# 1991-1996 Subaru Impreza ## Engine Turbocharged oposite 4 cylinder EJ20G ## Stock ECU A lot of useful info can be found at [ Diagnostics and Datalogging for Subaru SVX] ## ECU pinout This pinout can be partially correct for other Subaru from early 90s (with same yellow ECU connector). Like Legacy/Liberty, SVX and so on. ![Pinout](Images/Subaru_impreza_ecu_pinout_1991.png) Connector: Hardware:OEM_connectors#76_pin **EDM connector B44 (JDM - B60)** | Terminal | Type | EDM Signal | JDM Signal | Note | Wire color | | -------- | ------------------ | ------------------------------------ | ----------------------------------- | ---------------------------------------------------------------------- | ---------- | | 1 | OD output | Idle air control solenoid: close end | same | | | | 2 | OD output | Idle air control solenoid: open end | same | | | | 3 | OD output | Wastgate control solenoid | same | | | | 4 | OD output | Radiator fan 1 control | same | Ext relay | | | 5 | Open Emiter output | Self shutoff control | same | \+12 output to hold main relay on (serial diode protected on ECU side) | | | 6 | OD output | **Purge control solenoid valve** | **5th injector relay (RA-version)** | | | | 7 | OD+Pull-up output | Ignition control \#4 | same | | | | 8 | OD+Pull-up output | Ignition control \#3 | same | | | | 9 | OD+Pull-up output | Ignition control \#2 | same | | | | 10 | OD+Pull-up output | Ignition control \#1 | same | | | | 11 | OD output | Fuel injector \#3 | same | | | | 12 | OD output | Fuel injector \#2 | same | | | | 13 | OD output | Fuel injector \#1 | same | | | | 14 | Power | GND (power supply) | same | (not sure) | | | 15 | Power | Ignition GND | same | externaly connected to body | | | 16 | Input | Power steering pressure switch | same | to GND | | | 17 | OD output | Radiator fan 2 control | same | Ext relay | | | 18 | \- | No connection | same | | | | 19 | OD output | Jakie Chan lamp | same | | | | 20 | OD output | Pressure exchange solenoid valve | same | Used to switch pressure sensor between intake and atmosphere | | | 21 | \- | No connection | same | | | | 22 | OD output | AC cut relay | same | | | | 23 | OD output | Fuel pump relay | same | | | | 24 | Power | Injectors GND | same | | | | 25 | Power | Injectors GND | same | | | | 26 | OD output | Fuel injector \#4 | same | | | **EDM connector B96 (JDM B116)** | Terminal | Type | EDM Signal | JDM Signal | Note | Wire color | | -------- | --------- | ---------------------------------- | ----------- | ---------------------------------------------------------------------------- | ---------- | | 1 | Input | Camshaft position sensor: signal + | same | | | | 2 | Input | Camshaft position sensor: signal - | same | | | | 3 | Shield | Camshaft position sensor: shield | same | | | | 4 | Shield | Knock sensor: shield | same | | | | 5 | Input | Knock sensor: signal | same | | | | 6 | Input | Idle switch | ? | Throttle fully closed | | | 7 | Tx | Subaru Select Monitor signal | same | 5V uart, 1953 baud, 8 data bits, 1 stop bit, Even Parity and no flow control | | | 8 | Rx | Subaru Select Monitor signal | same | 5V uart, 1953 baud, 8 data bits, 1 stop bit, Even Parity and no flow control | | | 9 | Input | AC switch | same | to gnd | | | 10 | Input | Starter signal | same | | | | 11 | Input | ? | Idle switch | Throttle fully closed | | | 12 | Input | Read memory connector | same | connect to GND | | | 13 | Input | Test connector | same | connect to GND | | | 14 | \- | No connection | same | | | | 15 | \- | No connection | same | | | | 16 | Output 5V | Engine tachometer output | same | 2 pulses per rev | | **EDM connector B95 (JDM B115)** | Terminal | Type | EDM Signal | JDM Signal | Note | Wire color | | -------- | --------- | ------------------------------------ | ---------- | -------------------------------------- | ---------- | | 1 | Power OUT | Throttle position switch: GND/Shield | same | | | | 2 | Input | Throttle position switch: Signal | same | Fully closed: 4.7V, Fully opened: 0.9V | | | 3 | Power OUT | Throttle position switch: 5V | same | 5V output | | | 4 | Input | Crancshaft position sensor: signal + | same | | | | 5 | Input | Crancshaft position sensor: signal - | same | | | | 6 | Shield | Crancshaft position sensor: shield | same | | | | 7 | \- | No connection | same | | | | 8 | \- | No connection | same | | | | 9 | \- | No connection | same | | | | 10 | Input | Neutral switch | same | | | | 11 | Input | Vehicle speed | same | 5V level from dashboard | | | 12 | Input | IGN signal | same | | | **EDM connector B43 (JDM B59)** | Terminal | Type | EDM Signal | JDM Signal | Note | Wire color | | -------- | --------- | ------------------------------------ | -------------------- | ---------------------------- | ---------- | | 1 | \- | No connection | same | | | | 2 | Power | Power supply | same | Through main relay | | | 3 | Power OUT | Pressure sensor: 5V | same | 5V output | | | 4 | Input | Pressure sensor: signal | same | | | | 5 | Input | **No connection** | **EGT sensor input** | | | | 6 | Input | O2 sensor: signal | same | Rich: 0.7-1.0, Leam: 0.0-0.2 | | | 7 | Input | Engine coolant t | same | | | | 8 | Power OUT | MAF: 12V | same | | | | 9 | Input | MAF: signal | same | | | | 10 | Power OUT | MAF: GND | same | | | | 11 | Power | GND (control system) | same | | | | 12 | Output | **No connection** | **IP light ses (?)** | | | | 13 | Power | Power supply | same | Through main relay | | | 14 | \- | No connection | same | | | | 15 | Power | Back-up power supply | same | Always on | | | 16 | \- | No connection | same | | | | 17 | Input | O2 sensor: shield | same | | | | 18 | \- | No connection | same | | | | 19 | Power OUT | MAF: shield | same | | | | 20 | \- | No connection | same | | | | 21 | Power OUT | Pressure, coolant T, EGT sensors GND | same | | | | 22 | Power | GND (control system) | same | | | ## ECU connection Impreza 1991+ ![Wiring Diagram](Images/Subaru_impreza_ecu_connection_1991.png) Liberty RS 1993 ![Wiring Diagram](Images/92_liberty_rs_ecu.png) ## Stock ECU internals Output drivers: 4 x UPA1558H - 4 N-channel power MOSFETs 1 x 4AK19 - 4 N-channlel power MOSFETs (2.5 A) - seems to drive injectors (2S)A1441 - 5A PNP transistors - seems to drive self-shutdown control output ## See also [http://www.type-ra.com/](http://www.type-ra.com/)