Toyota Cressida and Van 1983-1990

Description and Operation


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Fig. Fig. 1 Schematic of the Electronic Fuel Injection system and components-1983-84 Van

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Fig. Fig. 2 Schematic of the Electronic Fuel Injection system and components-1985-89 Van

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Fig. Fig. 3 Schematic of the Electronic Fuel Injection system and components-1983-84 Cressida

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Fig. Fig. 4 Schematic of the Electronic Fuel Injection system and components-1985-88 Cressida

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Fig. Fig. 5 Schematic of the Electronic Fuel Injection system and components-1989-90 Cressida

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 EFI computer. Each injector injects at the same time, one half of the fuel required for ideal combustion with each engine revolution. The air induction system provides sufficient air for the engine operation.

The engines are equipped with a Toyota Computer Control System (TCCS) which centrally controls the electronic fuel injection, electronic spark advance and the exhaust gas recirculation valve. The systems can be diagnosed by means of an Electronic Control Unit (ECU) which employs a microcomputer. The ECU and the TCCS control the following functions:


Electronic Fuel Injection (EFI)

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

Intake air volume
Intake air temperature
Coolant temperature sensor
Engine rpm
Exhaust oxygen content

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

Electronic Spark Advance (ESA)

The ECU is programmed with data for optimum ignition timing during any and all operating conditions. Using the 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 moment.

Idle Speed Control (ISC)

The ECU is programmed with specific engine speed values to respond to different engine conditions (coolant temperature, air conditioner on/off, etc.). Sensors transmit signals to the ECU which controls the flow of air through the by-pass of the throttle valve and adjusts the idle speed to the specified value.

Exhaust Gas Recirculation (EGR)

The ECU detects the coolant temperature and controls the EGR operations accordingly.

Electronic Controlled Transmission (ECT)

This unit only applies to automatic transmissions.

A serial signal is transmitted to the ECT computer to prevent shift up to third or overdrive during cold engine operation. Diagnostics, which are outlined below.

Fail-Safe Function

In the event of a computer malfunction, a backup circuit will take over to provide minimal driveability. Simultaneously, the CHECK ENGINE warning light is activated.


Do not operate the fuel pump when the fuel lines are empty
Do not reuse fuel hose clamps
Make sure all EFI harness connectors are fastened securely. A poor connection can cause an extremely high surge voltage in the coil and condenser and result in damage to integrated circuits
Keep the EFI harness at least 4 in. (100mm) away from adjacent harnesses to prevent an EFI system malfunction due to external electronic "noise"
Keep EFI parts and harnesses dry during service
Before attempting to remove any parts, turn OFF the ignition switch and disconnect the battery ground cable
Always use a 12 volt battery as a power source
Do not attempt to disconnect the battery cables with the engine running
Do not depress the accelerator pedal when starting
Do not rev up the engine immediately after starting or just prior to shutdown
Do not attempt to disassemble the EFI control unit under any circumstances
If installing a two-way or CB radio, keep the antenna as far as possible away from the electronic control unit. Keep the antenna feeder line at least 8 in. (200mm) away from the EFI harness and do not let the two run parallel for a long distance. Be sure to ground the radio to the vehicle body
Do not apply battery power directly to injectors
Handle air flow meter carefully to avoid damage
Do not disassemble air flow meter or clean meter with any type of detergent


Before connecting or disconnecting the control unit ECU harness connectors, make sure the ignition switch is OFF and the negative battery cable is disconnected to avoid the possibility of damage to the control unit
When performing ECU input/output signal diagnosis, remove the pin terminal retainer from the connectors to make it easier to insert tester probes into the connector
When attaching or disconnecting pin connectors from the ECU, take care not to bend or break any pin terminals. Check that there are no bends or breaks on ECU pin terminals before attempting any connections
Before replacing any ECU, perform the ECU input/output signal diagnosis to make sure the ECU is functioning properly
After checking through EFI troubleshooting, perform the EFI self-diagnosis and driving test
When measuring supply voltage of ECU controlled components with a circuit tester, separate one tester probe from another. If the two tester probes accidentally make contact with each other during measurement, a short circuit will result and damage the power transistor in the ECU