Federal System Description

EFI System (Federal) (1 of 2):

EFI System (Federal) (2 of 2):

When any of such troubles, as listed below, occurs in the EFI system, the ECM stores the data on the defective area (where the trouble occurred) in its back-up memory. The memory is not erased when the ignition switch is turned "OFF" and it is retained until power to ECM is shut "OFF" for 20 seconds or longer. It indicates the defective area in memory by means of flashing the "CHECK ENGINE" light at the time of inspection (i.e. when diagnosis terminal is grounded and ignition switch is turned "ON").

A. When the ECM receives a defect informing signal from any one of the following sensors and circuits, or no signal.

- Oxygen sensor
- Manifold Air Temperature (MAT) sensor
- Manifold Absolute Pressure (MAP) sensor
- Coolant Temperature Sensor (CTS)
- Throttle Position Sensor (TPS)
- Idle switch circuit
- Lock-up circuit (For A/T vehicle)
- 5th switch circuit (For M/T vehicle)
- Ignition circuit

B. When the CPU (Central Processing Unit) of the ECM fails to operate.

"CHECK ENGINE" light:

The "CHECK ENGINE" light is located at the top of the instrument cluster. It indicates defective area identified by the self-diagnosis function of the ECM. It also lights when either of following conditions applies:

A. When the ignition switch is "ON" and engine is not running. When engine speed is lower than 500 rpm, the "CHECK ENGINE" light turns "ON" for the purpose of its circuit check, but turns "OFF" once the engine is started, (when engine speed is higher than 500 rpm) regardless of EFI system condition.

B. When the mileage reaches 50,000, 80,000 and 100,000 miles respectively (i.e. mileage sensor turns "ON") the "CHECK ENGINE" light turns "ON" even while engine is running. This is to warn the driver that it is time for a periodical maintenance inspection. In this case, turn "OFF" "CHECK ENGINE" light with its cancel switch upon completion of inspection. The cancel switch is located behind the access panel, below the steering column. To reset, slide the switch either left or right until the "CHECK ENGINE" light goes out.

FAIL-SAFE FUNCTION:

When a failure occurs, a signal indicating such failure is sent to the ECM, which judges that signal as such. However, control over the injector, ISC solenoid valve, and other components are maintained on the basis of the standard signals stored in the memory of the ECM, while ignoring that failure signal. This function is called "Fail-Safe Function." Thus, with this function, a certain level of engine performance is available even when some failures occur in these sensors or their circuits. This allows the vehicle to run even if a failure exist.

- Coolant Temperature Sensor (CTS)
- Throttle Position Sensor (TPS)
- Manifold Air Temperature (MAT) sensor
- Manifold Absolute Pressure (MAP) sensor

BACK-UP FUNCTION:

Even when the microcomputer in the ECM fails to operate properly, the back-up circuit in the ECM controls operation of the injector on the basis of the signals from the pressure sensor, so as to least impair driving performance.