The ECU - Electronic Control Unit is an embedded system that controls one or more of the electrical systems or subsystems in a vehicle.
ECU - Electronic Control Unit Connector.
The second-generation Mitsubishi Eclipse (1995–1999) was produced on the D31A, D32A, and D33A chassis and offered three engine variants: the 420A 2.0 L DOHC non-turbo, the 4G63 2.0 L DOHC turbocharged four-cylinder, and the 4G64 2.4 L SOHC unit. The engine control unit (ECU) manages multi-point fuel injection (MFI), ignition timing, idle speed control, and emission functions, with signal inputs from sensors and outputs to actuators across its multi-pin connector. The 2G Eclipse shares its D-series chassis platform with the Eagle Talon 2G (1995–1998), and the ECU connector pinout is identical between the two vehicles. Mitsubishi’s factory service manual (FSM) for the 1997 model year includes a “CHECK AT ECU TERMINALS” procedure detailing terminal numbers, circuit names, checking conditions, and reference voltage values.
| Pin | name | Signal |
|---|---|---|
| 10 | Ignition Control Module | Speed |
| 13 | Power Ground | Ground |
| 58 | Tachometer Output | RPM |
| 72 | Intake Air Temperature Sensor | Analog |
| 75 | Primary O2 Sensor | Analog |
| 76 | Secondary O2 Sensor | Analog |
| 83 | Engine Coolant Temperature Sensor | Analog |
| 84 | Throttle Position Sensor | Analog |
| 86 | Vehicle Speed Sensor | Speed |
| 87 | Throttle Position Switch | Analog |
| 90 | Mass Air Flow | Analog |
| 91 | Power Ground | Ground |
Notes
This table lists a representative subset of the ECU connector terminals. The full connector spans a larger pin count; unpublished terminals are not shown. The 4G63 turbo and 420A non-turbo variants use different ECU hardware with distinct connector configurations. Pins 13 and 91 are both power ground returns. The Mass Air Flow (pin 90) input is used on 4G63 turbo-equipped models; non-turbo variants may use a manifold absolute pressure (MAP) sensor in its place depending on specification.
Signals
- Ignition Control Module (pin 10) — speed/timing signal exchanged with the ignition control module for spark advance management
- Power Ground (pins 13, 91) — ECU power ground reference returns to engine block/chassis ground
- Tachometer Output (pin 58) — RPM pulse output signal driving the instrument cluster tachometer
- Intake Air Temperature Sensor (pin 72) — analogue voltage from the IAT sensor used for fuel and ignition correction based on inlet air density
- Primary O2 Sensor (pin 75) — analogue voltage from the upstream (pre-catalyst) oxygen sensor for closed-loop fuel trim
- Secondary O2 Sensor (pin 76) — analogue voltage from the downstream (post-catalyst) oxygen sensor for catalyst efficiency monitoring
- Engine Coolant Temperature Sensor (pin 83) — analogue voltage from the ECT sensor used for cold-start enrichment and fan control
- Throttle Position Sensor (pin 84) — analogue voltage proportional to throttle plate angle for load calculation and acceleration enrichment
- Vehicle Speed Sensor (pin 86) — speed pulse signal from the transmission for fuel cut and idle-up control
- Throttle Position Switch (pin 87) — discrete or analogue signal from the idle/WOT switch integrated with or adjacent to the throttle body
- Mass Air Flow (pin 90) — analogue voltage from the MAF sensor representing inducted air mass (turbo models)