Toyota 1993 MR2, Wiring Diagrams

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2. CONTROL SYSTEM
* SMPI (EFI, ELECTRONIC FUEL INJECTION) SYSTEM
THE SMPI (EFI) SYSTEM MONITORS THE ENGINE REVOLUTIONS THROUGH THE SIGNALS EACH SENSOR (INPUT SIGNALS (1) TO
(12)) INPUTS TO THE PCME (ECU). BASED ON THIS DATA AND THE PROGRAM MEMORIZED IN THE PCME (ECU), THE MOST
APPROPRIATE FUEL INJECTION TIMING IS DECIDED AND CURRENT IS OUTPUT TO TERMINALS #1, #2, #3 AND #4 OF THE PCME
(ECU), CAUSING THE INJECTORS TO OPERATE IT (TO INJECT FUEL). IT IS THIS SYSTEM WHICH, THROUGH THE WORK OF THE
PCME (ECU), FINELY CONTROLS FUEL INJECTION IN RESPONSE TO DRIVING CONDITIONS.
* EI (ESA, ELECTRONIC SPARK ADVANCE) SYSTEM
THE EI (ESA) SYSTEM MONITORS THE ENGINE REVOLUTIONS USING THE SIGNALS (INPUT SIGNALS (1, 2, 4, 5, 6, 9, 11, 12)) INPUT
TO THE PCME (ECU) FROM EACH SENSOR. BASED ON THIS DATA AND THE PROGRAM MEMORIZED IN THE PCME (ECU), THE
MOST APPROPRIATE IGNITION TIMING IS DECIDED AND CURRENT IS OUTPUT TO TERMINAL IGT OF THE PCME (ECU). THIS
OUTPUT CONTROLS THE IGNITER TO PRODUCE THE MOST APPROPRIATE IGNITION TIMING FOR THE DRIVING CONDITIONS.
* FUEL PUMP CONTROL SYSTEM
THE PCME (ECU) OPERATION OUTPUTS TO TERMINAL FPR AND CONTROLS THE FUEL PUMP RELAY AND THUS CONTROLS THE
FUEL PUMP DRIVE SPEED IN RESPONSE TO CONDITIONS.
* HOZS (OXYGEN SENSOR) HEATER CONTROL SYSTEM
THE HOZS (OXYGEN SENSOR) HEATER CONTROL SYSTEM TURNS THE HEATER TO ON WHEN THE INTAKE AIR VOLUME IS LOW
(TEMP. OF EXHAUST EMISSIONS LOW), AND WARMS UP THE HOZS (OXYGEN SENSOR) TO IMPROVE DETECTION PERFORMANCE
OF THE SENSOR. THE PCME (ECU) EVALUATES THE SIGNALS FROM EACH SENSOR (INPUT SIGNALS (1, 4, 8, 9, 11)), CURRENT IS
OUTPUT TO TERMINAL HT AND CONTROLS THE HEATER.
* ISC (IDLE SPEED CONTROL) SYSTEM
THE ISC SYSTEM (ROTARY SOLENOID TYPE) INCREASES ENGINE SPEED AND PROVIDES IDLING STABILITY FOR FAST IDLE–UP
WHEN THE ENGINE IS COLD AND WHEN THE IDLE SPEED HAS DROPPED DUE TO ELECTRICAL LOAD, ETC. THE PCME (ECU)
EVALUATES THE SIGNALS FROM EACH SENSOR (INPUT SIGNALS 1, 4 TO 9, 13)), OUTPUTS CURRENT TO TERMINALS RSC AND
RSO AND CONTROLS THE IACV (ISC VALVE).
* EGR CONTROL SYSTEM
WITH THE EGR CONTROL SYSTEM, THE PCME (ECU) EVALUATES THE (INPUT SIGNALS (1, 4, 5, 9)) FROM EACH SENSOR,
CURRENT IS OUTPUT TO TERMINAL EGR AND OPERATION OF THE VSV (FOR EGR) IS CONTROLLED.
* INTAKE AIR CONTROL SYSTEM
IN THE INTAKE AIR CONTROL SYSTEM, EACH CYLINDER IN THE INTAKE MANIFOLD IS DIVIDED INTO TWO PARTS, WITH AN INTAKE
AIR CONTROL VALVE INSTALLED IN THE PASSAGE ON ONE SIDE. THE OPENING AND CLOSING OF THE VALVE PROVIDES THE
MOST APPROPRIATE INTAKE AIR FLOW AND, AS WELL AS PREVENTING PERFORMANCE LOSS AT LOW SPEEDS, ALSO IMPROVES
FUEL ECONOMY. THE PCME (ECU) EVALUATES THE SIGNALS FROM EACH SENSOR (INPUT SIGNALS (4, 5, 9, 12)), OUTPUTS
CURRENT TO TERMINAL TVIS CONTROLS THE VSV (FOR T–VIS) AND, CARRIES OUT OPENING AND CLOSING OF THE VALVE.
3. DIAGNOSIS SYSTEM
WITH THE DIAGNOSIS SYSTEM, WHEN THERE IS A MALFUNCTION IN THE PCME (ECU) SIGNAL SYSTEM, THE MALFUNCTIONING
SYSTEM IS RECORDED IN THE MEMORY. THE MALFUNCTIONING SYSTEM CAN THEN BE FOUND BY READING THE DISPLAY
(CODE) OF THE CHECK ENGINE WARNING LIGHT.
4. FAIL–SAFE SYSTEM
WHEN A MALFUNCTION OCCURS IN ANY SYSTEM, IF THERE IS A POSSIBILITY OF ENGINE TROUBLE BEING CAUSED BY
CONTINUED CONTROL BASED ON THE SIGNALS FROM THAT SYSTEM. THE FAIL–SAFE SYSTEM EITHER CONTROLS THE SYSTEM
BY USING DATA (STANDARD VALUES) RECORDED IN THE PCME (ECU) MEMORY OR ELSE STOPS THE ENGINE.