Файл: 92FWD_14.pdf

Fig. 16 Canister Purge Solenoid

Fig. 17 Electric EGR Transducer

INSTALLATION

(1)Connect vacuum hoses.

(2)Connect electrical connector.

Fig. 18 Engine Controller

Fig. 19 Heated Oxygen Sensor

(1) Disconnect oxygen sensor electrical connector (Fig. 20).

GENERAL INFORMATION

The turbocharged multi-point electronic fuel injection system combines an electronic fuel and spark advance control system with a turbocharged intake system (Fig. 1). The fuel injection system is controlled by the Single Board Engine Controller II (SBEC II), referred to in this manual as the engine controller.

The engine controller regulates ignition timing, airfuel ratio, emission control devices, cooling fan, charging system, speed control, turbocharger wastegate and idle speed. The engine controller adapts its requirement to meet changing operating conditions.

Various sensors provide the inputs necessary for the engine controller to correctly regulate fuel flow at the fuel injector. These include the manifold absolute pressure, throttle position, oxygen sensor, coolant temperature, detonation, and vehicle distance sensors. In addition to the sensors, various switches and relays provide important information and system control. The inputs include the park/neutral switch and air conditioning clutch switch. The outputs include the auto shutdown relay and fuel pump relay.

All inputs to the engine controller are converted into signals. Based on these inputs the engine controller adjusts air-fuel ratio, ignition timing, turbocharger wastegate and other controlled outputs. The

engine controller adjusts the air-fuel ratio by changing injector pulse width. Injector pulse width is the time an injector is energized.

SYSTEM DIAGNOSIS

The engine controller tests many of its own input and output circuits. If a fault is found in a major system, the information is stored in memory. Technicians can display fault information through the instrument panel Check Engine lamp or by connecting the Diagnostic Readout Box II (DRB II). For fault code information, refer to On Board Diagnostics in 2.5L Turbo I Multi-Point Fuel InjectionÐGeneral Diagnosis section of this group.

CCD BUS

Various controllers and modules exchange information through a communications port called the CCD Bus. The engine controller transmits vehicle load data on the CCD Bus.

ENGINE CONTROLLER

The engine controller is a digital computer containing a microprocessor (Fig. 2). The controller receives input signals from various switches and sensors that are referred to as Engine Controller Inputs. Based on these inputs, the controller adjusts various engine

and vehicle operations through devices that are referred to as Engine Controller Outputs.

Fig. 2 Engine Controller

Engine Controller Inputs:

²Air Conditioning Controls

²Battery Voltage

²Brake Switch

²Coolant Temperature Sensor

²Detonation (Knock) Sensor

²Distributor (Hall Effect) Pick-up

²Manifold Absolute Pressure (MAP) Sensor

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²Oxygen Sensor

²SCI Receive

²Speed Control System Controls

²Throttle Position Sensor

²Park/Neutral Switch (automatic transmission)

²Vehicle Distance (Speed) Sensor

Engine Controller Outputs:

²Air Conditioning Clutch Relay

²Alternator Field

²Automatic Idle Speed (AIS) Motor

²Auto Shutdown (ASD) Relay

²Barometric Read Solenoid

²Canister Purge Solenoid

²Check Engine Lamp

²Diagnostic Connector

²Fuel Injector

²Ignition Coil

²Part Throttle Unlock Solenoid (Automatic Transmission)

²Radiator Fan Relay

²Speed Control Solenoids

²Tachometer Output

²Wastegate Solenoid

Based on inputs it receives, the engine controller adjusts fuel injector pulse width, idle speed, ignition spark advance, ignition coil dwell and canister purge operation. The engine controller regulates operation of the cooling fan, A/C and speed control systems. The controller changes alternator charge rate by adjusting the alternator field.

The engine controller adjusts injector pulse width (air-fuel ratio) based on the following inputs.

²battery voltage

²coolant temperature

²detonation sensor

²exhaust gas content

²engine speed (distributor pick-up)

²manifold absolute pressure

²throttle position

The engine controller adjusts ignition timing based on the following inputs.

²coolant temperature

²engine speed (distributor pick-up)

²manifold absolute pressure

²throttle position

The auto shutdown (ASD) and fuel pump relays are mounted externally. The engine controller turns both relays on and off through the same circuit.

The distributor pick-up signal is sent to the engine controller. If the engine controller does not receive a distributor signal within approximately one second of engine cranking, the ASD relay and fuel pump relay are deactivated. When these relays are deactivated, power is shut off from the fuel injector, fuel pump, ignition coil, and oxygen sensor heater element.

The engine controller contains a voltage converter that changes battery voltage to a regulated 9.0 volts

FUEL SYSTEMS 14 - 49

to power the distributor pick-up and vehicle speed sensor. The controller also provides a 5.0 volts supply for the coolant temperature sensor, manifold absolute pressure sensor and throttle position sensor.

AIR CONDITIONING SWITCH SENSEÐENGINE CONTROLLER INPUT

When the air conditioning or defrost switch is put in the ON position and the low pressure and high pressure switches are closed, the engine controller receives an input indicating that the air conditioning has been selected. After receiving this input, the engine controller activates the A/C compressor clutch by grounding the A/C clutch relay. The engine controller also adjusts idle speed to a scheduled RPM to compensate for increased engine load.

BATTERY VOLTAGEÐENGINE CONTROLLER INPUT

The engine controller monitors the battery voltage input to determine fuel injector pulse width and alternator field control.

If battery voltage is low the engine controller will increase injector pulse width (period of time that the injector is energized).

BRAKE SWITCHÐENGINE CONTROLLER INPUT

When the brake switch is activated, the engine controller receives an input indicating that the brakes are being applied. After receiving the input, the controller vents the speed control servo. Venting the servo turns the speed control system off.

COOLANT TEMPERATURE SENSORÐENGINE CONTROLLER INPUT

The coolant temperature sensor is installed behind the thermostat housing and ignition coil in the hot box. The engine controller supplies 5 volts to the coolant temperature sensor. The sensor provides an input voltage to the engine controller (Fig. 3). As coolant temperature varies, the coolant temperature sensor resistance changes resulting in a different input voltage to the engine controller.

The engine controller demands slightly richer airfuel mixtures and higher idle speeds until the engine reaches normal operating temperature.

This sensor is also used for cooling fan control.

DETONATION SENSOR (KNOCK SENSOR)ÐENGINE CONTROLLER INPUT

The detonation sensor generates a signal when spark knock occurs in the combustion chambers. The sensor is mounted on the intake manifold (Fig. 4). The sensor provides information used by the engine controller to modify spark advance and boost schedules in order to eliminate detonation.

14 - 50 FUEL SYSTEMS

Fig. 3 Coolant Temperature Sensor

Fig. 4 Detonation Sensor

DISTRIBUTOR (HALL EFFECT) PICK-UPÐENGINE CONTROLLER INPUT

The distributor pick-up supplies engine speed to the engine controller. The distributor pick-up is a Hall Effect device (Fig. 5).

A shutter (sometimes referred to as an interrupter) is attached to the distributor shaft. The shutter contains four blades, one per engine cylinder. A switch plate is mounted to the distributor housing above the shutter. The switch plate contains the distributor pick-up (a Hall Effect device and magnet) through which the shutter blades rotate. As the shutter blades pass through the pick-up, they interrupt the magnetic field. The Hall effect device in the pick-up senses the change in the magnetic field and switches on and off (which creates pulses), generating the input signal to

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Fig. 5 Distributor Pick-UpÐTypical

the engine controller. The engine controller calculates engine speed through the number of pulses generated.

One of the shutter blades has a window cut into it. The window tells the engine controller which injector to energize. Also, the controller uses the input for control of detonation.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSORÐENGINE CONTROLLER INPUT

The engine controller supplies 5 volts to the MAP sensor. The MAP sensor converts intake manifold pressure into voltage. The engine controller monitors the MAP sensor output voltage. As vacuum increases, MAP sensor voltage decreases proportionately. Also, as vacuum decreases, MAP sensor voltage increases proportionately.

During cranking, before the engine starts running, the engine controller determines atmospheric air pressure from the MAP sensor voltage. While the engine operates, the controller determines intake manifold pressure from the MAP sensor voltage.

Based on MAP sensor voltage and inputs from other sensors, the engine controller adjusts spark advance and the air/fuel mixture.

The MAP sensor mounts on the dash panel inside the engine compartment (Fig. 6). A vacuum hose connects the sensor to the throttle body.

OXYGEN SENSOR (O2 SENSOR)ÐENGINE CONTROLLER INPUT

The O2 sensor is located in the exhaust manifold and provides an input voltage to the engine controller (Fig. 7). The input tells the engine controller the oxygen content of the exhaust gas. The engine con-

Fig. 6 Manifold Absolute Pressure (MAP) Sensor

Location

troller uses this information to fine tune the air-fuel ratio by adjusting injector pulse width.

system to enter into closed loop operation sooner. Also, it allows the system to remain in closed loop operation during periods of extended idle.

In Closed Loop operation the engine controller monitors the O2 sensor input (along with other inputs) and adjusts the injector pulse width accordingly. During Open Loop operation the engine controller ignores the O2 sensor input. The controller and adjusts injector pulse width based on a preprogrammed (fixed) oxygen sensor input value and inputs from other sensor.

SPEED CONTROLÐENGINE CONTROLLER INPUT

The speed control system provides four separate voltages (inputs) to the engine controller. The voltages correspond to the On/Off, Set, and Resume.

The speed control ON voltage informs the engine controller that the speed control system has been activated. The speed control SET voltage informs the controller that a fixed vehicle speed has been selected. The speed control RESUME voltage indicates the previous fixed speed is requested. The speed control OFF voltage tells the controller that the speed control system has deactivated. Refer to Group 8H for further speed control information.

TRANSMISSION PARK/NEUTRAL SWITCHÐENGINE CONTROLLER INPUT

The park/neutral switch is located on automatic transmission housing (Fig. 8). Manual transmission do not use park/neutral switches. The switch provides an input to the engine controller. The input indicates if the automatic transmission is in Park, Neutral, or a drive gear selection. The input is used to determine idle speed (varying with gear selection), fuel injector pulse width, and ignition timing advance. The park neutral switch is sometimes referred to as the neutral safety switch.

Fig. 7 Oxygen Sensor

The O2 sensor produces voltages from 0 to 1 volt, depending upon the oxygen content of the exhaust gas in the exhaust manifold. When a large amount of oxygen is present (caused by a lean air-fuel mixture), the sensor produces a low voltage. When there is a lesser amount present (rich air-fuel mixture) it produces a higher voltage. By monitoring the oxygen content and converting it to electrical voltage, the sensor acts as a rich-lean switch.

The oxygen sensor is equipped with a heating element that keeps the sensor at proper operating temperature during all operating modes. Maintaining correct sensor temperature at all times allows the

Fig. 8 Park Neutral Switch

THROTTLE POSITION SENSOR (TPS)ÐENGINE CONTROLLER INPUT

The Throttle Position Sensor (TPS) is mounted on the throttle body and connected to the throttle blade shaft (Fig. 9). The TPS is a variable resistor. The sensor provides the engine controller with an input