Engine Controls and Fuel - 1.4l (Luu) - Description and Operation Cadillac ELR I

Scheme 52

Camshaft Position (CMP) Actuator System

The camshaft position (CMP) actuator system is an electro-hydraulic operated device used for a variety of engine performance and operational enhancements. These enhancements include lower emission output through exhaust gas dilution of the intake charge in the combustion chamber, a broader engine torque range, and improved fuel economy. The CMP actuator system accomplishes this by changing the angle or timing of the camshaft relative to the crankshaft position. The CMP actuator simply allows earlier or later intake and exhaust valve opening during the four stroke engine cycle. The CMP actuator cannot vary the duration of valve opening, or the valve lift.

During engine Off, engine idling conditions, and engine shutdown, the camshaft actuator is held in the Park position. Internal to the CMP actuator assembly is a return spring and a locking pin. During non-phasing modes of the camshaft, the return spring rotates the camshaft back to the Park position, and the locking pin retains the CMP actuator sprocket to the camshaft.

CMP Actuator System Operation

The CMP actuator system is controlled by the engine control module (ECM). The ECM sends a signal to a CMP actuator solenoid in order to control the amount of engine oil flow to a Cam Actuator passage. The pressurized engine oil is sent to unseat the locking pin, and to the vane and rotor assembly of the CMP actuator. There are 2 different passages for oil to flow through, a passage for cam advance and a passage for cam retard. The Cam Actuator is attached to a camshaft and is hydraulically operated in order to change the angle of the camshaft relative to crankshaft position (CKP). Engine oil pressure (EOP), viscosity, temperature and engine oil level can have an adverse affect on Cam Actuator performance.

Electronic Ignition System Operation

The electronic ignition system produces and controls the high energy secondary spark. This spark ignites the compressed air/fuel mixture at precisely the correct time, providing optimal performance, fuel economy, and control of exhaust emissions. The engine control module (ECM) collects information from the crankshaft position sensor and the intake/exhaust camshaft position sensors to determine the sequence, dwell, and timing of the spark for each cylinder. The ECM transmits a frequency signal to the ignition coil module on the individual ignition control circuits to fire the spark plugs.

Crankshaft Position Sensor

The crankshaft position sensor is an externally magnetically biased digital output integrated circuit sensing device. The sensor provides a pulse for each magnetic pole of the encoder wheel on the crankshaft. The sensor produces an ON/OFF DC voltage of varying frequency, with 58 output pulses per crankshaft revolution. The frequency of the sensor output depends on the velocity of the crankshaft. The ECM uses sensor signal pulse to determine crankshaft speed and position to calculate the best timing for ignition and fuel injection. The ECM also uses the crankshaft position sensor information to control camshaft phasing and to detect cylinder misfire.

The ECM also has a dedicated replicated crankshaft position sensor signal output circuit that may be used as an input signal to other modules for monitoring engine RPM.

The crankshaft position sensor is connected to the engine control module by the circuits listed below

1. A 5 V reference circuit
2. A low reference circuit
3. A signal circuit

Crankshaft Encoder Wheel

The crankshaft encoder wheel is part of the crankshaft. The encoder wheel consists of 58 tooth and a reference gap. Each tooth on the encoder wheel is spaced 6° apart with a 12° space for the reference gap. The pulse from the reference gap is known as the sync pulse. The sync pulse is used to synchronize the ignition coil module firing sequence with the crankshaft position while the other tooth provides cylinder location during a revolution.

Camshaft Position Sensors

The intake and exhaust camshaft position sensors are each triggered by a notched reluctor wheel built onto the camshaft sprockets. The four signal pulses occur every camshaft revolution. Each notch is a different size which is used to identify the compression stroke of each cylinder and to enable sequential fuel injection. The camshaft position sensors are connected to the ECM by the circuits listed below

1. A 5 V reference circuit
2. A low reference circuit
3. A signal circuit

Ignition Coil Module

The ignition coil module integrates the 4 coils and the ignition control module within a single sealed component.

The ignition coil module has the following circuits

1. An ignition voltage circuit
2. A ground
3. A low reference circuit
4. 4 ignition coil control circuits

The ECM controls the individual coils by transmitting timing pulses on the ignition coil control circuit to each ignition coil to enable a spark event.

The spark plugs are connected to each coil by a short boot. The boot contains a spring that conducts the spark energy from the coil to the spark plug. The spark plug electrode is coated with platinum for long wear and higher efficiency.

Engine Control Module (ECM)

The ECM controls all ignition system functions and constantly adjusts the spark timing. The ECM monitors information from various sensor inputs that include the following

1. The crankshaft position sensor
2. The accelerator pedal position (APP)
3. The manifold absolute pressure (MAP) sensor
4. The intake air temperature (IAT) sensor
5. The vehicle speed sensor (VSS)
6. The engine knock sensor
7. The engine coolant temperature (ECT) sensor
8. The mass airflow (MAF) sensor
9. The camshaft position sensors

Engine Control Module Description

The Engine Control Module (ECM) interacts with many emission related components and systems, and monitors emission related components and systems for deterioration. OBD II diagnostics monitor the system performance and a diagnostic trouble code (DTC) sets if the system performance degrades. The ECM is part of a network and communicates with various other vehicle control modules.

Malfunction indicator lamp (MIL) operation and DTC storage are dictated by the DTC type. A DTC is ranked as a Type A or Type B if the DTC is emissions related. Type C is a non-emissions related DTC.

The ECM is the control center of the engine controls system. Review the components and wiring diagrams in order to determine which systems are controlled by the ECM.

The ECM constantly monitors the information from various sensors and other inputs, and controls the systems that affect engine performance and emissions. The ECM also performs diagnostic tests on various parts of the system and can turn on the MIL when it recognizes an operational problem that affects emissions. When the ECM detects a malfunction, the ECM stores a DTC. The condition area is identified by the particular DTC that is set. This aids the technician in making repairs.

ECM Function

The ECM can supply 5 V or 12 V to various sensors or switches. This is done through pull-up resistors to regulated power supplies within the ECM. In some cases, even an ordinary shop voltmeter will not give an accurate reading due to low input resistance. Therefore, a digital multimeter (DMM) with at least 10 megaohms input impedance is required in order to ensure accurate voltage readings.

The ECM controls the output circuits by controlling the ground or the power feed circuit through transistors or a device called an output driver module.

EEPROM

The electronically erasable programmable read only memory (EEPROM) is an integral part of the ECM. The EEPROM contains program and calibration information that the ECM needs in order to control engine operation.

Special equipment, as well as the correct program and calibration for the vehicle, are required in order to reprogram the ECM.

Data Link Connector (DLC)

The data link connector (DLC) provides serial data communication for ECM diagnosis. This connector allows the technician to use a scan tool in order to monitor various serial data parameters, and display DTC information. The DLC is located inside the driver's compartment, underneath the instrument panel.

Malfunction Indicator Lamp (MIL)

The malfunction indicator lamp (MIL) is inside the instrument panel cluster (IPC). The MIL is controlled by the ECM and illuminates when the ECM detects a condition that affects vehicle emissions.

ECM Service Precautions

The ECM, by design, can withstand normal current draws that are associated with vehicle operations. However, care must be used in order to avoid overloading any of these circuits. When testing for opens or shorts, do not ground or apply voltage to any of the ECM circuits unless the diagnostic procedure instructs you to do so. These circuits should only be tested with a DMM unless the diagnostic procedure instructs otherwise.

Emissions Diagnosis For State I/M Programs

This OBD II equipped vehicle is designed to diagnose any conditions that could lead to excessive levels of the following emissions

1. Hydrocarbons (HC)
2. Carbon monoxide (CO)
3. Oxides of nitrogen (NOx)
4. Evaporative emission (EVAP) system losses

Should this vehicle's on-board diagnostic system (ECM) detect a condition that could result in excessive emissions, the ECM turns ON the MIL and stores a DTC that is associated with the condition.

Aftermarket (Add-On) Electrical And Vacuum Equipment

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

Add-on electrical equipment, even when installed to these strict guidelines, may still cause the powertrain system to malfunction. This may also include equipment not connected to the vehicle electrical system, such as portable telephones and radios. Therefore, the first step in diagnosing any powertrain condition is to eliminate all of the aftermarket electrical equipment from the vehicle. After this is done, if the problem still exists, the problem may be diagnosed in the normal manner.

Electrostatic Discharge (ESD) Damage

Note. In order to prevent possible electrostatic discharge damage to the ECM, DO NOT touch the connector pins on the ECM.

The electronic components that are used in the control systems are often designed to carry very low voltage. These electronic components are susceptible to damage caused by electrostatic discharge. Less than 100 V of static electricity can cause damage to some electronic components. By comparison, it takes as much as 4,000 V for a person to even feel a static discharge.

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. Static charges can cause damage, therefore, it is important to use care when handling and testing electronic components.

Emissions Control Information Label

The underhood Vehicle Emissions Control Information Label contains important emission specifications. This identifies the year, the displacement of the engine in liters, and the class of the vehicle.

This label is located in the engine compartment of every General Motors vehicle. If the label has been removed, it can be ordered from GM service parts operations (GMSPO).

Maintenance Mode Description

The maintenance modes are automated engine run cycles performed to mitigate the potential adverse affects to internal combustion engine (ICE) components due to limited or no engine run time. The engine control module (ECM) monitors ICE run time and fuel age and invokes the engine maintenance mode or the fuel maintenance mode when the threshold criteria is exceeded. Limited engine run time can result in component degradation, combustion by-product (water/fuel) accumulation in engine oil, and stale gasoline which can lead to the following conditions

1. Insufficient engine lubrication
2. Flat spots in bearings
3. Water pump belt damage
4. Fuel pump failure
5. Blocked/restricted fuel injectors
6. Rough engine operation due to stale fuel

The maintenance modes are also necessary to exercise emissions related equipment and to reduce the possibility of ICE no-start conditions. The ICE must start every time to prevent the vehicle occupants from being stranded.

Engine Maintenance Mode

The engine maintenance mode will run every 42 days if the ECM determines that the ICE run time has not been sufficient enough to purge the contaminants from the engine oil. The ECM commands the ICE to run for a contaminant burn-off time of at least 30 s after the engine coolant temperature (ECT) reaches 65°C (149°F), unless cold starts have been experienced since the last engine maintenance mode event. Between 15-90 s are added to the required contaminant burn-off time each time all of the following cold start criteria are met

1. ECT and intake air temperature (IAT) are within 8°C (14°F) at engine start up.
2. ECT and IAT are less than 20°C (68°F) at engine start up.
3. ECT does not exceed 65°C (149°F) during the run cycle.

If an ECT or IAT sensor fault is present at an initial ignition cycle engine run event, a default time will be added to the required contaminant burn-off time.

The ICE runs continuously while the engine maintenance mode is active.

At power down, ICE run time duration above 65°C (149°F) ECT, is subtracted from the required contaminant burn-off time.

The engine maintenance mode timer (days since engine run) is reset to 0 when the required contaminant burn-off time is complete.

Fuel Maintenance Mode

When the ECM determines that the fuel age is greater than 365 days, the ICE will run until the fuel level is less than 1/3 tank. The ICE will cycle ON and OFF and will run as efficiently as possible while the fuel maintenance mode is active.

Scheme 53

EVAP System Operation

The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the EVAP vapor tube, into the EVAP canister. Carbon in the canister adsorbs and stores the fuel vapors. The EVAP canister stores the fuel vapors until the engine is able to use them.

This vehicles sealed fuel system features a normally sealed fuel tank and canister to reduce canister loading during daily cycles. Different than the EVAP diagnostic hardware from conventional EVAP systems this vent solenoid valve is normally closed. This keeps the fuel vapor sealed in the fuel tank and canister. The vent solenoid valve is only open for canister purge, refueling, fuel tank pressure (FTP) sensor correlation or leak check with the EVAP leak detection pump. Additional, excessive pressure is vented through the vent hose and EVAP canister vent solenoid valve to the atmosphere at a predetermined limit. Diagnostics are performed with the propulsion system ON and OFF.

Propulsion System OFF

The engine control module (ECM) wake-up timer, which is located in the Hybrid Powertrain Control Module 2, activates the ECM at three predetermined times so that leak detection can occur. This is where the EVAP leak detection pump hardware is used. The ECM uses several tests to determine if the EVAP system is leaking or restricted. These tests execute with the engine OFF at 5, 7, or 9.5 hours after the vehicle has been shut OFF. These soak times allow the fuel temperature and pressure to stabilized.

Propulsion System ON

EVAP purge flow, FTP sensor and EVAP leak detection pump sensor performance diagnostics are conducted.

Purge Solenoid Valve Leak Test

This vehicle does not have a purge solenoid leak test. A leaking purge solenoid will set DTCs P0442 or P0455.

Large Leak Test

This vehicle does not have a engine running version of the large leak diagnostic. The large leak diagnostic only runs when the propulsion system is not active. This is accomplished by using the EVAP leak detection pump hardware and a prior refueling event was detected.

Small Leak Test

This vehicle does not use the engine OFF natural vacuum diagnostic for small leak detection. Instead it uses the EVAP leak detection pump hardware. This test executes when the propulsion is not active at 5, 7, or 9.5 hours after the vehicle has been shut OFF.

EVAP System Components

The EVAP system consists of the following components

EVAP Purge Solenoid Valve

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

EVAP Canister

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

Fuel Tank Pressure Sensor

The FTP sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The ECM provides 5 V reference, ground and signal circuit to the FTP sensor. Depending on the vehicle, the sensor can be located in the vapor space on top of the fuel tank, in the vapor tube between the canister and the tank, or on the EVAP canister. The FTP sensor provides a signal voltage back to the ECM that can vary between 0.15-4.85 V. A high FTP sensor voltage indicates a fuel tank pressure. A low FTP sensor voltage indicates a fuel tank vacuum.

EVAP Vent Solenoid Valve

The EVAP vent solenoid valve controls fresh airflow into the EVAP canister. The EVAP vent solenoid valve is normally closed. This keeps vent fuel vapor sealed in the fuel tank and canister. The EVAP vent solenoid valve is similar to a conventional vent valve, but a conventional vent valve is normally open. This vent solenoid valve is only open for canister purge, refueling, fuel tank pressure sensor correlation or leak check with the EVAP leak detection pump.

Relief Valve

This is a mechanical pressure relieve valve that is part of the vent solenoid valve assembly. It protects the fuel tank by relieving excessive pressure or excessive vacuum that could build up in the sealed fuel tank from environmental changes.

EVAP Leak Detection Pump Assembly

The leak detection pump assembly consists of three main components. These components are integral parts of the EVAP leak detection pump assembly and are not serviceable.

1. EVAP leak detection pump with reference orifice
2. EVAP leak detection pump switching valve
3. EVAP leak detection pump pressure sensor

This leak detection pump assembly is used for FTP sensor correlation and leak checking the EVAP system for small and large system leaks.

1. EVAP leak detection pump pressure sensor's primary purpose is to perform leak detection diagnostics. The sensor itself is diagnosed by a correlation to barometric pressure based off the MAP sensor.
2. EVAP leak detection pump 0.51mm (0.020 in) reference orifice, working in conjunction with the EVAP leak detection pump and pressure sensor. This orifice is used to establish a vacuum reference baseline for diagnosing EVAP leaks
3. EVAP leak detection pump switching valve switches from a vent position to a pump position depending on the EVAP diagnostics taking place.

Fresh Air Filter

An in-line 5 micron air filter exists between the EVAP leak detection pump fresh air intake and behind the fuel tank fill door pocket to keep the pump hardware from becoming contaminated.

Vapor Recirculation Tube

A vapor path between the fuel fill pipe and the fuel tank is necessary to fully diagnose the EVAP system. It also accommodates service diagnostic procedures by allowing the entire EVAP system to be diagnosed from the either end of the system.

2.54mm (0.100 in) Orifice in Fuel Fill Vapor Recirculation Pipe

The orifice aids refueling, onboard refueling vapor recovery (ORVR), to avoid canister overload while still allowing closed system leak detection and compliance with ORVR emissions standards.

Fuel Fill Door Lock Solenoid

Prevents fuel fill door opening prior to pressing the Refuel Request Switch.

Fuel Fill Door Position Switch

Provides input to the Hybrid Powertrain Control Module 2 to determine if the door position is open or closed.

Fuel Fill Cap

The fuel fill cap is equipped with a seal and has no relief valve.

Fuel Fill Pipe Check Valve

The check valve on the fuel fill pipe prevents spit-back during refueling.

Refuel Request Switch

Note. There is a 30 minute time frame for refueling to occur. If testing the EVAP system the vent solenoid valve will go back to it's normal closed state after 30 min.

Note. If more time is needed a second 1 second press of the switch will be required. Or use the scan tool to command the vent solenoid open, if necessary, for additional testing.

Located in the driver's door panel, this switch when pressed for 1 second, puts the EVAP diagnostics into an abort state, opens the vent solenoid valve for refueling and releases the fuel fill door. A message will be displayed on the driver information center. There is a 30 second timer on the door release mechanism allowing sufficient time to press on the fuel door to open it. If 30 seconds lapses before the fuel door is opened a second press of the refuel request switch will be required.

Fuel System Overview

The fuel system is an electronic returnless on-demand design. The returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

An electric turbine style fuel pump attaches to the fuel tank fuel pump module inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel feed pipe to the fuel injection system. The fuel tank fuel pump module contains a reverse flow check valve. The check valve maintains fuel pressure in the fuel feed pipe and the fuel rail in order to enable quick engine starts.

Electronic Returnless Fuel System

The electronic returnless fuel system is a microprocessor controlled fuel delivery system which transports fuel from the tank to the fuel rail. It functions as an electronic replacement for a traditional, mechanical fuel pressure regulator. The pressure relief regulator valve within the fuel tank provides an added measure of over-pressure protection. Desired fuel pressure is commanded by the engine control module (ECM), and transmitted to the chassis control module via a GMLAN serial data message. A fuel pressure sensor located on the fuel feed pipe provides the feedback the chassis control module requires for Closed Loop fuel pressure control.

Chassis Control Module

The chassis control module is a serviceable GMLAN module. The chassis control module receives the desired fuel pressure message from the ECM and controls the fuel pump located within the fuel tank to achieve the desired fuel pressure. The chassis control module sends a 25 kHz PWM signal to the fuel pump, and pump speed is changed by varying the duty cycle of this signal. Maximum current supplied to the fuel pump is 15 A. A fuel pressure sensor located on the fuel feed pipe provides fuel pressure feedback to the chassis control module.

Fuel Pressure Sensor

The fuel pressure sensor is a serviceable 5 V, 3-pin device. It is located on the fuel feed pipe forward of the fuel tank, and receives power and ground from the chassis control module through a vehicle wiring harness. The sensor provides a fuel pressure signal to the chassis control module, which is used to provide Closed Loop fuel pressure control.

Flex Fuel Sensor

The flex fuel sensor measures the ethanol-gasoline ratio of the fuel being used in a flexible fuel vehicle. Flexible fuel vehicles can be operated with a blend of ethanol and gasoline, up to 85 percent ethanol. In order to adjust the ignition timing and the fuel quantity to be injected, the engine management system requires information about the percentage of ethanol in the fuel.

The flex fuel sensor uses quick-connect style fuel connections, an incoming fuel connection, and an outgoing fuel connection. All fuel passes through the flex fuel sensor before continuing on to the fuel rail. The flex fuel sensor measures the fuel alcohol content, and sends an electrical signal to the engine control module (ECM) to indicate ethanol percentage.

The flex fuel sensor has a three-wire electrical harness connector. The three wires provide a ground circuit, a power source, and a signal output to the ECM. The power source is battery positive voltage and the ground circuit connects to an engine ground. The signal circuit carries the ethanol percentage via a frequency signal.

The flex fuel sensor uses a microprocessor inside the sensor to measure the ethanol percentage and changes the output signal accordingly. The ECM provides an internal pull-up to 5 V on the signal circuit, and the flex fuel sensor pulls the 5 V to ground in pulses. The normal range of operating frequency is between 50 and 150 Hz, with 50 Hz representing 0 percent ethanol, and 150 Hz representing 100 percent ethanol.

The microprocessor inside the sensor is capable of a certain amount of self-diagnosis. An output frequency between 180 Hz and 190 Hz indicates that the fuel is contaminated. Certain substances dissolved in the fuel can cause the fuel to be contaminated, raising the output frequency higher than the actual ethanol percentage should indicate. Examples of these substances include water, sodium chloride (salt), and methanol.

It should be noted that it is likely that the flex fuel sensor will indicate a slightly lower ethanol percentage than what is advertised at the fueling station. This is not a fault of the sensor. The reason has to do with government requirements for alcohol-based motor fuels. Government regulations require that alcohol intended for use as motor fuel be denatured. This means that 100 percent pure ethanol is first denatured with approximately 4 1/2 percent gasoline, before being mixed with anything else. When an ethanol gasoline mixture is advertised as E85, the 85 percent ethanol was denatured before being blended with gasoline, meaning an advertised E85 fuel contains only about 81 percent ethanol. The flex fuel sensor measures the actual percentage of ethanol in the fuel.

Fuel Tank

The fuel tank stores the fuel supply. The fuel tank is located in the rear of the vehicle. The fuel tank is held in place by 2 metal straps that are attached to the underbody. The fuel tank is molded from high-density polyethylene.

Fuel Fill Pipe

The fuel fill pipe has a built-in restrictor in order to prevent refueling with leaded fuel.

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 tightened to the proper torque and fully seated.

Fuel Tank Fuel Pump Module

The fuel tank fuel pump module consists of the following major components

1. The fuel level sensor
2. The fuel pump and reservoir assembly
3. The fuel filter
4. The pressure relief regulator valve

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.

Fuel Pump

The fuel pump is mounted in the fuel tank fuel pump module reservoir. The fuel pump is an electric turbine style pump which pumps fuel to the fuel injection system at a pressure that is based on feedback from the fuel pressure sensor. The fuel pump delivers a constant flow of fuel even during low fuel conditions and aggressive vehicle maneuvers. The fuel pump flex pipe acts to dampen the fuel pulses and noise generated by the fuel pump.

Pressure Relief Regulator Valve

The pressure relief regulator valve replaces the typical fuel pressure regulator used on a mechanical returnless fuel system. The pressure relief regulator valve is closed during normal vehicle operation. The pressure relief regulator valve is used to vent pressure during hot soaks and also functions as a fuel pressure regulator in the event of the chassis control module defaulting to 100 percent pulse width modulation (PWM) of the fuel pump. Due to variation in the fuel system pressures, the opening pressure for the pressure relief regulator valve is set higher than the pressure that is used on a mechanical returnless fuel system pressure regulator.

Nylon Fuel Pipes

Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature.

Heat resistant rubber hose or corrugated plastic conduit protects 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 Rail Assembly

The fuel rail assembly is attached to the cylinder head. The fuel rail assembly performs the following functions

1. Positions the injectors in the intake ports of the cylinder head
2. Distributes fuel evenly to the injectors

Scheme 54

The fuel injector assembly is a solenoid device controlled by the ECM that meters pressurized fuel to a single engine cylinder. The ECM energizes the high-impedance, 12 ohms, injector solenoid (4) to open a normally closed ball valve (1). This allows fuel to flow into the top of the injector, past the ball valve, and through a director plate (3) at the injector outlet. The director plate has machined holes that control the fuel flow, generating a spray of finely atomized fuel at the injector tip (2). Fuel from the injector tip is directed at the intake valve, causing the fuel to become further atomized and vaporized before entering the combustion chamber. This fine atomization improves fuel economy and emissions.

Secondary Air Injection System Description

The Secondary Air Injection System aids in the reduction of hydrocarbon exhaust emissions during a cold start. This occurs when the start-up engine coolant temperature (ECT) is between -12 and +38°C (10-100°F), the intake air temperature (IAT) is greater than -12°C (+10°F) and it has been more than 10 s since the last start. The secondary air injection pump operates 5-60 s after start-up.

The engine control module (ECM) activates the secondary air injection system by simultaneously completing the ground paths for the secondary air injection pump and the secondary air injection shutoff and check (solenoid) valve relay. This action closes the relays' internal contacts. The pump and shutoff and check valve are in turn energized. The pump turns ON and the valve opens.

The secondary air injection pump sends pressurized fresh air into the pipes/hoses, through the open shutoff and check valve and into the exhaust manifold. The extra air accelerates the catalyst operation, helping it to reach operating temperature faster. The secondary air injection pump remains ON for a short period of time after the shutoff and check valve is commanded OFF. When the pump is commanded OFF it will not run or be activated until the next vehicle cold start. When the secondary air injection system is inactive, the shutoff and check valve is closed to prevent air/exhaust flow in either direction.

The ECM monitors the secondary air injection system pressure by tracking the voltage signal which is provided by pressure sensor in the exhaust.

The ECM utilizes a 3 phase diagnostic routine to test the secondary air injection system

During phase 1, DTCs P0411 and P2430 run and both the secondary air injection pump and the shutoff and check valve is activated. Normal secondary air function occurs. Expected system pressure is 6-14 kPa (0.9-2.0 psi) above BARO.

During phase 2, DTCs P2430 and P2440 run and only the secondary air injection pump is activated. The shutoff and check valve is closed. Pressure sensor performance and shutoff and check valve deactivation are tested. Expected system pressure is 22-30 kPa (3.2-4.4 psi) above BARO.

During phase 3, DTC P2444 runs and neither the secondary air injection pump nor the shutoff and check valve is activated. Secondary air injection pump deactivation is tested. Expected system pressure equals BARO.

The secondary air injection system includes the following components

1. The secondary air injection pump-The electric secondary air injection pump supplies pressurized, filtered air to the secondary air injection shutoff and check valve. The secondary air injection pump is a turbine type pump that is permanently lubricated and requires no periodic maintenance.
2. The secondary air injection shutoff and check valve assembliy-The shutoff and check valve assembly have direct current (DC) motor operated valves. When the valve motor is energized by the secondary air injection shutoff and check (solenoid) valve relay, the valve opens, pressurized air from the secondary air injection pump flows through the valve and is directed into the exhaust manifold.
3. The secondary air injection pressure sensor-The pressure sensor is integral to the secondary air injection shutoff and check valve assembly. The sensor is a 3-wire sensor that measures the secondary air injection system pressure at the inlet of the shutoff and check valve assembly.
4. The secondary air injection pump relay-The relay supplies high current and battery voltage to the secondary air injection pump. The ECM commands the relay ON by supplying a ground to the relay control circuit.
5. The secondary air injection shutoff and check (solenoid) valve relay-The relay supplies high current and battery voltage to the secondary air injection shutoff and check valve. The ECM commands the relay ON by supplying a ground to the relay control circuit.
6. The pipes and hoses-The secondary air injection pump inlet hose carries filtered air from the engine intake air cleaner to the secondary air injection pump inlet. The secondary air injection pump pipe carries the air from the pump outlet to the shutoff and check valve which in turn feeds the exhaust manifold.

System Fault Detection

The ECM monitors the secondary air injection system for faults during cold start operation. When the system's pressure or relay circuits operations vary too far from the expected values, a DTC will set. Diagnostics detect the following conditions

1. A partially or fully blocked or leaking secondary air injection system
2. A malfunctioning secondary air injection pump
3. A malfunctioning secondary air injection shutoff and check valve assembly
4. A malfunctioning secondary air injection pressure sensor
5. A restricted exhaust system
6. A malfunctioning secondary air injection pump and secondary air injection valve relay

The following DTCs set when a secondary air injection system fault is detected

1. DTC P0411-A secondary air injection system insufficient airflow fault condition has been detected.
2. DTC P0412-A secondary air injection valve relay coil circuit fault condition has been detected.
3. DTC P0418-A secondary air injection pump relay coil circuit fault condition has been detected.
4. DTC P2430-A secondary air injection pressure sensor signal stuck in range fault condition has been detected.
5. DTC P2431-A skewed air injection pressure sensor signal has been detected.
6. DTC P2432-A secondary air injection pressure sensor signal voltage below the minimum range of the sensor fault condition has been detected.
7. DTC P2433-A secondary air injection pressure sensor signal voltage is above the maximum range of the sensor fault condition has been detected.
8. DTC P2440-The shutoff and check valve is stuck open or a system leak between the pump and the valve has been detected.
9. DTC P2444-A secondary air injection pump stuck ON fault condition has been detected.

Scheme 55

Circuit/System Description

The system torque coordination is provided by the hybrid powertrain control module. The engine control module (ECM) provides the accelerator pedal interface in which the driver requests a vehicle torque. These driver requests are coordinated and arbitrated within the ECM and the final driver requested torque is sent to the hybrid powertrain control module. The hybrid powertrain control module then determines how the torque output will be distributed between the two electric motors and the engine. After the torque distribution has been determined, torque reductions are imposed based upon system interrupts that are listed below

1. Vehicle stability
2. Torque security
3. Component overheating protection

The final arbitrated values are distributed to the system. Torque coordination of the system depends directly upon the high voltage battery pack state of charge.

This system is a distributed control system where the system torque is controlled over a system network. The system network consists of serial data communications between the controllers listed below

1. Engine control module (ECM)
2. Hybrid powertrain control module 1 and 2 (HPCM 1 and 2)
3. Transmission control module (TCM)
4. Electronic brake control module (EBCM)
5. Accessory Power Module (APM)

The hybrid powertrain control module determines the engine speed which is based on the high voltage battery pack state of charge. The ECM achieves throttle positioning by providing a pulse width modulated voltage to the throttle actuator motor. The throttle blade is spring loaded in both directions, and the default position is slightly open.

Modes Of Operation

Normal Mode

During the operation of the TAC system, several modes, or functions, are considered normal. The following modes may be entered during normal operations

1. Minimum pedal value-At Vehicle ON, the ECM updates the learned minimum pedal value.
2. Minimum throttle position values-At Vehicle ON, the ECM updates the learned minimum throttle position value. In order to learn the minimum throttle position value, the throttle blade is moved to the closed position.
3. Ice break mode-If the throttle blade is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the ECM commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
4. Battery saver mode-After a predetermined time without engine speed, the ECM commands the battery saver mode. During the battery saver mode, the ECM disables the TAC motor control circuits, which removes the current draw used to maintain the engine speed and allows the throttle to return to the spring loaded default position.

Reduced Power Mode

When the ECM detects a condition with the TAC system, the ECM may enter a propulsion power reduced mode. Propulsion power reduced mode may cause one or more of the following conditions

1. Acceleration limiting-The ECM will continue to use the accelerator pedal for propulsion control, however, the vehicle acceleration is limited.
2. Limited throttle mode-The ECM will continue to use the accelerator pedal for propulsion control, however, the propulsion power is reduced.
3. Throttle default mode-The ECM will turn OFF the throttle actuator motor, and the throttle will return to the spring loaded default position.
4. Forced idle mode-The ECM will ignore the accelerator pedal input.
5. Engine shutdown mode-The ECM will disable fuel and de-energize the throttle actuator.