Engine Controls (Introduction) -- 3.5L (L66): Other Saturn VUE I

Temperature vs Resistance - Engine Coolant Temperature (ECT) Sensor

Temperature vs Resistance - Engine Coolant Temperature (ECT) Sensor

Temperature vs Resistance - Intake Air Temperature (IAT) Sensor

Temperature vs Resistance - Intake Air Temperature (IAT) Sensor

Idle Learn Procedure

1. Install a scan tool.
2. Diagnose and repair any DTCs before proceeding with this procedure. Refer to «Diagnostic Trouble Code (DTC) List»(ref-188783-S39578934162005090200000) for the applicable DTC that set.
3. Ensure that all electrical loads and accessories are OFF.
4. Turn OFF the air conditioning.
5. Ensure that the vehicle is in PARK or NEUTRAL.
6. Turn ON the ignition.
7. Clear the DTC information with the scan tool.
8. Wait 5 seconds and start the engine.
9. Operate the engine with no load at 3,000 RPM until the ECT reaches 90°C (194°F).
10. Let the engine idle with the THROTTLE CLOSED and the engine cooling fan OFF, for a total of 5 minutes.
11. The PCM has a new learned idle position.
12. The idle learn procedure is required when the following service procedures have been performed: The throttle body assembly is replaced The throttle valve is cleaned-Deposits can build up in the throttle body requiring periodic cleaning of the throttle valve and throttle bore area. Refer to «Throttle Body Service»(ref-188786-S11328555002005090200000) . The Clear DTCs function has been performed The PCM has been programmed. The PCM is replaced

Tools Required

J 39194-C Oxygen Sensor Wrench

J 39194-C Oxygen Sensor Wrench

J 39194-C Oxygen Sensor Wrench

J 39194-C Oxygen Sensor Wrench

Throttle Body Service

1. Remove the throttle body from the vehicle. Refer to «Throttle Body Assembly Replacement»(ref-188786-S38084220082005090200000) .
2. Open the throttle valve (3) of the throttle body (2).
3. Use a solvent soaked cloth (1) to remove dirt or carbon deposits/buildup from the throttle valve and the throttle bore.
4. Ensure that the throttle valve and throttle bore are clean and dry.
5. Inspect that the throttle valve operates smoothly and freely. Install the throttle body to the vehicle. Refer to «Throttle Body Assembly Replacement»(ref-188786-S38084220082005090200000) .
6. Reset the TP Learned Value. Refer to «Scan Tool Output Controls»(ref-188783-S04773074012005090200000) .
7. Perform the Idle Learn Procedure. Refer to «Idle Learn Procedure»(ref-188786-S26252071172005090200000) .

SA9127E Gage Bar Set

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(ref-188769-S19455074222005090200000) in Engine Electrical.
2. Connect the SA9127E to the fuel pressure connection. Refer to «Fuel Pressure Gage Installation and Removal»(ref-188786-S02796227162005090200000) .
3. Install the bleed hose (3) into an approved container and open the valve (5) to bleed the system pressure. The fuel connections are now safe for servicing.
4. Disconnect the fuel pressure gage from the fuel pressure connection. Refer to «Fuel Pressure Gage Installation and Removal»(ref-188786-S02796227162005090200000) .

SA9127E Gage Bar Set

J 37088-A Fuel Line Disconnect Tool Set. See Special Tools and Equipment .

Using The Fuel Pump

Scheme 100

Using the fuel pump to drain the tank is the easiest procedure if the pump is operable. The fuel can be pumped out with the vehicle on the ground or on the hoist.

On The Ground

1. Relieve the fuel system pressure. Refer to «Fuel Pressure Relief Procedure»(ref-188786-S07925041012005090200000) .
2. Disconnect the fuel feed line at the fuel rail and install the 3/8 inch x 1/4 inch quick connect from the SA9127E into the fuel feed line.
3. Connect a suitable drain hose to the other end of the adapter and connect the drain hose into a certified fuel handling cart.
4. Connect the scan tool to the vehicle and turn the ignition ON.
5. Energize the fuel pump using the scan tool. Refer to «Fuel System Diagnosis»(ref-188837-S15584422392005090200000) .
6. Pump out the fuel until no more than 1/4 tank remains.

On The Hoist

1. Connect the scan tool to the vehicle diagnostic connector and turn the ignition ON.
2. Relieve the fuel system pressure. Refer to «Fuel Pressure Relief Procedure»(ref-188786-S07925041012005090200000) .
3. Raise the vehicle on a hoist to a comfortable working height, keeping the scan tool outside of the vehicle and accessible from under the car.
4. Disconnect the chassis fuel feed line at fuel tank.
5. Install the 3/8 inch x 1/4 inch quick connect (1) adapter from the SA9127E onto the fuel feed line.
6. Connect a suitable drain hose to the other end of the adapter, and connect the drain hose to a certified fuel handling cart.
7. Energize the fuel pump using the scan tool. Refer to «Fuel System Diagnosis»(ref-188837-S15584422392005090200000) .
8. Pump out the fuel until no more than 1/4 tank remains.

Siphoning The Fuel Tank

If the fuel pump is inoperative, the tank can be drained by siphoning from the tank. A suitable means is through the fuel filler pipe with the correct type and stiffness of tubing as used with the SA9804E . See Special Tools and Equipment .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(ref-188769-S19455074222005090200000) in Engine Electrical.
2. Open the fuel filler door and remove the gas cap.
3. Insert the siphon hose guide/funnel into the fuel filler pipe.
4. Insert the SA9804E into the guide funnel and into the fuel filler pipe. See «Special Tools and Equipment»(ref-188786-S26486162762005090200000) . Some resistance may be encountered when the tip of the siphon hose reaches the inlet check valve. Repeated probing may be necessary to slide the hose tip through the check valve cage.
5. Begin the fuel siphoning process. Place the fuel into an approved fuel container.
6. Remove the siphon hose from the fuel filler pipe after draining is complete.

J 45722 Fuel Tank Lock Ring Remover

SA9156E Fuel Tank Lock Ring Remover

Fuel System Cleaning

1. Remove the fuel tank. Refer to «Fuel Tank Replacement»(ref-188786-S18407650372005090200000) .
2. Remove the fuel pump module assemblies. Refer to «Fuel Tank Module Replacement - Primary»(ref-188786-S27452618432005090200000) and «Fuel Tank Module Replacement - Secondary»(ref-188786-S41029793682005090200000) .
3. Inspect the fuel pump module strainer. Replace the pump module assembly if the fuel strainer is contaminated.
4. Flush the fuel tank with hot water.
5. Pour the water out of the fuel sender assembly opening in the fuel tank. Rock the fuel tank in order to be sure that the removal of the water from the fuel tank is complete.
6. Allow the tank to dry completely before reassembly.
7. Disconnect the fuel feed pipe at the engine fuel rail. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-188786-S09787054162005090200000) .
8. Clean the fuel pipes by applying air pressure in the opposite direction of the fuel flow.
9. Connect the fuel feed pipe to the engine fuel rail. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-188786-S09787054162005090200000) .
10. Install the fuel pump module assemblies. Refer to «Fuel Tank Module Replacement - Primary»(ref-188786-S27452618432005090200000) and «Fuel Tank Module Replacement - Secondary»(ref-188786-S41029793682005090200000) .
11. Install the fuel tank. Refer to «Fuel Tank Replacement»(ref-188786-S18407650372005090200000) .

J 41413 EVAP Pressure and Purge Station. See Special Tools and Equipment .

Cleaning Procedure

1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-188813-S15240900572005090200000) in General Information.
2. Remove the EVAP canister. Refer to «Evaporative Emission (EVAP) Canister Replacement»(ref-188785-S06815773232005090200000) .
3. Turn OFF the main valve on the J 41413 . See «Special Tools and Equipment»(ref-188786-S26486162762005090200000) .
4. Disconnect the hose from the diagnostic station pressure regulator.
5. Using a section of vacuum hose, connect one end onto the EVAP pressure/purge diagnostic station pressure regulator.
6. Connect the other end of the vacuum hose to the canister side of the purge pipe.
7. Turn ON the main nitrogen cylinder valve and continue to discharge nitrogen for 15 seconds.
8. If the nitrogen does not clear the blockage, replace the purge pipe.
9. Return the EVAP pressure/purge diagnostic station to the stations original condition.
10. Install a new EVAP canister. Refer to «Evaporative Emission (EVAP) Canister Replacement»(ref-188785-S06815773232005090200000) .
11. Lower the vehicle.
12. Install a new EVAP canister purge valve. Refer to «Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement»(ref-188786-S21196768692005090200000) .
13. Return to the diagnostic table that sent you here.

Spark Plug Usage

1. Ensure that the correct spark plug is installed. An incorrect spark plug causes driveability conditions. Refer to «Ignition System Specifications»(ref-188786-S18194948442005090200000) for the correct spark plug.
2. Ensure that the spark plug has the correct heat range. An incorrect heat range causes the following conditions: Spark plug fouling - colder plug Pre-ignition causing spark plug and/or engine damage - hotter plug

Control Module Learning Ability

The powertrain control module has a "learning" ability which enables the control module to make corrections for minor variations in the fuel system. These "learned values" can improve driveability. Disconnecting the battery resets the learning process. A change in the vehicle's performance may be noticed when a reset from a PCM power down occurs. Operating the vehicle under varying conditions will enable the control module to regain any lost vehicle performance.

In order to initiate the control module learning ability, warm the engine to operating temperature and drive the vehicle at part throttle with moderate acceleration. Continue to drive the vehicle while including steady cruise and idle speed operation. For the best idle speed quality several key cycles with a short drive and long idle periods is recommended.

PCM Output Controls

The powertrain control module (PCM) can be directed by a scan tool to operate certain solenoids, valves, motors, and switches. This scan tool function is generally referred to as Output Controls. The Output Controls can be found under Special Functions selection of the scan tool. Some Output Controls may be disabled by the PCM during certain types of vehicle operation. Operating a PCM controlled device with the scan tool should be limited to a maximum of ten seconds per test period.

Scheme 101

The provision for communicating with the control module is the data link connector (DLC). The DLC is located under the instrument panel to the left of the steering column. The DLC is used to connect to a scan tool. Some common uses of the scan tool are listed below

1. Identifying stored diagnostic trouble codes (DTCs)
2. Clearing the DTCs
3. Performing output control tests
4. Reading the serial data

Aftermarket (Add-On) Electrical and Vacuum Equipment

Note. Connect any add-on electrically operated equipment to the vehicle's electrical system at the battery (power and ground) in order to prevent damage to the vehicle.

Note. Do not attach add-on vacuum operated equipment to this vehicle. The use of add-on vacuum equipment may result in damage to vehicle components or systems.

Aftermarket (add-on) electrical and vacuum equipment is defined as any equipment installed on a vehicle after leaving the factory that connects to the vehicles electrical or vacuum systems. No allowances have been made in the vehicle design for addition of this type of equipment.

Add-on electrical equipment may cause the engine control system to malfunction even when the add-on electrical equipment is installed properly. Portable telephones and radios may also cause engine control system malfunctions even when not connected to the vehicles electrical system. The first step in diagnosing any engine control system problem is to remove all aftermarket electrical equipment from the vehicle. Diagnosis may proceed in the normal manner after eliminating aftermarket equipment as a cause of the engine control system malfunction.

Electrostatic Discharge (ESD) Damage

Note. In order to prevent possible Electrostatic Discharge damage to the PCM, Do Not touch the connector pins or the soldered components on the circuit board.

Electronic components used in the engine control system are often designed to operate at very low voltages. Electronic components are susceptible to damage caused by electrostatic discharge. Less than 100 volts of static electricity can cause damage to some of the electronic components. There are several ways for a person to become statically charged. The most common methods of charging are by friction and by induction. An example of charging by friction is a person sliding across a car seat. Charging by induction occurs when a person with well insulated shoes stands near a highly charged object and momentarily touches ground. Charges of the same polarity are drained off leaving the person highly charged with the opposite polarity. Therefore, use care when handling and testing electronic components in order to avoid electrostatic charges that can cause electronic component damage.

Input Components

The PCM supplies a buffered (reference) voltage to the various information sensors and switches. The PCM monitors the input components for circuit continuity and out-of-range values. The PCM also provides performance checking. Performance checking refers to the PCM indicating a fault when the signal from an input does not seem reasonable, i.e., a throttle position (TP) sensor that indicates a high throttle position at low engine loads or low manifold absolute pressure sensor voltage. The input components may include, but are not limited to the following sensors and switches

1. The crankshaft position (CKP) sensor
2. The camshaft position (CMP) sensor
3. The accelerator pedal position (APP) sensors
4. The serial data from the throttle actuator control (TAC) module
5. The engine coolant temperature (ECT) sensor
6. The intake air temperature (IAT) sensors
7. The heated oxygen sensors (HO2S)
8. The fuel tank pressure (FTP) sensor
9. The exhaust gas recirculation (EGR) valve position sensor
10. The vehicle speed sensor (VSS)
11. The rocker arm oil pressure switch
12. The power steering pressure (PSP) switch, if equipped
13. Transmission sensors and switches
14. A/C system sensors

Output Components

The PCM is responsible for the control and operation of many output components. The PCM controls many components with an electronic switch called an output driver that completes a ground circuit when turned ON. The PCM monitors the output components for the proper response to the PCM commands. Components where functional monitoring is not feasible will be monitored for circuit continuity and out-of-range values if applicable.

Output components to be monitored include, but are not limited to the following circuits

1. The throttle actuator control (TAC) motor
2. The rocker arm oil control solenoid valve
3. The exhaust gas recirculation (EGR) valve
4. The fuel pump relay
5. The evaporative emission (EVAP) system solenoids
6. The malfunction indicator lamp (MIL) control
7. The A/C compressor controls
8. The electronic transaxle controls

Purpose

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions

1. Accelerator pedal position sensing
2. Throttle positioning to meet driver and engine demands
3. Throttle position sensing
4. Internal diagnostics
5. Cruise control functions

The TAC system includes the following components

1. The accelerator pedal position (APP) sensors
2. The throttle body assembly
3. The powertrain control module (PCM)

Scheme 102

The accelerator pedal position (APP) sensor assembly (2) is fastened to the accelerator pedal assembly and attached to the brake pedal bracket (1). The APP sensor assembly contains two APP sensors that are operated by the accelerator pedal movement. The APP sensors 1 and 2 are potentiometer type sensors each with 3 circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The APP sensors are used to determine the pedal angle. The powertrain control module (PCM) provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors provide the PCM with signal voltage proportional to the pedal movement. APP sensor 1 signal voltage is low at the rest position and increases to near the 5-volt reference as the pedal is applied. APP sensor 2 signal is low at rest and also increases as the accelerator pedal is applied. APP sensor 2 increases at a different rate to approximately half the reference voltage. The APP sensor 1 is responsible for providing the actual pedal position to the PCM. The PCM then sends a throttle position target value to the TAC control module. APP sensor 2 provides a backup value to the APP sensor 1.

Scheme 103

The throttle body functions similar to a conventional throttle body with the following exceptions

1. An electric motor opens and closes the throttle valve.
2. The TAC module is an integral part of the throttle body assembly.
3. The throttle valve is spring loaded and the default position is slightly open.
4. There are 2 individual throttle position (TP) sensors integral to the TAC module cover.

The TP sensors are used to determine the throttle plate angle. The TP sensors provide the TAC module with a signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens. TP sensor 1 determines the actual throttle valve position. TP sensor 2 provides a backup value for TP sensor 1.

Throttle Actuator Control (TAC) Module

The throttle actuator control (TAC) module is the control center for the TAC system. The TAC module uses Read Only Memory (ROM) and Random Access Memory (RAM) along with an analog/digital (A/D) converter to control engine speed. The TAC module is self-diagnosing and communicates to the powertrain control module (PCM) with a dedicated serial data line. The TAC module receives accelerator pedal position (APP) sensor information from the PCM and provides diagnostic information to the PCM.

The APP sensor 1 enables the PCM to provide a target value to the TAC module in response to accelerator pedal movement. The TAC module achieves the correct throttle position by commanding the throttle control motor to position the throttle valve at the target value. The TAC module then compares the throttle position (TP) sensor 1 value to the target value. If necessary, the throttle control motor is moved slightly to obtain the exact desired position. The TAC module is not serviced separately and must be replaced with the throttle body assembly.

Powertrain Control Module

The powertrain control module (PCM) determines the drivers intent and then calculates the appropriate throttle response. This information is sent to the throttle actuator control (TAC) module through a dedicated serial data line.

Normal Mode

During the operation of the throttle actuator control (TAC) system, several modes or functions are considered normal. The following modes may be entered during normal operation

1. Learned idle mode-When ever the powertrain control module (PCM) recognizes the learned idle throttle position (TP) value, the engine operates in the learned idle mode. In the learned idle mode, the PCM uses stored engine performance settings in order to provide the best quality idle for all idle speed situations.
2. Learned idle TP values-The TAC module relies on a stored TP sensor value for optimum idle speed operation. After PCM replacement or PCM reset, a new TP sensor value is learned and stored in the PCM memory. Refer to the Idle Learn Procedure below.
3. Cold engine start mode-The throttle valve has a default start position that ensures improved cold engine starting and cold engine operation. In the cold engine start mode the TAC module commands the throttle control motor to the default position. In case of a TAC system malfunction, the default position spring opens the throttle valve to the default position.

Reduced Engine Power Mode

When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions

1. Acceleration limiting-The PCM will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
2. Limited throttle mode-The PCM will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
3. Throttle default mode-The PCM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
4. Forced idle mode-The PCM will perform the following actions: Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned OFF. Ignore the accelerator pedal input.
5. Engine shutdown mode-The PCM will disable fuel and de-energize the throttle actuator.

When performing certain maintenance procedures, or when performing certain vehicle repairs, the idle learn procedure must be initiated. On a new or reset powertrain control module (PCM), the learned idle position is determined by the throttle position (TP) sensor value that is recognized when the ignition is first turned ON. The value is then retained in memory. A new value is automatically calculated by the PCM whenever there no idle learn value stored in memory. The idle learn procedure begins the learning of a new idle position when there is no old idle position value in the PCM memory. Performing the idle learn procedure is required for the following conditions

1. The throttle body assembly is replaced
2. The throttle valve is cleaned-Deposits can build up in the throttle body requiring periodic cleaning of the throttle valve and throttle bore area. Refer to «Throttle Body Service»(ref-188786-S11328555002005090200000) .
3. The Clear DTCs function has been performed
4. The PCM has been programmed.
5. The PCM is replaced

If the PCM was replaced, proceed directly to the idle learn procedure. For the other actions above, the old learned idle position will be erased when the scan tool clear DTCs function is performed. Once the old learned idle position is erased, the idle learn procedure must be performed. Refer to Idle Learn Procedure .

TP Sensor Learned Value

On a new powertrain control module (PCM), the throttle position (TP) learned value is determined by the TP sensor value that is recognized when the ignition is first turned ON. The value is then retained in memory. This value is used as a baseline for a correlation between the TP input and the volume of intake air flow at idle. After many operating hours, deposits collect on the throttle plate and the bore of the throttle body. These deposits cause a restriction in the air flow at idle and can reduce engine performance at idle. In order to maintain engine idle quality, the PCM commands the throttle plate open slightly, correcting for the decreased air flow. Whenever this occurs, a new relationship is created between the TP sensor input and the actual throttle plate position. This relationship is the TP learned value.

When the throttle body is replaced, or the carbon deposits are removed, the TP learned value must be reset. If the value is not reset, the engine operates using stored values that are incorrect, resulting in a poor idle or hard starting. Resetting the TP learned value is required for the following conditions

1. The throttle body assembly is replaced
2. The throttle valve is cleaned-Deposits can build up in the throttle body requiring periodic cleaning of the throttle valve and throttle bore area. Refer to «Throttle Body Service»(ref-188786-S11328555002005090200000) .
3. The PCM has been programmed.
4. The PCM memory has been lost-as could happen with a long term power loss.

The TP learned value can be reset using the scan tool. Refer to Scan Tool Output Controls .

Fuel Filler Cap

The fuel fill pipe has a tethered fuel filler cap. A torque-limiting device prevents the cap from being over-tightened. To install the cap, turn the cap clockwise until you hear audible clicks. This indicates that the cap is correctly torqued and fully seated. A fuel filler cap that is not fully seated may cause a malfunction in the emission system.

Scheme 104

The primary fuel tank module is located inside of the right side of the fuel tank. The primary fuel tank module consists of the following major components

1. The fuel level sensor (4)
2. The fuel pump and reservoir assembly
3. The fuel strainer
4. The primary jet pump
5. The secondary jet pump
6. The fill limiter vent valve (6)
7. The fuel pressure sensor (1)
8. The fuel filter (3)
9. The fuel pressure regulator (5)
10. The fuel transfer pipe (2)

Scheme 105

The secondary fuel tank module is located inside of the left side of the fuel tank. The secondary fuel tank module consists of the following major components

1. The fuel level sensor (1)
2. The fuel pick-up (2)

Fuel Level Sensor

The fuel level sensor consists of a float, a wire float arm, and a ceramic resistor card. The position of the float arm indicates the fuel level. The fuel level sensor contains a variable resistor which changes resistance in correspondence with the position of the float arm. The control module sends the fuel level information via the CAN serial data to the body control module (BCM). The instrument panel cluster (IPC) displays the fuel level as determined by the BCM. This information is used for the IPC fuel gage and the low fuel warning indicator, if applicable. The control module also monitors the fuel level input for various diagnostics.

Scheme 106

The fuel pump (2) is mounted in the primary fuel tank module reservoir. The fuel pump is an electric high-pressure pump. Fuel is pumped to the fuel injection system at a specified flow and pressure. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers. The control module controls the electric fuel pump operation through a fuel pump relay.

Scheme 107

The primary jet pump (1) is located in the primary fuel tank module. Fuel pump flow loss, caused by vapor expulsion in the pump inlet chamber, is diverted to the primary jet pump and the secondary jet pump (2) through a restrictive orifice located on the pump cover. The primary jet pump fills the reservoir of the primary fuel tank module.

Scheme 108

The secondary jet pump (1) creates a venturi action which causes the fuel to be drawn from the secondary side of the fuel tank, through the transfer pipe, to the primary side of the fuel tank.

Fuel Strainer

The fuel strainer attaches to the lower end of the primary fuel tank module. The fuel strainer is made of woven plastic. The functions of the fuel strainer are to filter contaminants and to wick fuel. The fuel strainer normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or contamination.

Fuel Filter

The fuel filter (1) is located in the primary fuel tank module. The paper filter element traps particles in the fuel that may damage the fuel injection system. The filter housing is made to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature.

Fuel Pressure Regulator

The fuel pressure regulator is integrated into the fuel filter cover on the primary fuel tank module. The fuel pressure regulator uses a spring with a preset tension and a stainless steel ball inserted into a precision ground seat in order to regulate fuel pressure. This type of fuel pressure regulator is not serviceable.

Fuel Feed Pipes

The fuel feed pipe carries fuel from the fuel tank to the fuel injection system. The fuel pipe consists of 3 sections

1. The rear fuel pipe is located from the top of the fuel tank to the chassis fuel pipe. The rear fuel pipe is constructed of nylon.
2. The chassis fuel pipe is located under the vehicle and connects the rear fuel pipe to the engine compartment fuel pipe. The chassis fuel pipe is constructed of steel with a section of rubber hose.
3. The engine compartment fuel pipe connects the chassis fuel feed pipe to the fuel rail. The engine compartment fuel pipe is constructed of steel.

Nylon Fuel Pipes

Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. The following 2 sizes of nylon pipes are used

1. 9.53 mm (3/8 in) ID for the fuel feed
2. 12.7 mm (1/2 in) ID for the vent

Heat resistant rubber hose or corrugated plastic conduit protect the sections of the pipes that are exposed to chafing, high temperature, or vibration.

Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if nylon fuel pipes are forced into sharp bends, the pipes kink and restrict the fuel flow. Also, once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far. Take special care when working on a vehicle with nylon fuel pipes.

Quick-Connect Fittings

Quick-connect fittings provide a simplified means of installing and connecting fuel system components. The fittings consist of a unique female connector and a compatible male pipe end. O-rings, located inside the female connector, provide the fuel seal. Integral locking tabs inside the female connector hold the fittings together.

Fuel Pipe O-rings

O-rings seal the threaded connections in the fuel system. The fuel system O-ring seals are made of special material. Service the O-ring seals with the correct service part.

Scheme 109

The on-board refueling vapor recovery (ORVR) system is an on-board vehicle system designed to recover fuel vapors during the vehicle refueling operation. Instead of allowing fuel vapors to escape to the atmosphere the ORVR system transports the vapor to the EVAP canister for use by the engine. The flow of liquid fuel down the fuel filler neck provides a liquid seal that prevents fuel vapor from leaving the fuel system. The ORVR system architecture varies from platform to platform. Some of the items listed below are optional depending on the platform application. The following is a list of all the ORVR system components with a brief description of their operation

1. The EVAP canister (1). The EVAP canister receives and stores refueling vapor from the fuel system. The EVAP canister releases the fuel vapor to the engine through the EVAP control system.
2. The vapor lines (2). The vapor lines transport fuel vapor from the fuel tank assembly to the EVAP canister.
3. The vapor recirculation line (3), if equipped. The vapor recirculation line transports fuel vapor from the fuel tank to the top of the fuel filler pipe during refueling in order to reduce the fuel vapor at the canister. The vapor recirculation line can be located inside the fuel filler pipe or outside of the fuel filler pipe.
4. The variable orifice valve (4), if equipped. The variable orifice valve regulates the amount of vapor allowed to enter the vapor recirculation line.
5. The fuel filler pipe (5). The fuel filler pipe carries fuel from the fuel dispensing nozzle to the fuel tank.
6. The check valve (6). The check valve limits fuel spitback from the fuel tank during the refueling operation by allowing fuel flow only into the fuel tank. The check valve is located at the bottom of the fuel filler pipe or in the fuel tank filler neck.
7. The fuel sender assembly (7). The fuel sender assembly pumps fuel to the engine from the fuel tank.
8. The fill limiter vent valve (8). The fill limiter vent valve is located in the fuel tank and acts as a shut-off valve. The fill limiter vent valve performs the following functions: Controls the fuel tank fill level by closing the primary vent of the fuel tank. Prevents liquid fuel from exiting the fuel tank through the vapor line and entering the EVAP canister. Provides fuel-spillage protection in the event of a vehicle rollover by closing the vapor path from the tank to the EVAP canister.
9. The pressure/vacuum relief valve (9), if equipped. The pressure/vacuum relief valve provides venting of excessive fuel tank pressure or vacuum. The pressure/vacuum relief valve is located in the fuel filler neck on a plastic fuel tank and in the fill limiter vent valve on a steel fuel tank.

Fuel Metering System

The function of the fuel metering system is deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered to each cylinder by the fuel injectors. The fuel injectors are controlled sequentially by the powertrain control module (PCM). The PCM bases the control of the fuel injectors on several important engine parameters. These engine parameters include the following

1. Engine speed (RPM)
2. Accelerator pedal position (APP)
3. Engine coolant temperature (ECT)
4. Intake air temperature (IAT)
5. Manifold absolute pressure (MAP)
6. Fuel control oxygen sensor input (HO2S 1)

Scheme 110

The fuel rail is mounted on the intake manifold and distributes the fuel to each cylinder through the individual injectors. The fuel is delivered from the pump through the fuel supply line to the inlet pipe of the fuel rail. The fuel inlet pipe directs fuel to both the front and the rear fuel rails (1) suppling the individual fuel injector (4).

Scheme 111

The fuel injector is an electromagnetic (solenoid) type injection nozzle which injects fuel into the intake port of the cylinder head according to the signals from the powertrain control module (PCM). There are 6 fuel injectors, one for each cylinder, located between the intake manifold and the fuel rail.

The PCM energizes the solenoid coil of the fuel injector, generating an electromagnet field that attracts the solenoid plunger. The needle valve, which is incorporated with the solenoid plunger, is opened by the movement of the solenoid plunger. The opening of the needle valve allows fuel that is under pressure to disperse into a cone shaped pattern. Because the stroke of the needle valve in the fuel injector is set constant, the amount of fuel injected at one time is determined by the pulse width injection time-the length of time the solenoid coil is energized.

The fuel injectors may cause various driveability concerns if the following conditions occur

1. If the injectors will not open
2. If the injectors are stuck open
3. If the injectors are leaking
4. If the injectors have a low or high coil resistance

Engine Fueling

The engine is fueled by 6 individual fuel injectors, one for each cylinder, that are controlled by the PCM. Each fuel injector is fired individually in the engine firing order, which is called a sequential multiport fuel injection. The PCM controls each fuel injector by energizing the fuel injector coil for a brief period once every other engine revolution. The length of this brief period, or pulse, is carefully calculated by the control module in order to deliver the correct amount of fuel for proper driveability and emissions control. The period of time when the fuel injector is energized is called the pulse width and is measured in milliseconds, thousandths of a second.

While the engine is running, the PCM is constantly monitoring the inputs and recalculating the appropriate pulse width for each fuel injector. The pulse width calculation is based on the fuel injector flow rate, mass of fuel the energized fuel injector will pass per unit of time, the desired air/fuel ratio, and actual air mass in each cylinder and is adjusted for battery voltage, short term, and long term fuel trim. The calculated pulse is timed to occur as each cylinders intake valves are closing to attain largest duration and most vaporization.

Fueling during an engine crank is slightly different than fueling during an engine run. As the engine begins to turn, a prime pulse may be injected to speed starting. As soon as the PCM can determine where in the firing order the engine is, the PCM begins pulsing the fuel injectors. The pulse width during the crank is based on the coolant temperature and the engine load.

The fueling system has several automatic adjustments in order to compensate for the differences in the fuel system hardware, the driving conditions, the fuel used, and the vehicle aging. The basis for the fuel control is the pulse width calculation that is described above. Included in this calculation are an adjustment for the battery voltage, the short term fuel trim, and the long term fuel trim. The battery voltage adjustment is necessary since the changes in the voltage across the fuel injector affect the fuel injector flow rate. The short term and the long term fuel trims are fine and gross adjustments to the pulse width that are designed in order to maximize the driveability and emissions control. These fuel trims are based on the feedback from the oxygen sensors in the exhaust stream and are only used when the fuel control system is in a Closed Loop operation.

Fuel Trim Operation

Synchronous Injection

There are two types of injection timing. One is synchronous injection, when fuel injection is synchronous with the ignition signal or the signal from the camshaft position (CMP) sensor. The other is asynchronous injection, when fuel injection takes place independently of the ignition signal or the signal from the CMP sensor.

When starting the engine, the fuel injectors inject the fuel simultaneously and synchronously at every camshaft position (CMP) sensor signal. When the engine is starting at a cold state, the amount of fuel is determined by the engine coolant temperature (ECT) sensor and is divided and injected.

Once the engine is running, the fuel injection occurs in a cylinder only when the cylinder is in the exhaust stroke. The PCM detects the compression stroke of cylinder 1 through the CMP sensor signal.

Asynchronous Injection

Whenever a change in the throttle valve opening exceeds a specified value, as determined by the PCM, additional fuel is injected simultaneously into the cylinders which are in the intake and exhaust strokes. This is in addition to the above synchronous injection and is not based on the ignition signal.

Engine Starting Enrichment

In order to improve starting performance, fuel enrichment during start up is carried out. For a certain time after the engine is started, the air/fuel mixture is enriched slightly in order to stabilize the engine speed. The amount of compensation varies depending on the engine coolant temperature as measured by the ECT sensor.

Engine Warm-Up Enrichment

When the engine is cold, additional fuel is added in order to ensure good driveability. The level of initial enrichment is determined by the engine coolant temperature (ECT) sensor and intake air temperature (IAT) sensor input. The air/fuel mixture enrichment is gradually decreased until the ECT sensor reaches a specified value.

Acceleration Enrichment

During acceleration, the pulse width of the fuel injectors is lengthened in order to deliver more fuel. The additional fuel that is required is relative to throttle position (TP) sensor and manifold absolute pressure (MAP) sensor input. Acceleration Enrichment ensures smooth and reliable engine acceleration.

High Engine Load Enrichment

In order to provide maximum power during high engine load driving conditions, the air/fuel mixture is enriched when the MAP senor input within a specified PCM calibrated value.

System Voltage Compensation

A power supply system voltage drop will delay the mechanical operation of the fuel injector. The actual injector ON time becomes shorter when the system voltage decreases. In order to compensate for this, the fuel injector pulse width signal is lengthened.

Base Air/Fuel Ratio Compensation

The base air/fuel ratio may vary due to differences in individual engines and mileage. In order to compensate for such variations, feedback information is used to adjust the base air/fuel mixture to maintain the optimum air/fuel ratio.

Fuel Cutoff

Fuel cutoff occurs when the PCM stops fuel injection or turns off the fuel pump. Fuel cutoff is used during the following conditions

1. During deceleration, when the throttle valve is closed and engine speed is high, fuel injection is stopped so that unburned gas will not be exhausted. Fuel injection starts again when the above conditions are no longer present.
2. When engine speed exceeds 5,000 RPM with no load.
3. When a throttle actuator control (TAC) system malfunction is detected, the engine speed is limited to a maximum of 2,600 RPM.
4. When a accelerator pedal position (APP) malfunction is detected, the engine speed is limited to a maximum of 3,200 RPM.
5. In order to minimize any possible fuel spillage during an airbag deployment event, the fuel pump is de-energized,. The PCM receives a signal from the supplemental inflatable restraint (SIR) system and turns off the fuel pump relay. The relay is re-energized once the ignition switch is cycled off and then on again.

EVAP System Components

The evaporative emission (EVAP) system consists of the following components

EVAP Canister

The canister is filled with carbon pellets used to absorb and store fuel vapors. Fuel vapor is stored in the canister until the control module determines that the vapor can be consumed in the normal combustion process.

EVAP Purge Valve

The EVAP purge valve controls the flow of vapors from the EVAP system to the intake manifold. This normally closed valve is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.

EVAP Vent Valve

The EVAP vent valve controls fresh airflow into the EVAP canister. The valve is normally open. The control module will command the valve closed during some EVAP tests, allowing the system to be tested for leaks.

Fuel Tank Pressure Sensor

The fuel tank pressure (FTP) sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1-4.9 volts. As FTP increases, FTP sensor voltage decreases, high pressure, = low voltage. As FTP decreases, FTP sensor voltage increases low pressure or vacuum = high voltage.

EVAP Service Port

The EVAP service port is located in the EVAP purge pipe between the EVAP purge valve and the EVAP canister. The service port is identified by a green colored cap.

Camshaft Position (CMP) Sensor

The CMP sensor is a signal generator that is composed of a magnet and a coil with an iron core. The PCM relies on the AC signal provided by the CMP sensor in order perform the following

1. To optimize the ignition timing
2. To optimize the fuel delivery
3. To detect any engine misfire

Scheme 112

The camshaft position (CMP) sensor (1) is fastened to the backside of the timing belt cover (2) of the left bank cylinder head. The cam gear (4) is attached to the left bank camshaft (3) inside the timing belt cover (2). The CMP sensor signal rotor is integral to the cam gear (4). The signal rotor has three unevenly spaced teeth. When each tooth of the signal rotor moves past the CMP sensor (1), an electrical signal is generated. These AC signals, three per camshaft revolution, are sent to the PCM.

Knock Sensor (KS)

The knock sensor (KS) is located below the intake manifold, on the engine block between the left and right side engine cylinders. The KS detects engine detonation and sends a signal to the PCM. The PCM uses the input from the KS to adjust the ignition timing in order to control detonation. For detailed information on the operation of the KS refer to Knock Sensor (KS) System Description .

Noteworthy Ignition Information

Consider the following important information when servicing the ignition system

1. The ignition coils secondary output voltage is more than 40,000 volts. Avoid body contact with the ignition high voltage secondary components when the engine is running or personal injury may result.
2. The ignition timing is not adjustable. A timing indicator and timing marks are still visible at the crankshaft pulley but are not used to set or adjust the ignition timing. The PCM provides all ignition timing adjustments electronically.
3. Be careful not to damage the secondary ignition coil boots when servicing the ignition system. Rotate each ignition coil in order to loosen the boot from the spark plug before removing. Never pierce a secondary ignition boot for any testing purposes. Future ignition system problems are guaranteed if pinpoints or test lights are pushed through the secondary ignition component insulation during testing.
4. Do not use a conventional tachometer in order to check the engine speed on this ignition system. An inductive type pick-up will not provide reliable engine speed information. Use a scan tool in order to monitor the engine RPM.

Scheme 113

The 3.5L engine is equipped with a knock sensor (KS) (1) that is located on the engine block underneath the intake manifold. Ignition timing determines the relationship between the time the spark plug is fired and the time that the piston reaches top dead center (TDC). TDC is the point in time when the piston achieves maximum upward travel in the cylinder. If the spark plug ignites the compressed air/fuel mixture too late, not all of the air/fuel mixture has time to burn while the fuel is highly compressed. Late ignition causes a decrease in fuel efficiency, decreased power, and increased exhaust emissions. If the spark plug fires too soon, too much of the air/fuel mixture starts burning before the piston reaches the top of the compression stroke. Early ignition of the air/fuel mixture causes detonation, commonly referred to as spark knock. Constant spark knock in the motor is undesirable. Excessive spark knock can reduce engine performance. If severe enough, detonation can cause engine damage.

Every engine has an optimum ignition timing value. The optimum ignition timing is usually the earliest or most advanced firing of the spark plug that is possible without causing detonation. An engines optimum ignition timing is designed to be the most advanced ignition timing possible during the most demanding conditions. The optimum ignition timing is affected by all of the following variables

1. The engine load
2. The engine temperature
3. The atmospheric pressure
4. The fuel quality
5. The fuel's octane rating

Ignition systems equipped with a knock sensor (KS) can be engineered for optimum ignition timing. A KS detects when the engine is experiencing detonation and then signals the PCM to reduce the spark advance until detonation is no longer detected.

Scheme 114

The KS detects when the engine is experiencing detonation. The KS (1) has a Piezo ceramic element (3) that generates a signal at the same resonance point as the expected knocking frequency of the engine. When engine detonation is detected, the sensor signals the PCM to reduce the spark advance until detonation is no longer detected.

In response to the KS signal the PCM retards the spark advance in order to reduce the detonation. The amount of timing retard that the PCM applies is based on the engine speed and the length of time that the engine detonation is detected. Once the spark timing is retarded, the KS circuitry in the PCM performs calculations in order to determine how much spark advance should be re-introduced. Normally the ignition timing advance is increased until zero retard, or normal ignition timing, is re-established. If detonation occurs again, the whole cycle will repeat. The alteration of the ignition timing by the KS often occurs continuously while the engine is running, even though no detonation is heard by the vehicle's operator.

Engine Idle Speed Control

The engine idle speed is controlled by the powertrain control module (PCM) through the throttle actuator control (TAC) motor located in the TAC module assembly. There are several reasons for idle speed control

1. In order to maintain the engine idle speed at the specified RPM at all times. The engine idle speed can vary due to any of the following reasons: A change in the load applied to engine such as when the rear defogger is operating, the automatic transaxle is shifted to R, D, 2 or L ranges, the A/C is turned ON, the headlights or stop lights are turned ON, etc. A change in the atmospheric pressure. A change in the engine's condition over time.
2. In order to improve the starting performance of the engine.
3. In order to improve the driveability of the engine during warm up.
4. In order to compensate for the change in the air/fuel mixture ratio when decelerating.

Intake Air Temperature (IAT) Sensors

The intake air temperature (IAT) sensor 1 is located in the inlet air duct between the air cleaner and the throttle body. The intake air temperature (IAT) sensor 2 is mounted in the front of the intake manifold just behind the throttle body. The IAT sensors measure the temperature of the air at their respective locations in the intake system. The IAT sensors provide useful air temperature information to the powertrain control module (PCM).

Each IAT sensor is a thermistor-a resistor whose resistance changes as a function of temperature. When the temperature is low, the resistance is high. The resistance decreases as the temperature increases. The IAT sensor is a 2-wire circuit with a reference or signal voltage and a ground coming from the PCM.

IAT Sensor Operation

Throttle Position (TP) Sensors

There are 2 throttle position (TP) sensors, both located in the molded side cover of the TAC module assembly. Each is a potentiometer connected to the throttle shaft of the throttle body. By monitoring the voltage on the signal line, the logic circuits in the throttle actuator control (TAC) module calculate the throttle position. When the TAC motor changes the throttle valve angle in response to accelerator pedal movement, the two TP sensor signal voltage outputs also change. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens. TP sensor 1 determines the actual throttle valve position. TP sensor 2 provides a backup value for TP sensor 1. For detailed information on the operation of the TAC system refer to Throttle Actuator Control (TAC) System Description .

Because the position of the throttle valve controls the air supply to the engine, the powertrain control module (PCM) will modify the fuel delivery based on the throttle angle. For example, power enrichment occurs when the throttle angle approaches wide-open throttle. The PCM looks primarily for changes in the manifold absolute pressure (MAP) sensor and TP sensor outputs in order to control fuel delivery.