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Engine Control 2,0 l EFI Turbo, RS Cosworth (29)
Circuit Description
The electronic engine control system uses a network of sensors, switches, and solenoids and an Electronic Engine Control (EEC) module (A15) to control fuel flow, exhaust gas recirculation (EGR), ignition system functions, engine idle speed and the emissions system.
Voltage Supply
With the ignition off, voltage is present at pin 1 of the EEC module (A15) to protect the data stored in memory. With the ignition in run, all of the other components of the engine control system receive voltage. Pins 37 and 57 of the EEC module (A15) obtain current from fuse F3 with the ignition in run.
Ignition
The ignition system is controlled by the electronic Distributorless Ignition System (DIS) module (A23). The electronic DIS module (A23) controls two DIS ignition coils (T4, T5) and the crankshaft position sensor (B43) and is connected to pins 4, 36, and 56 of the EEC module (A15). The signal from pin 4 is used to detect intermittent ignition system faults. Pin 56 receives a profile ignition pickup (PIP) value which is used by the EEC module (A15) to determine crankshaft position. Pin 36 of the EEC module (A15) outputs a so-called SAW-signal (spark advance word) to the electronic DIS module (A23).
Fuel pump
The fuel pump relay (K4) receives voltage through the power hold relay (K13) and is controlled by pin 22 or pin 53 (for models as of MY 95) of the EEC module (A15). The current to pin 22 or pin 53 (for models as of MY 95) of the EEC module (A15) can be cut off by the inertia switch (N61), which shuts off the fuel pump in the fuel tank unit (A31) in case of an accident. Pin 8 of the EEC module (A15) is used as a fuel pump monitor input (only models before MY 95). The fuel pump runs constantly during normal operation, and the system pressure is preserved when the engine is shut off.
Power steering pressure switch (N96)
The power steering pressure switch (N96) sends a signal to pin 28 of the EEC module (A15) when the pressure is high. Under high power steering pressure, the EEC module (A15) increases the idle speed.
A/C Compressor Control
The A/C Wide Open Throttle (WOT) relay (K32) can be energised when pin 54 or pin 12 (for models as of MY 95) of the EEC module (A15) is connected to earth. This will cause the A/C compressor to be disengaged, thus reducing engine load.
Voltage is applied to pin 10 of the EEC module (A15) when the A/C system is turned on. This information is used to determine engine load and to control engine idle speed.
Diagnostic and Earth Connections
Pins 17 and 48 lead to the self test connector (D19).
Pins 18 and 19 lead to the data link connector (DLC) (D20).
For vehicles before MY 95, pin 29 leads to the service connector (D22).
Pins 16, 40, and 60 are connected to earth G1004 and pin 20 is connected to earth G1096.
Solenoids
The injector valve solenoids (Y9, Y10, Y11 and Y12) obtain their voltage from fuse F3 with the ignition in run. The EEC module (A15) (pins 58, 59, 39 and 35 only for models before MY 95) (pins 51, 52, 42 and 54 for models as of MY 95) controls the 4 injector valve solenoids continuously and individually. The injection quantity, that is, the duration of the input signal, is determined by the temperature, load and rpm of the engine as well as by the composition of the exhaust. The longer the pulse, the greater the amount of fuel that passes through the injector.
The idle speed control valve solenoid (Y13) obtains its distribution voltage from fuse F3. The EEC module (A15) compares the stored desired engine idle speed value with the actual engine idle speed and regulates the idle speed control valve solenoid (Y13) from pin 21. The idle speed control valve solenoid (Y13) varies the air volume into the engine via an auxiliary air passage.
The canister purge valve solenoid (Y1) is needed to open and close the activated carbon canister. When the valve is energised by connecting pin 11 of the EEC module (A15) to earth, the fuel vapours from the fuel tank can be drawn into the engine, mixed with the intake air and burned.
For vehicles before MY 95, the EVR (Exhaust gas recirculation Vacuum Regulator) valve solenoid (Y33) allows a measured quantity of exhaust gas to be directed back into the inlet manifold. The exhaust gas introduced into the inlet manifold dilutes the incoming mixture and reduces peak gas temperatures, thus reducing NOx emissions. The valve is vacuum operated and controlled by pin 33 of the EEC module (A15). The EGR system does not operate during conditions of over-run or wide open throttle.
The boost control valve (Y65) for the turbocharger is connected to pin 13 of the EEC module (A15).
Sensors
Pin 46 of the EEC module (A15) serves as earth for the Throttle Position Sensor (TPS) (B8), the Heated Exhaust Gas Oxygen (HEGO) sensor (B 59), the Engine Coolant Temperature (ECT) sensor (B10), the Air Charge Temperature (ACT) sensor (B 5), the Manifold Absolute Pressure (MAP) sensor (B 2) and for models before MY 95, the Exhaust Gas Recirculation (EGR) valve position sensor (B49).
The Throttle Position Sensor (TPS) (B
, the Manifold Absolute Pressure (MAP) sensor (B 2) and the Exhaust Gas Recirculation (EGR) valve postion sensor (B 49) receive a 5V reference from pin 26 of the EEC module (A15).
The Throttle Position Sensor (TPS) (B
consists of a potentiometer mounted on the throttle plate shaft that sends its signal to pin 47 of the EEC module (A15). Using this signal, the module can compute the position of the throttle valve (idle, partial load, or wide open) and use the input to calculate fuel delivery.
The Manifold Absolute Pressure (MAP) sensor (B 2) is a pressure-sensitive device which delivers electronic signals to pin 45 of the EEC module (A15). The frequency of the output signal changes with the intake manifold pressure. The EEC module (A15) uses this signal to adjust the air/fuel mixture and the ignition timing based on the current engine operating conditions.
The Exhaust Gas Recirculation (EGR) valve position sensor (B 49) measures the differential pressure in the feed exhaust and sends its signal to pin 27 of the EEC module (A15). The sensor is part of the EGR system.
The Heated Exhaust Gas Oxygen (HEGO) sensor (B 59) measures the amount of oxygen in the exhaust gases. A bounce signal is sent from the HEGO sensor (B 59) to pin 44 of the EEC module (A15) to determine if the air/fuel mixture should be richer or
leaner. This measurement is made so that the EEC module (A15) can maintain the air/fuel mixture composition close to the value of Lambda=1 for correct operation of the catalytic converter. Since the sensor does not function until it has reached its operating temperature, it contains a heating element to speed warm-up time. The heating element is turned off when pin 31 of the EEC module (A15) is connected internally to earth.
The Engine Coolant Temperature (ECT) sensor (B 10) (a temperature-dependent resistor) provides a voltage to pin 7 of the EEC module (A15). The sensor provides the EEC module (A15) with the engine operating temperature, needed to help calculate fuel delivery and ignition timing. The resistance of the sensor decreases with increasing temperature and increases with decreasing temperature.
The Air Charge Temperature (ACT) sensor (B 5) (a temperature-dependent resistor) provides a voltage to pin 25 of the EEC module (A15). The sensor provides the EEC module (A15) with a signal proportional to the temperature of the incoming air charge. The data is used to help calculate the opening times of the injector valves and the ignition timing.
The Vehicle Speed Sensor (VSS) (B 11) operates under the Hall effect principle and sends its signal continuously while the vehicle is moving to pin 3 of the EEC module (A15).
The crankshaft position sensor (B 43) provides pins 5 and 6 of the electronic DIS module (A23) with the position of the crankshaft. This data is used for correct timing of the injectors at engine start-up.
The camshaft position sensor (B 41) provides pin 24 of the EEC module (A15) with a reference point for the number 1 cylinder, which is necessary to ensure the correct sequence of injector opening.
The Mass Air Flow (MAF) sensor (B 22) measures the quantity of air passing into the engine via the air filter. The information is then fed back to pins 9 and 50 of the EEC module (A15) and is used to help calculate fuel delivery.
