Evolution of Toyotas Electronic Fuel Injection Systems

Early Conventional EFI computers were first configured from analog circuits, and they controlled only fuel delivery and injection. The modem Electronic Control Units (ECU) utilize digital circuits and microprocessors which have served to improve EFI system capabilities.

Modern TCCS engine controls, introduced to the U.S.A. market in 1983, are capable of managing fuel delivery, idle speed control (ISC), electronic spark advance (ESA), and emissions systems with extraordinary speed and accuracy.

In the evolution of Toyota's fuel injection, three levels of electronic control refinements have taken place.

• Conventional EFI

The main difference between these systems is the capability of the ECU. These capabilities have grown from simple fuel control to the addition of self-diagnostics to the control of ignition spark advance and more. The following chart summarizes basic capabilities by system and can be used as a guide in identification and troubleshooting.

Evolution of Toyota EFI Systems

Fuel Control (EFI)

Spark Control (ESA)

Self Diagnosis

Fail Safe Strategy

Idle Speed Control (ISC)

Conventional EFI

YES

NO

NO

NO

NO

P7/EFI

YES

NO

YES

NO

NO

EFI/ TCCS

YES

YES

YES

YES

YES

System identification is relatively simple.

• The Conventional EFI system has no check engine light.

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