System Overview

System overview

Control module




The engine control module (ECM) controls the following functions:
- start
- injectors
- ignition
- fuel pressure
- throttle
- camshafts (CVVT)
- evaporative emission system (EVAP) valve
- engine cooling fan (FC)
- Air conditioning (A/C) compressor
- alternator control module (ACM) (2005-).
The engine control module (ECM) is supplied with battery voltage (Ubat) via fuses in the central electronic module (CEM) and in the integrated relay/fusebox in the engine compartment.
To prevent certain stored date from being erased from the engine control module (ECM) when the ignition is switched off, the control module also has a 30-supply. This supply is from the integrated relay/fusebox in the engine compartment.
The control module is grounded via the wiring which is connected at the right-hand suspension turret.
The engine control module (ECM) contains a voltage regulator which maintains a low voltage (5 V) in internal components in the control module such as:
- Analog/Digital converter
- Digital/Analog converter
- Micro-processor.
The functions which require battery power (Ubat) and high output are controlled by external or internal power stages. For example ignition coils have external power stages (integrated into the ignition coils) while the power stages for the injectors are integrated into the control module.
The micro-processor in the engine control module (ECM) receives signals from the different sensors and control modules in the vehicle. The micro-processor uses a program which calculates how the signals from the different sensors and other control modules are to be interpreted and how the components / functions need to be controlled.
The control module has several self-learning (adaptive) functions. It continually adapts ongoing calculations to changing circumstances (wear, air leaks, differences between different fuels).
Emissions are kept low through efficient management of the injection period, ignition, evaporative emission system (EVAP) valve and camshafts etc. Faults which affect emissions can be detected by running diagnostics for functions and components.
The engine control module (ECM) is in the intake system. It is cooled by the engine intake air.
The engine control module (ECM) communicates with other control modules using controller area network (CAN) communication.
The engine control module (ECM) checks activations, input and output signals and functions using an integrated diagnostic system. A diagnostic trouble code (DTC) is stored if, after validation, the control module detects a fault. In certain cases the faulty signal is also replaced with a substitute value or certain functions are limited.

For example, substitute values can be set for:
- engine coolant temperature (ECT) sensor
- mass air flow (MAF) sensor
- throttle position (TP) sensor
- air pressure
- fuel pressure.
Mathematical calculations and signals from certain components are used to calculate the substitute values. Other substitute values are fixed, predefined values in the control module.
The substitute value allows the car to be driven and for the emissions to be kept at a reasonable level even though vital functions/components are malfunctioning.

Functions which may be limited are for example:
- Camshaft control (CVVT)
- fuel trim
- throttle angle
- fuel pressure regulation.
The substitute values are used and functions restricted so that the system is still able to work whilst protecting components that are required for safety reasons (for example the throttle angle).
Any diagnostic trouble codes (DTCs) are stored in the control module memory. This information can be read off using VIDA via the data link connector (DLC) in the vehicle.

Signals
The table below summarizes the input signals to and output signals from the Engine Control Module (ECM). The signal types are divided into directly connected signals, serial communication and controller area network (CAN) communication. The illustration below displays the same information with the Volvo component designations.