplex control unit is faulty and cannot wake up, several parts of multiplex system will not operate.
  12. Confirm WAKE UP mode. After confirming sleep mode, look at the following lists for switch most closely associated with the problem. Operate switch to see if its corresponding control unit wakes up.

    Passenger's multiplex control unit switches:

    • Front passenger's door switch.
    • Front passenger's key cylinder switch (LOCK/UNLOCK).
    • Front passenger's door lock switch (LOCK/UNLOCK).
    • Front passenger's door lock knob switch (UNLOCK).
    • Power mirror switch (DPMS).
    • Right rear door lock knob switch (UNLOCK).
    • Security input for radio and navigation unit (disconnect radio connector to test).

    Driver's multiplex control unit switches:

    • Ignition key switch (insert key).
    • Headlight switch.
    • Park/taillight switch.
    • Driver's door switch.
    • Left rear door switch.
    • Tailgate latch switch.
    • Engine hood switch.
    • Keyless entry transmitter (LOCK).
    • Keyless entry transmitter (UNLOCK).
    • Keyless entry transmitter (PANIC).

    Door multiplex control unit switches:

    • Driver's door key cylinder switch (LOCK/UNLOCK).
    • Driver's door lock knob switch (LOCK/UNLOCK).
    • Driver's door lock switch (LOCK/UNLOCK).
    • Position 1 switch (DPMS).
    • Position 2 switch (DPMS).
    • Power window master switch.

    If all components operate properly, WAKE UP mode is okay. Go to next step. If WAKE UP mode does not function, test power and ground inputs to all 3 multiplex control units. See DOOR MULTIPLEX CONTROL UNIT  ,DRIVER'S MULTIPLEX CONTROL UNIT  and PASSENGER'S MULTIPLEX CONTROL UNIT  under PIN VOLTAGE TESTS. Repair as necessary.

    13. NOTE: To enter self-diagnostic MODE 2, vehicle must already be in self-diagnostic MODE 1. To cancel MODE 2, remove SCS service connector for at least 10 seconds or turn ignition off.
  13. Activate MODE 2 diagnostics. To switch from MODE 1 to MODE 2, disconnect SCS Service Connector (07WAZ-0010100) for 5-10 seconds, then reconnect SCS service connector. Ignition key light and beeper should come on for 2 seconds, then turn off and back on twice more at .2 second intervals. This confirms that system has gone from MODE 1 to MODE 2. Go to next step.
  14. Check the following lists and operate the switch most closely related to the problem.
    NOTE: When testing door lock knob, ensure that passenger's door lock knob is in LOCK position.

    Passenger's multiplex control unit switches:

    • Front passenger's door switch.
    • Front passenger's key cylinder switch (LOCK/UNLOCK).
    • Front passenger's door lock switch (LOCK/UNLOCK).
    • Front passenger's door lock knob switch (UNLOCK).
    • Power mirror switch (DPMS).
    • Right rear door switch.
    • Right rear door lock knob switch (UNLOCK).
    • Security input for radio and navigation unit (disconnect radio connector to test).

    Driver's multiplex control unit switches:

    • Brake light switch.
    • Instrument cluster lights brightness control.
    • Driver's door switch (OPEN).
    • Driver's seat belt switch (BUCKLED).
    • Hood switch (OPEN).
    • Engine oil pressure switch (DISCONNECTED/RECONNECTED).
    • Headlight switch (PARK/TAILLIGHT).
    • Ignition key switch.
    • Keyless entry transmitter (LOCK).
    • Keyless entry transmitter (UNLOCK).
    • Keyless entry transmitter (PANIC).
    • Parking brake switch.
    • Tailgate latch switch.
    • A/T gear position switch (PARK).
    • Windshield wiper/washer switch, except MIST switch.

    Door multiplex control unit switches:

    • Driver's door key cylinder switch (LOCK/UNLOCK).
    • Driver's door lock knob switch (LOCK/UNLOCK).
    • Driver's door lock switch (LOCK/UNLOCK).
    • Power window master switch.
    • Driving position memory switch (MEMO/POSITION 1/POSITION 2).

    DPMS-equipped vehicles:

    • Recline limit switch.
    • Driver's power seat adjustment (all directions).

    NOTE: Key cylinder switches should only beep or flash when turned to LOCK or UNLOCK position. If they beep or flash when returning switch to NEUTRAL position, switch is defective.

    If related circuit of switch operates properly, ignition key light will flash and buzzer will sound. Go to appropriate article in ACCESSORIES & EQUIPMENT to further diagnose problem. If circuit is faulty, there will be no system response when switch is operated. Go to next step.

  15. Check several other circuits listed for affected control unit. If ignition key light flashes and buzzer sounds when other switches are operated, repair short or open circuit to switch tested in previous step. Multiple failed circuits could mean that control unit has failed, even if DTC was not set. If several circuits have failed, substitute a known-good control unit, then recheck system. If there is still a malfunction, substitute a known-good control unit for next most likely failed control unit.
scientia non olet · About LEMON Manuals