Engine Control Module: Description and Operation
The Engine Control Module (ECM) uses the signal from the ignition switch to detect when the ignition key has been turned to position II or III. When
the key is in the ignition position (position II) or starting position (position III) a high signal (Ubat) is transmitted from the ignition switch to the engine
control module (ECM). The engine management system prepares for start-up (for example, temporarily activates the fuel pump (FP) relay). When the
flywheel in the engine rotates, the engine speed (RPM) sensor signal is used to keep the fuel pump (FP) relay activated.
The fuse in the fusebox in the passenger compartment supplies current to the ignition switch.
The central electronic module (CEM) can diagnose the ignition switch.
See Design and Function, Immobilizer.
Fuel pump control module (only vehicles with demand controlled fuel pumps)
The fuel pump control module powers the fuel pump and regulates the output of the pump. The fuel pressure changes with the output of the pump.
The fuel pump control module is supplied with battery voltage by the fuel pump (FP) relay and is grounded in the car body. The fuel pump (FP) relay is
controlled by the central electronic module (CEM) when requested by the engine control module (ECM).
The engine cannot be started if the power supply to the fuel pump control module is faulty because the fuel pump will not then be powered.
The fuel pump control module is controlled by the engine control module (ECM) via serial communication. The fuel pump control module then controls
the fuel pump by transmitting a PWM voltage on the ground lead for the fuel pump. This means that the voltage drop across the pump changes, and with
it the output of the fuel pump. Also see Function See: Powertrain Management/Computers and Control Systems/Description and Operation/Bosch
ME7.01 Engine Management System/Function.
There are no diagnostics for the fuel pump control module. The engine control module (ECM) has diagnostics for fuel pressure regulation and the
associated components. Also see Fuel pressure regulation, diagnostics See: Powertrain Management/Computers and Control Systems/Description and
Operation/Fuel Pressure Regulation, Diagnostics.