Engine Controls - Theory & Operation: Other Hyundai Accent II рестайлинг

AIR INDUCTION SYSTEM

All engines use the same basic air induction system. Remote air filter (with airflow sensor) is ducted to a plenum-mounted throttle body.

COMPUTERIZED ENGINE CONTROLS

Note. Engine Control Module (ECM) may also be referred to as Powertrain Control Module (PCM).

All models use a Multiport Fuel Injection (MFI) system. MFI system consists of sensors which detect engine conditions. The ECM controls the system based on signals from these sensor and from actuators which operate under the control of the ECM. ECM controls fuel injection, idle speed, ignition timing, emission controls and other functions. ECM is equipped with several diagnostic test modes which simplify troubleshooting when a problem occurs.

ENGINE CONTROL MODULE

The ECM, through various input sensors, monitors cranking signal, intake air amount, intake air temperature, air/fuel ratio, throttle valve opening angle, No. 1 piston compression stroke TDC, engine coolant temperature, engine RPM, A/C operation, detonation, gear status (if automatic transmission/transaxle) and fuel tank pressure. ECM uses this information to control fuel injection timing and duration, ignition timing, idle speed, A/C cutout, fuel pump, purge control system and performs self-diagnostic functions.

ECM includes On Board Diagnostics-II (OBD-II) to monitor efficiency of emissions-related components and systems. If an emissions-related system malfunctions or deteriorates below preprogrammed performance criteria, OBD-II will illuminate the Malfunction Indicator Light (MIL) and store a Diagnostic Trouble Code (DTC). If a condition exists that may cause catalytic converter damage, MIL will flash continuously.

Fuel Injection Control

The ECM controls fuel injector timing and pulse width based on sensor inputs. ECM uses the Crankshaft Position (CKP) sensor to determine when to pulse each injector. ECM uses engine coolant temperature, intake air temperature, airflow and throttle position information to calculate injector pulse width. Each fuel injector is pulsed once for each cylinder for every 2 crankshaft rotations. During cranking, all injectors are pulsed simultaneously until engine starts. During engine operation, each injector is sequentially pulsed.

Engine Idle Speed Control (ISC)

The ECM controls idle speed based on engine load and temperature. Engine idle speed is kept at the optimum speed by controlling amount of air that by-passes throttle valve. ECM commands ISC actuator to keep the engine running at a pre-set idle target speed in accordance with the engine temperature and power steering (if equipped) and air conditioning loads. When engine load increases because of power steering and/or air conditioning activation, the ECM will increase engine idle speed to avoid fluctuations in engine speed.

Ignition Timing Control

The ignition power transistor, located in the ignition primary circuit, turns on and off to control the primary current flow to the ignition coil. This controls the ignition timing in order to provide the optimum ignition timing with respect to the engine operating conditions. The ignition timing is determined by the ECM from engine speed, intake air volume, engine coolant temperature and atmospheric pressure inputs.

Other Control Functions

The ECM controls the fuel pump relay, A/C compressor clutch operation, radiator and condenser fan speeds, evaporative emission purge control and EGR solenoid operation.

Note. Components are grouped into 2 categories. First category is INPUT DEVICES , which are components that control or produce signals monitored by the ECM. The second category is OUTPUT SIGNALS , which are components controlled by the ECM.

INPUT DEVICES

The ECM controls various output devices based upon signals received from input devices. These devices include sensors, switches, and circuits (such as an RPM reference signal from the ignition coil). Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine input usage on a specific model, see appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. Available input signals include the following

A/C Switch

When air conditioner switch is turned on, a signal is sent to the ECM. The ECM then engages the compressor clutch and adjusts the Idle Speed Control (ISC) actuator to maintain optimum idle speed.

Acceleration Sensor (Accent)

Acceleration sensor is located on bracket on right front strut tower, when accelerating or driving on a rough road, ECM uses the accelerator sensor input signal to avoid false misfire detection.

Camshaft Position Sensor

The Camshaft Position (CMP) sensor senses the TDC point of cylinder No. 1 in its compression stroke. This signal is fed to the ECM to determine fuel injector sequence starting point. See CAMSHAFT POSITION SENSOR LOCATIONS table.

CAMSHAFT POSITION SENSOR LOCATIONS

Crankshaft Position Sensor

The Crankshaft Position (CKP) sensor is located at the left side of the block, near the flywheel on Santa Fe and Tiburon 2.7L. On all other models, CKP is located next to crankshaft pulley. The ECM uses voltage signal from the CKP sensor to detect engine RPM and crankshaft position.

Engine Coolant Temperature Sensor

The Engine Coolant Temperature (ECT) sensor is located on thermostat housing. The ECT sensor is a thermistor whose resistance decreases as engine coolant temperature increases. The ECM uses ECT sensor information for controlling fuel enrichment when engine is cold.

Fuel Tank Pressure Sensor

On Accent, the Fuel Tank Pressure (FTP) sensor is located on fuel filler neck. On all other models, the FTP sensor is located between the fuel tank and rear suspension crossmember. The FTP sensor is a pressure-sensitive variable resistor. It measures fuel tank pressure changes, monitoring fuel tank for leaks. Canister Close Valve (CCV) is used to close the evaporative system, and observes tank pressure.

Heated Oxygen Sensor

All vehicles with 4-Cylinder engines are equipped with 2 Heated Oxygen Sensors(HO2S). All vehicles with V6 engines are equipped with 4 HO2S, one pair for each bank. On all models, a front HO2S is located in the exhaust manifold in front of the catalytic converter. The front HO2S determines whether the air fuel mixture is too rich or too lean. ECM uses front HO2S to control air fuel mixture and fuel delivery time. A rear HO2S is located after the catalytic converter. ECM compares signals from both sensors and calculates catalytic converter efficiency. On all models except Santa Fe 2.7L, Sonata 2.7L and Tiburon 2.7L, HO2S output voltage ranges from 0-0.1 volt (lean) to about 0.8-1.0 volt (rich). On Santa Fe 2.7L, Sonata 2.7L and Tiburon 2.7L, HO2S output voltage ranges from 0-0.2 volt (lean) to about 4.5-5.0 volts (rich). HO2S heater is used to bring sensor to operating temperature as quickly as possible for optimum operation under all engine operating conditions.

Idle Position Switch (Sante Fe 3.5L & XG350)

Note. Idle position switch may also be referred to as idle switch.

The Idle switch is built into the Throttle Position (TP) sensor as one single component. The idle switch signals the ECM whether accelerator pedal is depressed or not. The Idle switch is normally closed at idle and open when accelerator is off idle position.

Intake Air Temperature Sensor

The Intake Air Temperature (IAT) sensor measures temperature of intake air, and sends a signal to the ECM. The IAT sensor is a variable-resistor type airflow sensor. As intake air temperature decreases, IAT sensor output voltage to ECM increases. On Accent, Elantra and Tiburon 2.0L, the IAT sensor is combined with the Manifold Absolute Pressure (MAP) sensor and is located in the air intake plenum. On Santa Fe 2.4L and 3.5L, Sonata 2.4L and XG350, the IAT sensor is combined with the Mass Air Flow (MAF) sensor and is located in the air intake hose. On Santa Fe 2.7L, Sonata 2.7L and Tiburon 2.7L, the IAT sensor is located in air intake plenum. The ECM uses the IAT sensor signal to control fuel delivery. When air temperature is cold, the ECM enriches fuel mixture by increasing injector pulse width. The ECM will decrease injector pulse width as air temperature warms.

Knock Sensor

The Knock Sensor (KS) is mounted on engine block. The KS detects knocking condition/vibration from engine. The KS is a piezo electric element that converts vibration into a voltage signal which is then sent to the ECM. On Accent, the ECM compares KS and rough road (acceleration) sensor inputs to detect true engine knock. See ACCELERATION SENSOR (ACCENT) . If the ECM determines that engine knock is occurring, the ECM will retard timing until knock is suppressed.

Mass Airflow Sensor

The Mass Airflow (MAF) sensor is a hot-film type airflow sensor mounted within the intake duct between the air cleaner and throttle body. MAF rate is measured by detecting changes in the temperature of the hot-film probe, and comparing it to changes in sensor resistance. ECM uses MAF signal to determine basic fuel injection pulse width and ignition timing.

Manifold Absolute Pressure Sensor (Accent, Elantra, Santa Fe 2.4L, Sonata 2.4L, Tiburon 2.0L & XG350)

The Manifold Absolute Pressure (MAP) sensor converts intake manifold pressure into a voltage signal. The ECM uses MAP sensor signal to verify operation of EGR system.

Power Steering Pressure Switch (Santa Fe, Sonata 2.4L, Sonata 2.7L, Tiburon 2.7L & XG350)

The Power Steering Pressure (PSP) switch closes in response to an increase in power steering fluid pressure (load condition). With the switch closed, a monitored voltage circuit supplied by the ECM is pulled low to vehicle ground through switch. The ECM then sends a signal to the Idle Speed Control (ISC) actuator to adjust idle speed to compensate for increased engine load.

Throttle Position Sensor

The Throttle Position (TP) sensor is a potentiometer connected to the throttle valve shaft. As throttle opening changes, the sensor sends a voltage signal to the ECM. The ECM uses this signal to calculate fuel injection duration.

Transaxle Range Switch (A/T)

The Transaxle Range (TR) switch informs the ECM when the transaxle is in Neutral or Park. ECM determines automatic transmission load, and signals the Idle Air Control (IAC) valve to maintain optimum idle speed.

Vehicle Speed Sensor

The Vehicle Speed Sensor (VSS) is located within the speedometer assembly, and uses a reed switch to sense speedometer gear revolutions from the transaxle. The VSS converts transaxle gear revolutions into pulse signals which are sent to the ECM.

OUTPUT SIGNALS

Note. Vehicles are equipped with different combinations of computer-controlled components. Not all components listed are used on every vehicle. For theory and operation on each output component, refer to system indicated after component.

The ECM processes information from input sensors and sends appropriate control signals to the following engine controls

A/C Clutch

See A/C CLUTCH under MISCELLANEOUS CONTROLS.

A/C Condenser Fan Relay

See appropriate article in MANUAL A/C-HEATER SYSTEMS.

Blower Motor Relay

See appropriate article in HEATER SYSTEMS (without A/C) or MANUAL A/C-HEATER SYSTEMS (with A/C).

EVAP Canister Close Valve

See EVAP CANISTER CLOSE VALVE under EVAPORATIVE & ON-BOARD REFUELING VAPOR RECOVERY EMISSION CONTROL SYSTEM.

EVAP Purge Control Solenoid Valve

See EVAP CANISTER PURGE CONTROL SOLENOID VALVE under EVAPORATIVE & ON-BOARD REFUELING VAPOR RECOVERY EMISSION CONTROL SYSTEM.

EGR Control Solenoid Valve

See EXHAUST GAS RECIRCULATION CONTROL under EMISSION SYSTEMS.

Engine Control Relay

See RELAYS in SYSTEM & COMPONENT TESTING article.

Fuel Injectors

See FUEL INJECTORS under FUEL CONTROL.

Fuel Pump Relay

See FUEL PUMP RELAY under FUEL DELIVERY.

Idle Speed Control Actuator

See IDLE SPEED CONTROL ACTUATOR under IDLE SPEED.

Malfunction Indicator Light

See MALFUNCTION INDICATOR LIGHT under SELF-DIAGNOSTIC SYSTEM.

FUEL DELIVERY

Fuel is sent under pressure from the fuel tank by the fuel pump, and the pressure is regulated by the fuel pressure regulator positioned downstream of the injectors.

Fuel Pump

Located within the fuel tank, the fuel pump consists of an impeller driven by a DC motor. The pump has an internal check valve (to maintain system pressure) and a relief valve (to relieve excessive pressure).

Fuel Pressure Regulator

On Accent, Elantra and Tiburon 2.0L, the fuel pressure regulator is a located in the fuel pump. On all other models, the fuel pressure regulator is located on the fuel delivery pipe. The fuel pressure regulator maintains a constant pressure at the injectors during all engine operating conditions.

The fuel pump relay can be found by itself or combined in the ECM relay. This multipurpose relay switches power to the MAF and VAF sensors, ISC motor, injectors, and fuel pump. For specific system configuration, see appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. For fuel pump and ECM relay location, see FUEL PUMP & ECM RELAY LOCATIONS table.

FUEL PUMP & ECM RELAY LOCATIONS

Fuel Injection Control System

The injector drive times and injector timing are controlled so that optimum air/fuel mixture is supplied to engine. Fuel is sent under pressure from the fuel tank by the fuel pump. Fuel pressure is regulated by the fuel pressure regulator. The regulated fuel is distributed to each of the Multiport Fuel Injection (MFI) injectors. Fuel injection is normally carried out once for each cylinder for every two rotations of the crankshaft. The ECM provides a richer air/fuel mixture by carrying out "open-loop" control when the engine is cold or operating under high load conditions in order to maintain engine performance. In addition, when the engine is warm or operating under normal conditions, the ECM controls the air/fuel mixture by using the heated oxygen sensor signal to carry out "closed-loop" control in order to obtain the theoretical air/fuel mixture ratio that provides the maximum cleaning performance from the 3-way catalytic converter.

Fuel is supplied to engine through electronically-pulsed (timed) fuel injectors. The ECM controls amount of fuel metered through injectors based on information received from various sensors. A single fuel injector is mounted at the intake port of each cylinder.

Idle Speed Control System

The idle speed is kept at the optimum speed, by controlling the amount of air that bypasses the throttle valve in accordance with changes in idling conditions and engine load during idling. The ECM drives the Idle Speed Control (ISC) actuator to keep the engine running at the pre-set idle target speed in accordance with the engine coolant temperature and air conditioning load. In addition, when the air conditioning switch is turned off and on while the engine is idling, the ISC actuator operates to adjust the throttle valve bypass air amount in accordance with the engine load conditions in order to avoid fluctuations in the engine speed.

The Idle Speed Control (ISC) actuator is a double-coil type. The 2 coils are driven by separate driver stages in the ECM. Depending on the pulse duty factor, the balance between the magnetic forces of the 2 coils will result in different angles of the motor. The actuator is located in by-pass hose to throttle body.

DIRECT IGNITION

The Direct Ignition System (DIS) is a molded, dual-coil system. The system does not use a distributor. Ignition timing is controlled by the electronic control ignition timing system. The ignition timing curves for the engine operating conditions are programmed into the memory of the ECM.

The engine conditions (speed, load, warm-up condition, etc.) are detected by the various sensors. Based upon these sensor signals and the ignition timing curve data, signals to interrupt the primary current are sent, ignition coil is activated, and timing is controlled at the optimum point.

IGNITION TIMING CONTROL SYSTEM

The ignition power transistor located in the ignition primary circuit turns ON and OFF to control the primary current flow to the ignition coil. This controls ignition timing in order to provide the optimum ignition timing with respect to the engine operating conditions. The ignition timing is determined by the ECM from engine speed, intake air volume, engine coolant temperature and atmospheric pressure.

Santa Fe & XG350

The ECM controls Exhaust Gas Recirculation (EGR) operation by activating the EGR control solenoid valve according to engine load. When engine is cold, the ECM signals the EGR control solenoid valve to deactivate EGR. The ECM verifies EGR operation by monitoring the Manifold Absolute Pressure (MAP) sensor signal for a change in pressure when EGR is requested. EGR flow will result in a change in the MAP sensor signal. If signal does not change as expected, the ECM will recognize this as an EGR malfunction, and will store a Diagnostic Trouble Code (DTC) and turn on the Malfunction Indicator Light (MIL).

EVAPORATIVE & ON-BOARD REFUELING VAPOR RECOVERY EMISSION CONTROL SYSTEM

The Evaporative (EVAP) and On-board Refueling Vapor Recovery (ORVR) system consists of a fill vent valve, fuel shut-off valve, fuel cut (roll-over) valve, fuel liquid/vapor separator, EVAP canister, EVAP Canister Purge Control Solenoid Valve (CPCSV), EVAP Canister Close Valve (CCV), vacuum relief filler cap and connecting lines and hoses. ORVR system is designed to prevent the release of fuel vapors during refueling. During refueling, as fuel enters the fuel tank, a vacuum is created in filler pipe, drawing air into the filler pipe and tank. Fuel vapor in fuel tank is then forced to the EVAP canister via the fill vent valve and the fuel liquid/vapor separator. A Fuel Tank Pressure (FTP) sensor is used for detecting EVAP system leaks by comparing pressures inside and outside of fuel tank.

Evaporative Canister

Filled with activated charcoal, canister stores fuel vapors to be burned or returned to fuel tank.

EVAP Canister Purge Control Solenoid Valve

Fuel vapors are vented into the EVAP canister during refueling and when ignition is off. When engine is at normal operating temperature and engine speed is greater than idle, a thermovalve opens and allows vacuum to open the purge control valve. Canister vapors are then drawn into the intake manifold for burning during combustion. The EVAP Canister Purge Control Solenoid Valve (CPCSV) is kept closed during idle and engine warm-up to reduce HC and CO emissions.

EVAP Canister Close Valve (CCV) is located on the charcoal canister, and is used to seal charcoal canister vent during on-board diagnosis of EVAP system. CCV is controlled by the ECM, normally remains open and is not used for normal EVAP system operation.

POSITIVE CRANKCASE VENTILATION VALVE

The system consists of a Positive Crankcase Ventilation (PCV) valve and ventilation hoses. The PCV valve is located on the valve cover. When the engine is running, manifold vacuum pulls the PCV valve back, allowing crankcase fumes to enter intake manifold through a restricted orifice. As throttle opens, manifold vacuum drops, allowing PCV valve spring pressure to open PCV valve. This will increase volume of flow through valve to accommodate increase in crankcase blow-by gases. If the engine backfires through intake manifold, the PCV valve will be forced closed, preventing crankcase combustion.

The MIL illuminates to notify the driver that there is a problem with the vehicle. However the MIL will go off automatically after 3 subsequent sequential driving cycles if the same malfunction is not being redetected. Immediately after the ignition switch is turned on, the MIL is illuminated for 5 seconds to indicate that the light is operating normally. The following systems or components, when malfunctioning, can be indicated by the MIL

1. Mass Airflow (MAF) sensor.
2. Camshaft Position (CMP) sensor.
3. Catalytic Converter.
4. Crankshaft Position (CKP) sensor.
5. Engine Coolant Temperature (ECT) sensor.
6. Evaporative (EVAP) Emission Control System.
7. Fuel Injectors.
8. Fuel system.
9. Front and rear Heated Oxygen Sensor (HO2S).
10. Front and rear HO2S heater.
11. Idle Speed Control (ISC) actuator.
12. Intake Air Temperature (IAT) sensor.
13. Misfire.
14. Throttle Position (TP) sensor.
15. Vehicle Speed Sensor (VSS).

MISCELLANEOUS CONTROLS

Note. Although not considered true engine performance-related systems, controlled devices may affect driveability if they malfunction.

When the A/C is turned on while engine is at idle, Idle Air Control (IAC) actuator will increase engine idle speed. To prevent the A/C compressor clutch from switching on before idle speed has increased, the Engine Control Module (ECM) briefly opens the A/C relay circuit.

Engine Control Module (ECM) turns fuel pump relay ON so that current is supplied to the fuel pump while engine is cranking or running.

RADIATOR COOLING FAN

The radiator fan and condenser fan speeds are controlled by Engine Control Module (ECM) in response to the engine coolant temperature and vehicle speed.

TRANSAXLE CONTROL

Some automatic transaxle models are equipped with an electronic Transmission Control Module (TCM). TCM receives input signals from ignition coil (RPM signal), idle switch (on-off signal), TP sensor (variable signal) and full throttle switch (on-off signal). Based on these values, TCM calculates optimum timing and duration to energize shift solenoids, overrun clutch solenoid and lock-up solenoid.