Multiplex Control Systems: Description

WARNING: Deactivate air bag system before performing any service operation. See appropriate AIR BAG RESTRAINT SYSTEMS article. DO NOT apply electrical power to any component on steering column without first deactivating air bag system. Air bag may deploy.

CAUTION: Before disconnecting battery, obtain anti-theft code for radio. After battery is reconnected, the word CODE will appear on radio display. Enter 5-digit anti-theft code using select buttons and radio will begin working. If code is entered wrong 10 times, leave radio on at least one hour and enter code correctly. Any time radio power is disconnected, pre-selected radio stations will have to be reset.

Multiplex control system incorporates 4 internal functions. Fail-safe function, fixes or ignores faulty signals. Multiplexing function sends multiple signals over a set of shared wires. Self-diagnostic function provides mode one to diagnose system components and mode 2 to diagnose multiplex control system, or input lines. Wake up/sleep function, provides full power only when requested to reduce battery draw.

Multiplex control system consists of a driver, passenger, and door multiplex control units. These 3 control units integrate independent control units using multiplex communication lines. See Fig 1 .

Driver's multiplex control unit is located behind driver's side kick panel. Passenger's multiplex control unit is located behind passenger's side kick panel. Door multiplex control unit is located in driver's door and is incorporated in power window master switch.

Multiplex integrated control system includes engine oil pressure indicator, seat belt reminder circuit, lights-on and key-in reminder circuits. Other controlled systems include the Driving Position Memory (DPM) system, key light timer, dash illumination brightness control, entry illumination, power door locks (with keyless entry), power windows (with key-off timer operation), wiper/washers (with speed respondent intermittent wiper), security alarm system and interlock system.

Fig 1: Locating Multiplex Control System Components

Courtesy of AMERICAN HONDA MOTOR CO., INC.