General System Description

Control Module
The Motronic 4.4 is an electronic engine management system which controls:

^ Fuel injection
^ Ignition
^ Idling speed
^ Engine cooling fan (FC)
^ EVAP system
^ Air conditioning (A/C) system
^ Pulsed secondary air injection system

The engine control module (ECM) incorporates a microprocessor which receives signals from the various sensors in the car. This micro-processor uses a program to compute the necessary engine management functions.

The ECM incorporates adaptive functions, which enable it to adjust its computations continuously to suit running conditions and when cold starting.

By managing the engine effectively exhaust gas emissions can be kept low. CO content and idling speed do not need to be adjusted. The need for servicing is small.

The ECM also has an on-board diagnostics system. Signals from sensors, and the operation of the three-way catalytic converter (TWC) and EVAP system are continuously monitored. If possible the ECM will adopt fixed substitute values (limp-home values) to enable the car to be driven if certain signals are faulty or missing.

Substitute values can be adopted for:

- engine coolant temperature (ECT) sensor
- throttle position (TP) sensor
- heated oxygen sensors (HO2S)
- camshaft position (CMP) sensor
- mass air flow (MAF) sensor.

Faults are recorded in the ECM memory. Information can be read off using the Volvo Scan Tool (ST) connected to the data link connector (DLC) in the center console.

The control module is located by the left A-pillar (LHD) or right A-pillar (RHD) behind the panel.





Input Signals
The engine control module (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 angle, 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 (7/82)
^ engine knock (if present), from the two knock sensors (KS) (7/23 and 7/24)
^ vehicle speed, from the combined instrument panel (5/1) imminent gear shifting, from the automatic transmission control module (TCM) (4/28) (automatics only)
^ gear selector lever in park/neutral or drive positions, from the automatic transmission control module (4/28)
^ malfunction indicator lamp (MIL) request from the automatic transmission control module (4/28)
^ vertical acceleration of the car from accelerometer (7/79) to determine if the car is being driven on an uneven road, misfire diagnostic
^ air conditioning (A/C) (3/54) compressor request from pressure switch (Pressostat) (7/53)
^ pressure in air conditioning system, from the air conditioning pressure sensor (7/8)





Control Functions
The engine control module (ECM) controls the following components and functions on the basis of these input signals:

^ main relay (2/32)
^ fuel pump (FP), by activating the fuel pump relay (2/23)
^ fuel injection, by individually activating injectors (8/6-8/11)
^ ignition, by transmitting signals to ignition discharge modules (4/38 and 4/39)
^ idling speed, by operating the idle air control (IAC) valve (8/5)
^ pressure in the inlet manifold during engine braking by regulating the idle air control valve (8/5)
^ engine cooling fan (FC), by activating the fan control relay (2/11)
^ EVAP-system canister purge (CP) valve (8/18)
^ malfunction indicator lamp (MIL) (10/93) for emission related faults
^ preheating of front and rear heated oxygen sensors (HO2S) (7/15 and 7/82)
^ air conditioning (A/C) compressor relay (2/22), for activating and shutting-off the compressor
^ pulsed secondary air injection system solenoid valve (8/43)
^ pulsed secondary air injection system pump, by activating the pulsed secondary air injection system pump relay (2/53).





Other Output Signals
The engine control module (ECM) also transmits signals to the following components:

^ confirmation of torque limiting by ignition retardation, to the automatic transmission control module (TCM) (4/28)
^ engine speed and load signals to the automatic transmission control module (4/28)
^ throttle angle signal to the automatic transmission control module (4/28)
^ engine speed (RPM) signal to the combined instrument panel tachometer (5/1)
^ engine coolant temperature (ECT) signal to the combined instrument panel (5/1).