Underhood Emission Control Components

Component Descriptions

Component	Function	Remark
A／C relay	Controls A／C operation according to vehicle conditions and sends A／C operation condition signals to ECM	Controls condenser fan operation
A／C switch	Controls battery power to A／C relay	Normally open type
Air cleaner	Filters air entering throttle body	Dry type
Camshaft position(CMP) sensor	Detects No. 1 cylinder TDC; sends signal to ECM	Installed at rear of cylinder head
Data link connector (DLC)	Centralized sevice connector for on-board diagnosis	For on board diagnosis and service／inspection
EGI main relay	Supplies battery power to electrical devices	1. Normally open type 2. Controlled by ECM
EGR differential pressure sensor	Detects EGR pressure or barometric pressure and send signal to ECM	For EGR check control
EGR solenoid valve	Controls vacuum or barometric pressure to EGR valve	1. Duty controlled 2. Actuated by EGR control signal of ECM
EGR valve	Controls exhaust gas flow from exhaust manifold to intake manfiold (dynamic chamber)	Actuated by EGR solenoid valve
Engine control module(ECM)	Detects the following : 1. A／C operation 2. Air／fuel ratio(oxygen conecntration) 3. Cranking signal 4. Engine coolant temperature 5. Engine speed 6. Ignition ON signal 7. In-gear condition 8. Intake air amount 9. No. 1 piston TDC(compression stroke) 10. Throttle valve opening angle Controls operation of following : 1. A／C(cut-off) 2. Self-diagnosis funtion 3. Fuel injection system 4. Idle speed control 5. Monitor fountion 6. Purge control system 7. EGR funtion control system 8. Fuel pump control	1. Air conditioning switch 2. Oxygen sensor 3. Ignition switch 4. Engine coolant temperature sensor 5. Crankshaft position(CKP) sensor(SGT) 6. Ignition switch 7. Transmission range switch(A／T) 8. Mass air flow sensor 9. Camshaft position(CMP) sensor(SGC signal) 10. Trottle position sensor 1. A／C cut-off relay 2. Self-diagnosis checker&MIL 3. Injector 4. Idle air control valve 5. Monitor lamp 6. Purge solenoid valve 7. EGR solenion valve 8. Fuel pump relay
Engine coolant temperature(ECT) sensor	Detects engine coolant temperature and sends signals to ECM	Installed near thermostat
Evaporative emission canister	Stores fuel tank vapors(engine stopped)	―
Fuel filter (high pressure side)	Filters fine dirt particles in fuel discharged from the fuel pump	―
Fuel filter(low pressure side)	Filters fuel in fuel tank	Installed onto pump assembly
Fuel pressure regulator	Adjusts fuel pressure supply to injectors
Fuel pump	Supplies fuel from fuel tank to injectors under pressure	Actuated by fuel pump relay Installed in fuel tank
Fuel pump relay	Controls battery power to fuel pump	1. Normally open type 2. Actuated by ECM fuel pump control signal or by jumping data link connector terminal ＃1 to B＋
Heated oxygen sensor(rear)	Detector oxygen density in exhaust gas and sends signal to ECM	1. Located downstream of catalytic converter 2. For catalytic converter effciency evaluation
Idle air control(IAC) valve	Supples intake air to engine, bypassing the throttle valve	1. For idle speed control 2. Actuated by ECM idle speed control signal
Ignition coils	Supplies seconary voltage to spark plugs	Mounted directly
Ignition control module	Controls operation of ignition coils	Incorporated into ECM
Ignition switch	Starts engine and controls battery power to electrical device and ECM
Intake manifold	Supplies intake air to all cylinders
Knock sensor	Detects detonation in the combustion chamber(s) and sends signal to ECM	The ECM will retard ignition timing based on input signal
Main relay	Supplies current to output device and ECM
Mass air flow(MAF) sensor	Detests amount of intake air and send signal to ECM	Hot film type
Positive crankcase ventilation(PCV)	Sends blow-by gas in crankcase into intake manifold(dynamic chamber)	1. Actuated by intake manifold vacuum 2. For blow-by gas recirculation
Pressure regulator	Adjusts fuel pressure according to intake manifold
Purge solenoid valve	Controls fuel vapor from charcal canister to intake manifold(dynamic chamber)	1. For purge control 2. Actuated by ECM purge control signal
Resonance chamber	Reduces intake air suction noise and increases engine torque
Three way cataytic converter	Reduces HC, CO, and NOx in exhaust gas by chemical reastion	For exhaust gas emissions reduction
Throttle body	Controls intake air amount
Throttle positive sensor	Detects throttle valve opening angle; sends signal to ECM	Installed on throttle body
Two way check valve	Supplies fuel vapor to charcoal canister when pressure in fuel tank is positive. Supplies freash air to fuel tank when pressure is negative.	1. For idle speed control 2. Load／no-load determination
Vehicle speed sensor	Detects vehicle speed signal from speedometer and sends signal to ECM

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