Multiplex Control Unit

Control Unit Input Test

NOTE: If the power window cannot be operated by its own window switch, the problem is not a multiplex control unit. Troubleshoot power or ground to the window switch or motor.

Passenger's Unit
1. Before testing the power window control functions, troubleshoot the multiplex control system.
2. Remove the passenger's multiplex control unit from the passenger's under-dash fuse/relay box, and disconnect its connector.




3. 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 4.




4. With the passenger's multiplex control unit still disconnected, make these input tests at the passenger's under-dash 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 step 5.

Driver's Unit
5. Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box.




6. Inspect all 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 7.




7. With the driver's multiplex control unit still disconnected, make these input tests at the driver's under-dash 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 step 8.

8. Remove the passenger's multiplex control unit from the passenger's under-dash fuse/relay box and connect fuse/relay box socket terminal A12 to battery voltage. This turns the power window relay on.




9. With the driver's multiplex control unit still disconnected, make these input tests at the driver's under-dash fuse/relay box socket.
- If any test indicates a problem, find and correct the cause, then recheck the system.
- If the input test proves OK, go to step 10.




10. Reconnect the driver's multiplex control unit to the driver's under-dash fuse/relay box, turn the ignition switch ON (II) to keep the system awake, and perform the given input tests at the appropriate connectors on the back of the driver's under-dash fuse/relay box. For driver's under-dash fuse/relay box connector socket location.
- 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 11.

Door Unit
11. Remove the door multiplex control unit from the driver's door, and disconnect its connectors.




12. 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 13.




13. With the door multiplex control unit still disconnected, make these input tests at the connectors.
- 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 14.




14. If all the input tests prove OK, one of the control units must be faulty. Substitute a known-good control unit for the one that is most likely at fault using the chart, then check the system. If the system 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 unit to be at fault, and recheck. If the system works properly, the original unit is faulty; replace it.