Motronic Multiport Fuel Injection System Overview

SYSTEM OVERVIEW





Engine Control Module
Motronic 4.3 SFI/DI is an electronic fuel injection/ignition management system whose main functions are to control the following:

^ Fuel injection
^ Ignition
^ Idling speed
^ Turbocharger (TC) boost pressure (only turbo)
^ Engine cooling fan
^ EGR system
^ EVAP system

The Engine Control Module (ECM) incorporates a microprocessor which receives signals from various sensors in the car. The microprocessor uses a program to compute necessary engine management functions.

The ECM incorporates 'self-learning' (adaptive) functions, which enable it to adjust its computations continuously to suit running conditions.

Efficient engine management ensures that exhaust gas emissions can be maintained at a low level. Since the CO content and idling speed do not require adjustment, the service requirement is minimal.

The ECM also incorporates an On-Board Diagnostic (OBD) function. Signals from the system sensors are constantly monitored, as are Three-Way Converter (TWC) function, the EVAP system and EGR system. If certain signals are lost or become faulty, the ECM will adopt fixed substitute values ("limp-home" values) to enable the car to be driven.

Substitute values can be adopted for functions such as the:

- Engine Coolant Temperature (ECT) Sensor signal
- Throttle Position (TP) Sensor signal
- Mass Air Flow (MAF) Sensor signal

Faults are recorded in the ECM memory in the form of Diagnostic Trouble Codes (DTCs). The relevant information may be displayed in the following manners:

^ Using the LED on the Volvo Data Link Connector (DLC) in the engine compartment to display the DTCs
^ Using the Volvo Diagnostic Key ST connected to the DLC
^ Using the Volvo System Tester, Scan Tool (ST) connected to the DLC
^ Using a Generic Scantool (GST) connected to the OBD II DLC in the center console in front of the gear lever (certain markets only)

The ECM is housed in a box in the engine compartment.

Input Signals:

Input Signals
The ECM receives signals describing running conditions from the following components:

^ Engine speed and crankshaft position, from the Engine Speed (RPM) Sensor at the flywheel (7/25)
^ Working cycle in cylinders, from the Camshaft Position (CMP) Sensor (7/21)
^ Engine load, from the Mass Air Flow (MAF) Sensor (7/17)
^ Engine temperature, from the Engine Coolant Temperature (ECT) Sensor (7/16)
^ Throttle opening, from the Throttle Position (TP) sensor (7/54)
^ Oxygen content of the exhaust gases upstream of the catalytic converter, from the front Heated Oxygen Sensor (HO2S) (7/15)
^ Oxygen content of the exhaust gases downstream of the catalytic converter, from the rear Heated Oxygen Sensor (HO2S) (7/82) (certain markets only)
^ Engine knock (if present), from the two Knock Sensors (KS) (7/23 and 7/24)
^ Vehicle speed, from the combined instrument (5/1)
^ Imminent gear-change, from the automatic Transmission Control Module (TCM) (4/28) (automatics only)
^ If the gear selector on automatic cars is in the P or N position or in Drive, from the automatic TCM (4/28)
^ Request to operate the Malfunction Indicator Lamp (MIL) from the TCM (4/28)
^ EGR system temperature from the EGR temperature sensor (7/37), for control of EGR system operation (certain markets only)
^ Vertical acceleration of the car from Acceleration Sensor (7/79) to determine if the car is being driven on an uneven road, misfiring diagnosis (certain markets only)
^ From the A/C system control panel (3/54), if A/C is selected
^ A/C compressor 'on' signal, from the Pressostat (7/53)
^ Pressure in the A/C high-pressure circuit, from the A/C Pressure Sensor (7/50)

Control Functions:

Control Functions
The ECM controls the following components and functions in response to the input signals:

^ Main relay (2/32)
^ Fuel pump, by activating the fuel pump relay (2/23)
^ Fuel injection, by operating the injectors (8/6-8/10) individually
^ Ignition, by transmiffing signals to the power stage integral with the ignition coil (4/44)
^ Idling speed, by operating the Idle Air Control (IAC) Valve (8/5)
^ Pressure in the intake manifold during engine braking by regulating the Idle Air Control (IAC) Valve (8/5)
^ Turbocharger (TC) boost pressure, by transmitting signals to the turbo charger (TC) control valve (8/28) (only turbo)
^ Engine cooling fan, by activating the Fan Control (FC) relay (2/11)
^ EVAP valve (8/18)
^ EGR vacuum controller (8/17)
^ MIL (10/106) in the case of faults which alter the exhaust emission levels
^ Heating of front and rear HO2S (7/15 and 7/82)
^ A/C compressor relay (2/22), to switch off the compressor

Other Output Signals
The ECM also transmits signals to the following components:

^ Acknowledgement of torque reduction by timing retardation, to the TCM (4/28)
^ Engine speed and load signals to the TCM (4/28)
^ Throttle opening signal to the TOM (4/28)
^ Engine speed (RPM) signal to the combined instrument tachometer (5/1)
^ Engine coolant temperature (ECT) signal to the combined instrument temperature gauge (5/1)
^ Injected fuel quantity to the combined instrument trip computer (5/4)