Federal Models

Engine Management System Schematic:

PURPOSE
The Bosch LH/EZL Computerized Engine Control system electronically regulates the air/fuel mixture, idle speed, and ignition timing to achieve optimum engine performance. Optimum performance means the best possible compromise between the demands of high power, low fuel consumption, and the cleanest possible exhaust emissions.

CONSTRUCTION
The system uses three interconnected Electronic Control modules (ECM's); one controlling the fuel injection system, one controlling the ignition system and one controlling the electronic accelerator system.

All three systems feature self-diagnostics and fault code storage. All fault codes are accessed through the 38-pole diagnostic socket (X11/4).

SELF-DIAGNOSTICS
The self-diagnostic system is a built-in function of the ECM's. Each ECM constantly monitors engine performance by comparing its programming "window" with the values it receives from various sensors. When a programming parameter has been exceeded, a retrievable fault code is stored.

The self diagnostic circuit ("on board diagnostics") in the ECM can be accessed for troubleshooting purposes. By extracting the fault codes using the diagnostic socket (X11/4), you can determine what component or components need further testing or replacement.

FUEL INJECTION SYSTEM (BOSCH LH):
The LH fuel injection system is based on the Bosch multi-point fuel injection system with mass air flow sensor (LH-Jetronic). The ECM uses electrical input signals from various devices and sensors to calculate the engine load and condition. With this information it adjusts the injection duration and timing to provide the optimum air/fuel mixture for performance, driveability, and emissions compliance.

ADAPTIVE MEMORY
Time and mileage affect the operation of both the injection and the idle control systems. To compensate for wear and deposit accumulation, the LH system modifies its basic programming (within a "window" of operation) to provide efficient operation under all driving conditions. If the system determines that it must modify its basic programming beyond the "window", a fault code is stored in the self-diagnostic memory.

LIMP HOME OPERATION
If the ECM determines that the mass air flow signal is incorrect, the system enters a pre-set "limp home" function. In "limp home" mode, a pre-set injection duration allows the vehicle to be driven to the nearest garage.

IGNITION SYSTEM (BOSCH EZL/AKR):
The EZL ignition system is based on the electronically controlled Bosch ignition system with knock control (EZL/AKR). The ECM uses electrical input signals from various devices and sensors to calculate the engine temperature, load and speed. With this information the ECM adjusts the ignition timing to provide optimum performance, economy, and emissions output.

ELECTRONIC ACCELERATOR SYSTEM:
This engine control system is equipped with an electronically controlled accelerator pedal/throttle plate. The electronic accelerator ECM (N4/1) controls the idle speed. This system keeps the engine in a constant RPM range when at idle. The system will compensate for cold engine, high engine load or other influencing factors.