Файл: 92FWD_14.pdf

Fig. 12 MAP Sensor

OXYGEN SENSOR (O2 SENSOR)ÐENGINE CONTROLLER INPUT

The O2 sensor is located in the turbocharger outlet and provides an input voltage to the engine controller (Fig. 13). The input tells the engine controller the oxygen content of the exhaust gas. The engine controller uses this information to fine tune the air-fuel ratio by adjusting injector pulse width.

Fig. 13 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 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 adjusts injector pulse width based on preprogrammed (fixed) values and inputs from other sensors.

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.

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. 14). The TPS is a variable resistor that provides the engine controller with an input signal (voltage) representing throttle blade position. As the position of the throttle blade changes, the resistance of the TPS changes.

Fig. 14 Throttle Position Sensor and AIS Motor

The engine controller supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the engine controller) represents the throttle blade position. The TPS output voltage to the controller varies from approximately 0.5 volt at minimum throttle opening (idle) to 4 volts at wide open

Fig. 15 Vehicle Distance (Speed) Sensor

The distance sensor generates 8 pulses per sensor revolution. These signals, along with a closed throttle signal from the TPS, determine if a closed throttle deceleration or normal idle condition (vehicle stopped) exists. Under deceleration conditions, the engine controller adjusts the AIS motor to maintain a desired MAP value. Under idle conditions, the engine controller adjusts the AIS motor to maintain a desired engine speed.

AIR CONDITIONING CLUTCH RELAYÐENGINE CONTROLLER OUTPUT

The engine controller operates the air conditioning clutch relay ground circuit. The radiator fan relay supplies battery power to the solenoid side of the A/C clutch relay. The air conditioning clutch relay will not energize unless the radiator fan relay energizes. The engine controller energizes the radiator fan relay when the air conditioning or defrost switch is put in the ON position and the low pressure and high pressure switches close. When the engine controller senses wide open throttle through the throttle position sensor, or low engine RPM it will de-energize the A/C clutch relay, open it's contacts and prevent air conditioning clutch engagement.

On AA body vehicles, the relay is located on the drivers side inner fender panel (Fig. 16). On AG Body vehicles, the relay is located in the power distribution center (Fig. 17).

Fig. 16 Relay LocationÐAA Body

Fig. 17 Relay LocationÐAG Body

ALTERNATOR FIELDÐENGINE CONTROLLER OUTPUT

The engine controller regulates the charging system voltage within a range of 12.9 to 15.0 volts. Refer to Group 8A for charging system information.

AUTO SHUTDOWN (ASD) RELAY AND FUEL PUMP RELAYÐENGINE CONTROLLER OUTPUT

The engine controller operates the auto shutdown (ASD) relay and fuel pump relay through one ground path. The controller operates the relays by switching the ground path on and off. Both relays turn on and off at the same time.

Ä

The ASD relay connects battery voltage to the fuel injector and ignition coil. The fuel pump relay connects battery voltage to the fuel pump and oxygen sensor heating element.

The engine controller turns the ground path off when the ignition switch is in the Off position. Both relays are off. When the ignition switch is in the On or Crank position, the controller monitors the crankshaft and camshaft sensor signals to determine engine speed and ignition timing (coil dwell). If the engine controller does not receive the crankshaft and camshaft signals when the ignition switch is in the Run position, it will de-energize both relays. When the relays are de-energized, battery voltage is not supplied to the fuel injector, ignition coil, fuel pump and oxygen sensor heating element.

On AA body vehicles, the ASD relay and fuel pump relay are mounted on the drivers side fender well (Fig. 16).

On AG body vehicles, the ASD relay and fuel pump relay are located in the power distribution center (Fig. 17).

AUTOMATIC IDLE SPEED (AIS) MOTORÐENGINE CONTROLLER OUTPUT

The idle speed stepper (AIS) motor is mounted on the throttle body (Fig. 14). The engine controller operates the AIS motor. The engine controller adjusts engine idle speed through the AIS to compensate for engine load or ambient conditions.

The throttle body has an air bypass passage that provides air for the engine at idle (the throttle blade is closed). The AIS motor pintle protrudes into the air bypass passage and regulates air flow through it.

The engine controller adjusts engine idle speed by moving the AIS motor pintle in and out of the bypass passage. The adjustments are based on inputs the controller receives. The inputs are from the throttle position sensor, camshaft sensor, crankshaft sensor, coolant temperature sensor, and various switch operations (brake and air conditioning). Deceleration die out is also prevented by increasing airflow when the throttle is closed quickly after a driving (speed) condition.

BAROMETRIC READ SOLENOIDÐENGINE CONTROLLER OUTPUT

The barometric pressure read solenoid is spliced into the manifold absolute pressure (MAP) sensor vacuum hose (Fig. 12). The barometric read solenoid switches the pressure supply to the MAP sensor from either barometric pressure (atmospheric) or manifold vacuum. The engine controller operates the solenoid.

Atmospheric pressure is periodically supplied to the MAP sensor to measure barometric pressure. This occurs at closed throttle, once per throttle closure but no more often than once every 3 minutes and within a

FUEL SYSTEMS 14 - 83

specified RPM band. Barometric information is used primarily for boost control and start fuel enrichment at various altitudes.

CANISTER PURGE SOLENOIDÐENGINE CONTROLLER OUTPUT

Vacuum for the Evaporative Canister is controlled by the Canister Purge Solenoid (Fig. 18). The solenoid is controlled by the engine controller.

Fig. 18 Canister Purge Solenoid and Wastegate

Control Solenoid

The engine controller operates the solenoid by switching the ground circuit on and off. When grounded, the solenoid energizes and prevents vacuum from reaching the evaporative canister. When not energized the solenoid allows vacuum to flow to the canister.

During warm-up and for a specified time period after hot starts the engine controller grounds the purge solenoid. Vacuum does not operate the evaporative canister valve.

The engine controller removes the ground to the solenoid when the engine reaches a specified temperature and the time delay interval has occurred. When the solenoid is de-energized, vacuum flows to the canister purge valve. Vapors are purged from the canister and flow to the throttle body.

The purge solenoid will also be energized during certain idle conditions, in order to update the fuel delivery calibration.

CHECK ENGINE LAMPÐENGINE CONTROLLER OUTPUT

The Check Engine Lamp comes on each time the ignition key is turned ON and stays on for 3 seconds as a bulb test. The Check Engine Lamp warns the operator that the engine controller has entered a Limp-in mode. During Limp-in-Mode, the controller attempts to keep the system operational. The check engine lamp signals the need for immediate service. In limp-in mode, the Engine controller compensates for the failure of certain components that send incor-

14 - 84 FUEL SYSTEMS

rect signals. The controller substitutes for the incorrect signals with inputs from other sensors.

Signals that can trigger the Check Engine Lamp.

²Coolant Temperature Sensor

²Manifold Absolute Pressure Sensor

²Throttle Position Sensor

²Battery Voltage Input

²An Emissions Related System

²Charging system

The Check Engine Lamp can also be used to display fault codes. Cycle the ignition switch on, off, on, off, on, within five seconds and any fault codes stored in the Engine controller will be displayed. Refer to On Board Diagnostics in the General DiagnosisÐ2.2L Turbo III Engines section of this Group for Fault Code Descriptions.

DIAGNOSTIC CONNECTORÐENGINE CONTROLLER OUTPUT

The diagnostic connector provides the technician with the means to connect the DRB II tester to diagnosis the vehicle.

FUEL INJECTORÐENGINE CONTROLLER OUTPUT

The Fuel Injectors are electric solenoids driven by the engine controller (Fig. 19).

Ä

sharp edge of the injector nozzle. The resulting fuel sprays forms a cone shaped pattern before entering the air stream.

Fuel is constantly supplied to the injector at regulated 380 Kpa (55 psi). Unused fuel returns to the fuel tank.

IGNITION COILÐENGINE CONTROLLER OUTPUT

The Direct Ignition System (DIS) uses a molded coil (Fig. 20). The coil is mounted on the front of the engine. High tension leads route to each cylinder from the coil. The coil fires two spark plugs every power stroke. One plug is the cylinder under compression, the other cylinder fires on the exhaust stroke. The engine controller determines which of the coils to charge and fire at the correct time.

Fig. 19 Fuel Injector

Based on sensor inputs, the engine controller determines when and how long the fuel injector should operate. The amount of time an injector fires is referred to as injector pulse width. The auto shutdown (ASD) relay supplies battery voltage to the injector. The engine controller supplies the ground path. By switching the ground path on and off, the engine controller adjusts injector pulse width.

When the controller supplies a ground path, a spring loaded needle or armature lifts from its seat. Fuel flows through the orifice and deflects off the

Fig. 20 Ignition Coil

The auto shutdown (ASD) relay provides battery voltage to the ignition coil. The engine controller provides a ground contact (circuit) for energizing the coil. When the controller breaks the contact, the energy in the coil primary transfers to the secondary causing the spark. The engine controller will de-energize the ASD relay if it does not receive the crankshaft sensor and camshaft sensor inputs. Refer to Auto Shutdown (ASD) Relay/Fuel Pump RelayÐEngine Controller Output in this section for relay operation.

RADIATOR FAN RELAYÐENGINE CONTROLLER OUTPUT

The radiator fan is energized by the engine controller through the radiator fan relay. The engine controller grounds the radiator fan relay when engine coolant reaches a predetermined temperature. For more information, refer to Group 7, Cooling Systems.

On AG body vehicles, the radiator fan relay is located in the power distribution center (Fig. 17). Refer to the Wiring and Component Identification section of Group 8W.

Ä

On AA body vehicles, the radiator fan relay is mounted on the drivers side fender well, next to the strut tower (Fig. 16).

SPEED CONTROL SOLENOIDSÐENGINE CONTROLLER OUTPUT

The speed control vacuum and vent solenoids are operated by the engine controller. When the engine controller supplies a ground to the vacuum solenoid, the speed control system opens the throttle plate. When the controller supplies a ground to the vent solenoid, throttle blade closes. The engine controller balances the two solenoids to maintain the set speed. Refer to Group 8H for speed control information.

TACHOMETERÐENGINE CONTROLLER OUTPUT

The engine controller supplies engine RPM to the instrument panel tachometer. Refer to Group 8 for tachometer information.

WASTEGATE CONTROL SOLENOIDÐENGINE CONTROLLER OUTPUT

The engine controller operates the wastegate control solenoid. The controller adjusts maximum boost to varying engine conditions by changing the amount of time the solenoid is energized. The solenoid mounts to the passenger side inner fender panel, next to the strut tower (Fig. 18).

MODES OF OPERATION

As input signals to the engine controller change, the engine controller adjusts its response to the output devices. For example, the engine controller must calculate a different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT). There are several different modes of operation that determine how the engine controller responds to the various input signals.

There are two different areas of operation, OPEN LOOP and CLOSED LOOP.

During OPEN LOOP modes, the engine controller receives input signals and responds according to preset engine controller programming. Input from the oxygen (O2) sensor is not monitored during OPEN LOOP modes.

During CLOSED LOOP modes, the engine controller does monitor the oxygen (O2) sensor input. This input indicates to the engine controller whether or not the calculated injector pulse width results in the ideal air-fuel ratio of 14.7 parts air to 1 part fuel. By monitoring the exhaust oxygen content through the O2 sensor, the engine controller can fine tune the injector pulse width to achieve optimum fuel economy combined with low emissions.

The 2.2L Turbo III multi-point fuel injection system has the following modes of operation:

²Ignition switch ON - Zero RPM

²Engine start-up

FUEL SYSTEMS 14 - 85

²Engine warm-up

²Cruise (Idle)

²Acceleration

²Deceleration

²Wide Open Throttle

²Ignition switch OFF

The engine start-up (crank), engine warm-up, and wide open throttle modes are OPEN LOOP modes. The acceleration, deceleration, and cruise modes, with the engine at operating temperature are CLOSED LOOP modes (under most operating conditions).

IGNITION SWITCH ON (ZERO RPM) MODE

When the ignition switch activates the fuel injection system the following actions occur:

²The engine controller calculates basic fuel strategy by determining atmospheric air pressure from the MAP sensor input.

²The engine controller monitors the coolant temperature sensor and throttle position sensor input. The engine controller modifies fuel strategy based on this input.

When the key is in the ON position and the engine is not running, the auto shutdown (ASD) relay and fuel pump relay are not energized. Therefore battery voltage is not supplied to the fuel pump, ignition coil, fuel injector or oxygen sensor heating element.

ENGINE START-UP MODE

This is an OPEN LOOP mode. The following actions occur when the starter motor is engaged.

If the engine controller receives the camshaft and crankshaft signals, it energizes the auto shutdown (ASD) relay and fuel pump relay. These relays supply battery voltage to the fuel pump, fuel injectors, ignition coil, and oxygen sensor heating element. If the engine controller does not receive the camshaft and crankshaft signals within approximately one second, it de-energizes the ASD relay and fuel pump relay.

The engine controller energizes all injectors until it determines crankshaft position from the camshaft and crankshaft signals. The controller determines crankshaft position within 1 engine revolution.

After determining crankshaft position, the controller begins energizing the injectors in sequence. The controller adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and Off.

When the engine idles within 664 RPM of its target RPM, the controller compares current MAP sensor value with the atmospheric pressure value received during the Ignition Switch On (zero RPM) mode. If the controller does not detect a minimum difference between the two values, it sets a MAP fault into memory.