General System Description

Closed Loop System Diagram:

The Electronic Control System is a computerized fuel, ignition and emission control system designed to maintain fuel economy, good driveability and reduced vehicle emissions. It supplies an optimum air/fuel ratio to the engine under a wide variety of operating conditions. An Electronic Control Module (ECM) monitors data from various sensors and controls functions such as injector pulse, ignition timing, turbocharger and emission control devices.

Fuel is metered to the intake system through a separate injector for each cylinder. Injectors are mounted on the intake manifold. Fuel pressure is held constant so that the amount of injector "ON" time calculated by the ECM from various sensors determines the amount of fuel injected.

To give an extra margin of safety in the event of system failure, the output of the ECM will automatically switch to fail-safe mode if a fault is detected in any of these components and/or systems:

Oxygen sensor
Coolant temperature sensor
Throttle position sensor
MAT sensor
MAP sensor
Vehicle speed sensor
Turbocharger wastegate control system
EGR system
EST system

If a malfunction develops in the micro computer within the control unit, the back-up control system will maintain the minimum necessary ECM functions to permit vehicle operation.

Components can be grouped as ECM input and output devices. Input devices control or produce voltage signals monitored by the ECM. Output devices are components controlled by the ECM.

INPUT DEVICES

Map sensor (codes 33 & 34)
Distributor-engine RPM (code 12)
Oxygen sensor (code 13)
Throttle position sensor (codes 21 & 22)
Coolant temperature sensor (codes 14 & 15)
MAT sensor (codes 23 & 25)
Knock (detonation) sensor (code 43)
Vehicle speed sensor (code 24)
Ignition switch
EGR gas temperature sensor (code 32)

OUTPUT DEVICES

Fuel injectors
Ignition timing control (code 42)
Knock (detonation) control of timing (code 43)
Idle speed control (IACV)
Fuel pump relay
"Check Engine" light
On-board diagnostics
EGR VSV (code 32)
AIR VSV
Canister purge VSV
Turbo wastegate control solenoid (code 31)
A/C clutch relay
Oxygen sensor lean (code 44)
Oxygen sensor rich (code 45)
Faulty or incorrect MEM-CAL (code 51)