14 - 52 FUEL SYSTEMS
signal (voltage) representing throttle blade position. As the position of the throttle blade changes, the resistance of the TPS changes.
Fig. 9 Throttle Position Sensor (TPS) and Automatic
Idle Speed Motor (AIS)
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 engine controller receives an input signal voltage from the TPS varying in an approximate range of from 1 volt at minimum throttle opening (idle) to 4 volts at wide open throttle. Along with inputs from other sensors, the engine controller uses the TPS input to determine current engine operating conditions. The engine controller adjusts fuel injector pulse width and ignition timing based on these inputs.
Ä
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 (A/C) 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.
With the engine operating, the engine controller cycles the air conditioning clutch on and off when the A/C switch closes with the blower motor switch in the on position. When the engine controller senses low idle speeds or wide open throttle through the throttle position sensor, it de-energizes the A/C clutch relay. The relay contacts open, preventing air conditioning clutch engagement.
On AG and AJ models, the A/C clutch relay is located in the power distribution center. Refer to the Wiring and Component Identification section of Group 8W.
ON AA and AP models, the A/C clutch relay is mounted to the inner fender panel, next to the drivers side strut tower (Fig. 11).
VEHICLE DISTANCE (SPEED) SENSORÐENGINE CONTROLLER INPUT
The distance sensor (Fig. 10) is located in the transmission extension housing. The sensor input is used by the engine controller to determine vehicle speed and distance traveled.
Fig. 10 Vehicle Distance (Speed) Sensor |
|
The distance sensor generates 8 pulses per sensor |
Fig. 11 Relay Identification |
revolution. These signals, along with a closed throttle |
|
signal from the TPS, determine if a closed throttle |
|
deceleration or normal idle condition (vehicle stopped) |
|
Ä
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.
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 engine controller monitors the distributor pick-up signal to determine engine speed and ignition timing (coil dwell). If the controller does not receive a distributor signal when the ignition switch is in the Run position, it de-energizes both relays. Battery voltage is not supplied to the fuel injector, ignition coil, fuel pump and oxygen sensor heating element.
On AG and AJ models, the ASD relay and fuel pump relay are located in the power distribution center. Refer to the Wiring and Component Identification section of Group 8W.
On AA and AP models, the ASD relay and fuel pump relay are mounted on the drivers side fender well, next to the strut tower (Fig. 11).
AUTOMATIC IDLE SPEED (AIS) MOTORÐENGINE CONTROLLER OUTPUT
The idle speed stepper motor is mounted on the throttle body and is controlled by the engine controller (Fig. 9). The engine controller adjusts engine idle speed through the AIS motor 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 from the throttle position sensor, speed sensor (distributor pick-up coil), coolant temperature sensor, and various switch operations (brake, park/neutral, air conditioning). Deceleration die out is also prevented by increasing airflow when the throttle is closed quickly after a driving (speed) condition.
FUEL SYSTEMS 14 - 53
BAROMETRIC READ SOLENOIDÐENGINE CONTROLLER OUTPUT
The barometric pressure read solenoid is tied into the manifold absolute pressure (MAP) sensor vacuum hose (Fig. 6). 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 specified RPM band. Barometric information is used primarily for boost control.
CANISTER PURGE SOLENOIDÐENGINE CONTROLLER OUTPUT
Vacuum for the Evaporative Canister is controlled by the Canister Purge Solenoid (Fig. 12). The solenoid is controlled by the engine controller.
Fig. 12 Canister Purge Solenoid and Wastegate
Control Solenoid
The engine controller operates the solenoid by switching the ground circuit on and off. When energized, the solenoid 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 controller grounds the purge solenoid. When the solenoid energizes, 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.
14 - 54 FUEL SYSTEMS
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 incorrect 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 to display any fault codes stored in the controller. Refer to On Board Diagnostics in the General DiagnosisÐ2.5L Turbo I 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.
Ä
Fig. 13 Fuel Injector
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 an input from the distributor pick-up. Refer to Auto Shutdown (ASD) Relay/Fuel Pump RelayÐEngine Controller Output in this section for relay operation.
The ignition coil is mounted on the hot box next to the thermostat housing (Fig. 14).
FUEL INJECTORÐENGINE CONTROLLER OUTPUT
The Fuel Injectors are electric solenoids driven by the engine controller (Fig. 13).
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 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 |
Fig. 14 Ignition Coil |
||
The engine controller provides a |
ground contact |
||
|
|||
(circuit) for energizing the ignition |
coil. When the |
|
|
Ä
PART THROTTLE UNLOCK SOLENOIDÐENGINE CONTROLLER OUTPUT
Three-speed automatic transaxles use a part throttle unlock solenoid. The engine controller controls the lock-up of the torque convertor through the part throttle unlock solenoid. The transmission is locked up only in direct drive mode. Refer to Group 21 for transmission information.
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 and AJ models, the radiator fan relay is located in the power distribution center. Refer to the Wiring and Component Identification section of Group 8W.
On AA and AP models, the radiator fan relay is mounted on the drivers side fender well, next to the strut tower (Fig. 11).
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. 12).
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.
FUEL SYSTEMS 14 - 55
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. The input indicates if the calculated injector pulse width results in an 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 2.5L Turbo I multi point fuel injection system has the following modes of operation:
²Ignition switch ON - Zero RPM
²Engine start-up
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).
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 a distributor signal it energizes the auto shutdown (ASD) relay and fuel pump relay. These relays supply battery voltage to the fuel injector, ignition coil and oxygen sensor heating element. If the engine controller does not receive a distributor input, it de-energizes the ASD and fuel pump relays after approximately one second.
14 - 56 FUEL SYSTEMS
With the engine idling within 664 RPM of the target RPM, the controller compares the current MAP value with the atmospheric pressure value it received during the Ignition Switch On (Zero RPM) Mode. If a minimum difference between the two is not detected, a MAP sensor fault is set into memory.
Once the ASD relay and fuel pump relay have energized, the engine controller:
²Supplies a ground path to each injector. The injectors are pulsed four times per engine revolution instead of the normal two pulses per revolution.
²Determines injector pulse width based on coolant temperature, MAP sensor input, throttle position, and the number of engine revolutions since cranking was initiated.
²Monitors the coolant temperature sensor, distributor pick-up, MAP sensor, and throttle position sensor to determine correct ignition timing.
ENGINE WARM-UP MODE
This is a OPEN LOOP mode. The following inputs are received by the engine controller:
²coolant temperature
²detonation sensor
²manifold absolute pressure (MAP)
²engine speed (distributor pick-up)
²throttle position
²A/C switch
²battery voltage
The engine controller provides a ground path for the injectors to precisely control injector pulse width (by switching the ground on and off). The engine controller regulates engine idle speed by adjusting the automatic idle speed motor. Also, the controller adjusts ignition timing.
When the engine is at operating temperature, this is a CLOSED LOOP mode. During cruising speed the following inputs are received by the engine controller:
²coolant temperature
²detonation sensor
²manifold absolute pressure
²engine speed
²throttle position
²exhaust gas oxygen content
²A/C control positions
²battery voltage
The engine controller provides a ground path for the injectors to precisely control injector pulse width. The engine controller controls engine idle speed and ignition timing. The engine controller controls the air/fuel ratio according to the oxygen content in the exhaust gas.
Ä
This is a CLOSED LOOP mode. The engine controller recognizes an abrupt increase in throttle position or MAP pressure as a demand for increased engine output and vehicle acceleration. The engine controller increases injector pulse width in response to increased fuel demand.
This is a CLOSED LOOP mode. During deceleration the following inputs are received by the engine controller:
²coolant temperature
²detonation sensor
²manifold absolute pressure
²engine speed
²throttle position
²exhaust gas oxygen content
²A/C control positions
²battery voltage
The engine controller may receive a closed throttle input from the throttle position sensor (TPS) at the same time it senses an abrupt decrease in manifold pressure from the manifold absolute pressure (MAP) sensor. This indicates a hard deceleration. The engine controller may modify the injector firing sequence. Modifying the injector firing sequence helps maintain better control of the air-fuel mixture (as sensed through the O2 sensor).
This is an OPEN LOOP mode. During wide open throttle operation, the following inputs are received by the engine controller:
²coolant temperature
²detonation sensor
²manifold absolute pressure
²engine speed
²throttle position
When the controller senses a wide open throttle condition, it de-energizes the air conditioning clutch relay. This disables the air conditioning system.
The exhaust gas oxygen content input is not accepted by the engine controller during wide open throttle operation. The engine controller will enrichen the air/fuel ratio to increase performance and compensate for increased combustion chamber temperature.
This is an OPEN LOOP mode. When the ignition switch is turned to the OFF position, the following occurs:
²All outputs are turned off.
²No inputs are monitored.
²The engine controller shuts down.