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The Legend is equipped with a 16bit ECU manufactured by Matsushita Industries in Japan (better known for it's subsidiary in the US, Panasonic) for Honda Motor Company. It is equivalent to other Honda OBD1 setups in that it uses the same wiring connectors and wiring layout. Unlike the OBD1 Civic and Integras, there is no external provision for code scanning or datalogging. On automatic transmission cars, the transmission control unit (TCU) is integrated on a separate daughter board in the ECU case. When equipped with an automatic, the engine computer is referred to by Honda as a PCM (power train control module) instead on an ECM (engine control module).

US Models have the following input sensors:

  • HO2S Left oxygen sensor
  • HO2S Right oxygen sensor
  • MAP sensor
  • CKP 1 crank sensor position 1
  • CYP 2 crank sensor position 2
  • CYP 1 cylinder sensor position 1
  • CYP 2 cylinder sensor position 2
  • KS Left Knock Sensor
  • KS Right Knock Sensor
  • EGR valve lift sensor
  • Atmospheric pressure/barometer
  • VSS Speed sensor
  • TPS Throttle position
  • PSP Power Steering Pressure (idle up)
  • ECT Engine coolant temp
  • IAT Air Intake temp
  • Ignition timing adjuster
  • Clutch switch, negative input
  • Neutral switch,
  • Brake switch, positive input
  • Starter signal, positive input
  • Service check connector, negative input


  • Main relay
  • Reverse lockout relay
  • EGR control solenoid (pwm), negative output
  • Fuel pressure regulator solenoid, negative output
  • VIS high solenoid
  • Vis low solenoid
  • Pair valve solenoid
  • MIL Check engine light
  • Fuel Injectors 1-6, negative switched output
  • Ignition control module
  • Left and Right oxygen sensor heaters
  • IAC Idle Air Control Valve
  • Alternator Field
  • Oxygen sensor heaters
  • Fan control unit
  • A/C clutch
  • Tachometer
  • EVAP purge solenoid valve

The ECU went through a major revision in 1993 with a revised main board and auto transmission board. The coding in the chip changed

Main Board Layout

IC 401 Microprocessor (MCU)

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