General Information

The Toyota Computer Control System (TCCS) is used on 1983-88 5M-GE engines, 1985-88 4A-GE, 4A-GEC, 4A-GEL, 4A-GELC, 22R-E and 22R-TE engines, 1986 2SE, 1986-88 3S-GE and 4Y-EC engines, late 1986 7M-GE engines, 1987-88 3S-FE, 7M-GE and 7M-GTE engines.

The system uses a micro-processor control unit (ECU) to electronically control fuel injection, ignition timing, engine idle speed and exhaust gas recirculation. The ECU monitors engine and vehicle operating conditions through a group of sensors and controls fuel delivery, ignition advance and EGR based on these signals in order to provide optimum engine performance while reducing exhaust emissions. In addition, the ECU contains self-diagnostic circuitry which allows it to detect sensor circuit malfunctions, alert the operator to malfunctions, and allow the technician to easily locate defective components.
If the ECU detects malfunctions or abnormalities in the system/sensor circuit, a ``Check Engine'' lamp on the instrument panel will illuminate. When the ECU detects and signals a system malfunction, the trouble is identified and stored in the ECU memory as a diagnostic code. The diagnostic codes, including one signaling ``normal'' operation can be accessed and identified using standard test equipment. In addition, the computer contains a back-up circuit which allows minimal vehicle operation in the case of ECU malfunction. This condition is known as Fail-Safe.
If an ECU failure should occur, the TCCS system will operate on a back-up circuit that provides minimum driveability. The ``Check Engine'' warning lamp will also be illuminated.