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 first-generation Mitsubishi Eclipse (D27A/D29A chassis, 1989–1994) was built under the Diamond-Star Motors joint venture between Mitsubishi Motors and Chrysler at the Normal, Illinois plant. It shared its platform — and its ECU connector pinout — with the Eagle Talon and Plymouth Laser of the same generation. The turbocharged 4G63 2.0 L DOHC engine uses a single large ECU connector carrying 76 pins on the turbo models, governing multi-point injection, ignition timing, boost control, and sensor inputs. Non-turbo variants use the 4G15 or 4G37 engine with a reduced pin count.
| Pin | name | Signal |
|---|---|---|
| 4 | Primary O2 Sensor | Analog |
| 8 | Intake Air Temperature Sensor | Analog |
| 18 | Vehicle Speed Sensor | Speed |
| 19 | Throttle Position Sensor | Analog |
| 20 | Engine Coolant Temperature Sensor | Analog |
| 55 | Ignition Control Module | RPM |
| 101 | Power Ground | Ground |
Signals
- Primary O2 Sensor — narrowband oxygen sensor signal used by the ECU for closed-loop fuel trim
- Intake Air Temperature Sensor — thermistor input measuring inlet air temperature for fuel and ignition correction
- Vehicle Speed Sensor — pulse signal from the transmission providing road speed to the ECU
- Throttle Position Sensor — potentiometer input indicating throttle plate angle for load calculation
- Engine Coolant Temperature Sensor — thermistor input used for cold-start enrichment, cooling fan control, and ignition advance
- Ignition Control Module — tachometric signal from the igniter/power transistor unit; represents engine RPM
- Power Ground — chassis ground reference for ECU power supply
Notes
The ECU uses a single multi-pin connector on 4G63 turbo-equipped models. The connector body and pin assignments are identical across the 1G Diamond-Star Motors platform (Eclipse, Eagle Talon, Plymouth Laser). Only a partial subset of pin functions is documented here; the full 76-pin assignment is detailed in the Diamond-Star Motors factory service documentation.