System Description




Check Engine Warning Light

Check Connector


Ignition Coil w/lgniter

Start Switch (For A/T)

Pressure Regulator

CokJ Start

Throttle Position Sensor

Knock Sensor

Speed Sensor

Air Conditioner

The EFI used on Toyotas has three basic systems. FUEL SYSTEM

An electric fuel pump supplies sufficient fuel, under a constant pressure, to the EFI injectors. These injectors inject a metered quantity of fuel into the intake manifold in accordance with signals from the ECU. Each injector injects, at the same time, one half of the fuel required for ideal combustion with cach engine revolution.



The 5M-GE engine is equipped with a Toyota Computer Control System (TCCS) which centrally controls the EFI, ESA, EGR, Diagnosis systems, etc. by means of an Electronic Control Unit (ECU -formerly EFI computer) employing a microcomputer.

The air induction system provides sufficient air for engine operation.

EFI SYSTEM - System Description

By means of the ECU, the TCCS controls the following functions:

1. Electronic Fuel Injection (EFI)

The ECU receives signals from various sensors indicating changing engine operating conditions such as:

Intake air volume Intake air temperature Coolant temperature Engine rpm

Acceleration/deceleration Exhaust oxygen content etc.

These signals are utilized by the ECU to determine the injection duration necessary for an optimum air-fuel ratio.

2. Electronic Spark Advance (ESA)

The ECU is programmed with data for optimum ignition timing under any and all operating conditions. Using data provided by sensors which monitor various engine functions (rpm, intake air volume, coolant temperature, etc.), the microcomputer (ECU) triggers the spark at precisely the right instant. (See IG section)

3. Idle Speed Control (ISC)

The ECU is programmed with target engine speed values to respond to different engine conditions (coolant temperature, air conditioner ontoff, etc.). Sensors transmit signals to the ECU which controls the flow of air through the by-pass of the throttle valve and adjusts idle speed to the target value. (See pages Fl 43,60)

4. Exhaust Gas Recirculation (EGR)

The ECU detects the coolant temp, and controls EGR function accordingly. (See page EC-10)

5. Electronic Controlled Transmission (ECT) (Automatic Trans, only)

A serial signal is transmitted to the ECT computer to prevont shift up to 3rd or overdrive during cold engine operation. (See AT section)

6. Diagnostics

The ECU detects any malfunctions or abnor-malties in the sensor network and lights a "CHECK ENGINE" warning light on the instrument panel. At the seme time, the trouble is identified and a diagnostic code is recorded by the ECU. The diagnostic code can be read by the number of blinks of the "CHECK ENGINE" warning light when check connector are short-circuited. (See page FI-22)

7. Fail-Safe Function

In the event of a computer malfunction, a back-up circuit will take over to provide minimal drivability. Simultaneously, the "CHECK ENGINE" warning light is activated.

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