Computers and Control Systems: Description and Operation

Fuel Injection System Schematic:

The Computerized Engine Controls (CEC) electronically regulate the air/fuel ratio, idle speed and ignition timing. This is done by two Electronic Control Units (ECU), one controlling the fuel injection system and the other controlling the ignition system.

FUEL INJECTION SYSTEM (BOSCH LH2.4-JETRONIC):

BOSCH LH2.4-JETRONIC stands for:

BOSCH = manufacturer
L = luft (German for air)
H = heiss (German for hot as in hot-wire)
2.4 = model series

This fuel injection is based on the Bosch multi-point fuel injection system with hot-wire air mass meter (LH-Jetronic). The ECU uses electrical input signals from various devices and sensors to calculate the engine load and condition. With this information it will adjust the injector frequency to provide optimal air/fuel mixture, performance, driveability and emissions output.

Input devices (the ECU receives):

^ Battery supply signal (voltage).
^ Ignition switch signal.
^ Oxygen sensor (lambda sond) signal.
^ Crankshaft speed signal from the ignition control unit.
^ Speedometer signal.
^ Crankshaft position signal from the ignition control unit.
^ Knock signal from the ignition control unit.
^ Coolant temperature signal.
^ Air mass meter signal.
^ Gear selector signal (automatic transmission only).
^ Throttle position signal.
^ A/C switch signal.
^ A/C pressure sensor signal.

Output devices (The ECU controls):

^ [1][2]System relay ground.
^ Suppressor relay by controlling the [1][2]system relay.
^ Fuel injector ground.
^ Cold start injector ground.
^ Idle air valve.
^ Air mass meter signal to the ignition system control unit (ignition ECU input device).
^ Shift indicator light (manual trans. only).
^ Diagnostic socket fault information.
^ "CHECK ENGINE" light.

If the self diagnostic circuit ("on board diagnostics") in the ECU detects a fault in the fuel injection system, it will activate the "CHECK ENGINE" light. By extracting the fault codes from the diagnostic socket, you can determine what component or components need further testing or replacement (see DIAGNOSIS AND TESTING PROCEDURES). Federal and Canada market vehicles can store up to three fault codes, California market vehicles can store up to 15 fault codes.

Ignition System Schematic:

IGNITION SYSTEM (BOSCH EZ116K):

BOSCH EZ116K stands for:

BOSCH = manufacturer
E = elektronische (German for electronic)
Z = zuendung (German for ignition)
116 = model series
K = klopfregelung (German for knock control)

This ignition is based on the fully electronically controlled Bosch ignition system with knock control (EZ-K). The ECU uses electrical input signals from various devices and sensors to calculate the engine load and condition. With this information the ECU will adjust the ignition timing to provide optimal performance, driveability and emissions output.

Input devices (the ECU receives):

^ Battery supply signal (voltage).
^ Ignition switch signal.
^ Crankshaft position and speed signal.
^ Knock signal.
^ Coolant temperature signal.
^ Air mass meter signal from fuel injection control unit.
^ Throttle position signal.
^ EGR temperature sensor signal (Calif. only).

Output devices (The ECU controls):

^ Power stage.
^ Crankshaft speed (RPM) signal to the fuel injection control unit (fuel injection ECU input device).
^ Crankshaft position signal to the fuel injection control unit (fuel injection ECU input device).
^ Knock signal to the fuel injection control unit (fuel injection ECU input device).
^ Diagnostic socket fault information.
^ EGR converter ground.
^ "CHECK ENGINE" light.
^ EGR converter (Calif. only).

If the self diagnostic circuit ("on board diagnostics") in the ECU detects a fault in the ignition system, it will activate the "CHECK ENGINE" light. By extracting the fault codes from the diagnostic socket, you can determine what component or components need further testing or replacement (see DIAGNOSIS AND TESTING PROCEDURES). The system can store up to three fault codes.