Fuel and Emissions System Description

Electronic Control System


The functions of the fuel and emission control systems are managed by the powertrain control module (PCM).

Fail-safe Function

When an abnormality occurs in a signal from a sensor, the PCM ignores that signal and assumes a pre-programmed value for that sensor that allows the engine to continue to run.

Back-up Function

When an abnormality occurs in the PCM, the injectors are controlled by a back-up circuit independent of the system to permit minimal driving.

Self-diagnosis

When an abnormality occurs in the signal from a sensor, the PCM supplies ground for the malfunction indicator lamp (MIL) and stores the diagnostic trouble code (DTC) in erasable memory. When the ignition is first turned on, the PCM supplies ground for the MIL for 2 seconds to check the MIL bulb condition.

Two Driving Cycle Detection Method

To prevent false indications, the ‘‘two driving cycle detection method'' is used for some self-diagnostic functions. When an abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON (II) again, the PCM informs the driver by turning on the MIL.

PCM Data


You can retrieve data from the PCM by connecting the HDS or the scan tool to the Data Link Connector (DLC). The items listed in the table below conform to SAE recommended practice. The HDS also reads data beyond that recommended by SAE so that this data may help you find the causes of intermittent problems.

NOTE:

Data Description Operating Value Freeze Data 
Diagnostic Trouble Code (DTC) If the PCM detects a problem, it will store it as a code consisting of one letter and four numbers. Depending on the problem, an SAE-defined code (P0xxx) or a Honda-defined code (P1xxx) will be output to the tester. If no problem is detected, there is no output. YES 
Engine Speed The PCM computes engine speed from the signals sent from the Crankshaft Position (CKP) sensor. This data is used for determining the time and amount of injected fuel. Nearly the same as tachometer indication
At idle speed:
L13A4 engine:
750±50 rpm (min-1
YES 
Vehicle Speed The PCM converts pulse signals from the Vehicle Speed Sensor (VSS). Nearly the same as speedometer indication YES 
Manifold Absolute Pressure (MAP) The absolute pressure caused in the intake manifold by engine load and speed. With engine stopped: Nearly the same as atmospheric pressure
At idle speed: about 20-34 kPa (150-260 mmHg, 6-10 in.Hg), 0.7-1.1 V 
YES 
Engine Coolant Temperature (ECT) The ECT sensor converts coolant temperature into voltage and signals the PCM. The sensor is a thermistor whose internal resistance changes with coolant temperature. The PCM uses the voltage signals from the ECT sensor to determine the amount of injected fuel. With cold engine: Same as ambient temperature and IAT
With engine warmed up: about 80-100°C (176-212°F), 0.5-0.8 V 
YES 
Primary Heated Oxygen Sensor (Primary HO2S), (Sensor 1) Secondary Heated Oxygen Sensor (Secondary HO2S) (Sensor 2) The HO2S detects the oxygen content in the exhaust gas and sends voltage signals to the PCM. Based on these signals, the PCM controls the air fuel ratio. When the oxygen content is high (that is, when the ratio is leaner than the stoichiometric ratio), the voltage signal is lower. When the oxygen content is low (that is, when the radio is richer than the stoichiometric ratio), the voltage signal is higher. 0.0-1.25 V
At idle speed:
about 0.1-0.9 V 
NO 

Data Description Operating Value Freeze Data 
Fuel System Status Fuel system status is indicated as ''open'' or ''closed''.
Closed: Based on the A/F sensor and HO2S output, the PCM determines the air/fuel ratio and controls the amount of injected fuel.
Open: ignoring the A/F sensor and HO2S output, the PCM refers to signals from the throttle position (TP), manifold absolute pressure (MAP), intake air temperature (IAT), barometric pressure (BARO) and engine coolant temperature (ECT) sensors to control the amount of injected fuel. 
At idle speed: closed YES 
Short Term Fuel Trim The air/fuel ratio correction coefficient for correcting the amount of injected fuel when the Fuel System Status is ''closed.'' When the ratio is leaner than the stoichiometric ratio, the PCM increases short term fuel trim gradually, and the amount of injected fuel increases. The air/fuel ratio gradually gets richer, causing a lower oxygen content in the exhaust gas. Consequently, the short term fuel trim is lowered, and the PCM reduces the amount of injected fuel.
This cycle keeps the air/fuel ratio close to the stoichiometric ratio when in closed loop status. 
0.70-1.47 YES 
Long Term Fuel Trim Long term fuel trim is computed from short term fuel trim and indicates changes occurring in the fuel supply system over a long period.
If long term fuel trim is higher than 1.00, the amount of injected fuel must be increased. If it is lower than 1.00, the amount of injected fuel must be reduced. 
0.80-1.20 YES 
Intake Air Temperature (IAT) The IAT sensor converts intake air temperature into voltage and signals the PCM. When intake air temperature is low, the internal resistance of the sensor increases, and the voltage signal is higher. With cold engine:
Same as ambient temperature and ECT 
YES 
Throttle Position Based on the accelerator pedal position, the opening angle of the throttle valve is indicated. At idle speed:
about 10 %, 0.5 V 
YES 
Ignition Timing Ignition timing is the ignition advance angle set by the PCM. The PCM matches ignition timing to the driving conditions. At idle speed: 8° ± 5°BTDC when the SCS service signal line is jumped with the HDS NO 
Caluculated Load Valve (CLV) CLV is the engine load calculated from the MAP data. At idle speed:
12-34 %
At 2,500 rpm (min-1) with no load:
15-25 % 
YES 

PCM Inputs and Outputs at Connector A (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
BLK/WHT PO2SHTC (PRIMARY HEATED OXYGEN SENSOR (PRIMARY HO2S) HEATER CONTROL) Drives primary HO2S heater With ignition switch ON (II): battery voltage
With fully warmed up engine running: duty controlled 
YEL/BLK IGP2 (POWER SOURCE) Power source for the PCM circuit With the ignition switch ON (II): battery voltage
With the ignition switch OFF: about 0 V 
YEL/BLK IGP1 (POWER SOURCE) Power source for the PCM circuit With the ignition switch ON (II): battery voltage
With the ignition switch OFF: about 0 V 
BRN PG2 (POWER GROUND) Ground for the PCM circuit Less than 0.1 V at all times 
BLK PG1 (POWER GROUND) Ground for the PCM circuit Less than 0.1 V at all times 
WHT PHO2S (PRIMARY HEATED OXYGEN SENSOR (PRIMARY HO2S) SENSOR 1) Detects primary HO2S sensor (sensor 1) signal With throttle fully opened from idle with fully warmed up engine: about 0.6 V
With throttle quickly closed: below 0.4 V 
BLU CKP (CRANKSHAFT POSITION SENSOR) Detects CKP sensor signal With engine running: pulses 
RED/BLU KS (KNOCK SENSOR) Detects knock sensor signal With engine knocking: pulses
With ignition switch ON (II): about 0 V 
10 GRN/BLK SG2 (SENSOR GROUND) Sensor ground Less than 0.1 V at all times 
11 GRN/WHT SG1 (SENSOR GROUND) Sensor ground Less than 0.1 V at all times 
12 BLK/BLU IACV (IDLE AIR CONTROL (IAC) VALVE) Drives IAC valve With engine running: duty controlled 
13 WHT/BLK EGRP (EXHAUST GAS RECIRCULATION (EGR) VALVE POSITION SENSOR) Detects EGR valve position sensor signal With engine running: 1.2 V-2.0 V (depending on EGR valve lift) 
15 RED/BLK TPS (THROTTLE POSITION (TP) SENSOR) Detects TP sensor signal With throttle fully open: about 4.8 V
With throttle fully closed: about 0.5 V 

PCM Inputs and Outputs at Connector A (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
16 WHT/BLK IGPLS3E (No. 3 REAR IGNITION COIL PULSE) Drives No. 3 rear ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
   18*1 BLU/WHT VABS (VEHICLE SPEED SIGNAL FROM ABS) Input vehicle speed from ABS control unit Depending on vehicle speed: pulses 
19 RED/GRN MAP (MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR) Detects MAP sensor signal With ignition switch ON (II): about 3 V
At idle: about 1.0 V (depending on engine speed) 
20 YEL/BLU VCC2 (SENSOR VOLTAGE) Provides sensor voltage With ignition switch ON (II): about 5 V
With ignition switch OFF: about 0 V 
21 YEL/RED VCC1 (SENSOR VOLTAGE) Provides sensor voltage With ignition switch ON (II): about 5 V
With ignition switch OFF: about 0 V 
23 BRN/YEL LG2 (LOGIC GROUND) Ground for the PCM circuit Less than 0.1 V at all times 
24 BRN/YEL LG1 (LOGIC GROUND) Ground for the PCM circuit Less than 0.1 V at all times 
26 GRN CMP (CAMSHAFT POSITION (CMP) SENSOR (TDC (TOP DEAD CENTER (TDC) SENSOR)) Detects CMP (TDC) sensor With engine running: pulses 
27 WHT/BLU IGPLS4I (No. 4 FRONT IGNITION COIL PULSE) Drives No. 4 front ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
28 WHT/BLK IGPLS3I (No. 3 FRONT IGNITION COIL PULSE) Drives No. 3 front ignition coil 
29 WHT/GRN IGPLS2I (No. 2 FRONT IGNITION COIL PULSE) Drives No. 2 front ignition coil 
30 WHT IGPLS1I (No. 1 FRONT IGNITION COIL PULSE) Drives No. 1 front ignition coil 
*1: with ABS

PCM Inputs and Outputs at Connector B (24P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
WHT IGPLS1E (No. 1 REAR IGNITION COIL PULSE) Drives No. 1 rear ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
YEL INJ4 (No. 4 INJECTOR) Drives No. 4 injector With ignition switch ON (II): battery voltage
At idle: duty controlled 
BLU INJ3 (No. 3 INJECTOR) Drives No. 3 injector 
RED INJ2 (No. 2 INJECTOR) Drives No. 2 injector 
BRN INJ1 (No. 1 INJECTOR) Drives No. 1 injector 
GRN FANC (RADIATOR FAN CONTROL) Drives radiator fan relay With radiator fan running: about 0 V
With radiator fan stopped: battery voltage 
GRN/WHT DNLS+ (CVT DRIVEN PULLEY CONTROL VALUE+ SIDE) Drives CVT driven pulley control value With ignition switch ON (II): pulsing signal 
RED/WHT ECT (ENGINE COOLANT TEMPERATURE SENSOR) Detects ECT sensor signal With the ignition switch ON (II): about 0.1-4.8 V
(depending on engine coolant temperature) 
10 WHT/GRN IGPLS2E (No. 2 REAR IGNITION COIL PULSE Drives No. 2 rear ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
13 WHT/RED ALTF (ALTERNATOR FR SIGNAL) Detects alternator FR signal With engine running:about 0 V-5 V
(depending on electrical load) 
14 PNK EGR (EXHAUST GAS RECIRCULATION (EGR) VALVE) Drives EGR valve With EGR operating: duty controlled
With EGR not operating: about 0 V 
16 YEL SCLS+ (CVT START CLUTCH PRESSURE CONTROL VALVE + SIDE Drives CVT start clutch pressure control valve With ignition switch ON (II): pulsing signal 
17 RED/YEL IAT (INTAKE AIR TEMPERATURE SENSOR) Detects IAT sensor signal With ignition switch ON (II): about 0.1 V-4.8 V
(depending on intake air temperature) 
21 RED/YEL PCS (EVAPORATIVE EMISSION (EVAP) CANISTER PURGE VALVE) Drives EVAP canister purge valve With engine running, engine coolant below 65°C (149°F): about 0 V
With engine running, engine coolant above 65°C (149°F): duty controlled 
22 WHT/BLU IGPLS4E (No. 4 REAR IGNITION COIL PULSE Drives No. 4 rear ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
24 BLU/WHT DRLS+ (CVT DRIVE PULLEY CONTROL VALVE + SIDE) Drives CVT drive pulley control valve With ignition switch ON (II): duty controlled 

PCM Inputs and Outputs at Connector C (22P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
PNK/BLK DNLS- (CVT DRIVEN PULLEY CONTROL VALVE-SIDE Drives CVT driven pulley control valve  
BRN PG (CVT2) (POWER GROUND CVT2) Ground for the PCM circuit  
BLK PG (CVT1) (POWER GROUND CVT1) Ground for the PCM circuit  
GRN/BLK INHSOL (INHIBITOR SOLENOID CONTROL) Drives inhibitor solenoid With inhibitor solenoid ON: battery voltage
With inhibitor solenoid OFF: 0 V 
RED/BLU NDR (CVT DRIVE PULLEY SPEED SENSOR) Detects CVT drive pulley speed sensor signal With ignition switch ON (II): 0 V or 5 V 
PNK/BLU SCLS- (CVT START CLUTCH PRESSURE CONTROL VALVE B-SIDE) Drives CVT start clutch pressure control valve  
BLU/WHT ATPS (TRANSMISSION RANGE SWITCH S POSITION) Drives transmission range switch S position signal In S position: 0 V
In any other position: about 5 V or battery voltage 
10 WHT ATPR (TRANSMISSION RANGE SWITCH R POSITION) Detects transmission range switch R position signal In R position: 0 V
In any other position: about 10 V 
11 BLU ATPL (TRANSMISSION RANGE SWITCH L POSITION) Detects transmission range switch L position signal In L position: 0 V
In any other position: about 10 V 
12 LT GRN ATPNP (TRANSMISSION RANGE SWITCH NEUTRAL/PARK POSITION) Detects transmission range switch Neutral/Park position signal In Park or Neutral: 0 V
In any other position: about 10 V 
15 WHT NDN (CVT DRIVEN PULLEY SPEED SENSOR) Detects CVT driven pulley speed sensor signal With ignition switch ON (II): 0 V or 5 V 
16 GRN/YEL DRLS- (CVT DRIVE PULLEY CONTROL VALVE-SIDE) Drives CVT drive pulley control valve With ignition switch ON (II): pulses 
20 PNK ATPD (TRANSMISSION RANGE SWITCH D POSITION) Detects transmission range switch D position signal In D position: about 0 V
In any other position: about 5 V 
22 WHT/RED VEL1 (CVT SPEED SENSOR) Detects CVT speed sensor Depending on vehicle speed: pulses
When vehicle is stopped: about 0 V or about 5 V 

PCM Inputs and Outputs at Connector E (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
WHT/RED SHO2S (SECONDARY HEATED OXYGEN SENSOR (SECONDARY HO2S), SENSOR 2) Detects secondary HO2S (sensor 2) signal With throttle fully opened from idle with fully warmed up engine: above 0.6 V
With throttle quickly closed: below 0.4 V 
BRN/YEL LG3 (LOGIC GROUND) Ground for the PCM control circuit Less than 0.1 V at all times 
PNK SG3 (SENSOR GROUND) Sensor ground Less than 0.1 V at all times 
GRN/WHT FUP (FUEL INJECTION SIGNAL) Sends fuel injection signal to gauge assembly With ignition switch ON (II): pulses 
BLK/WHT SO2SHTC (SECONDARY HEATED OXYGEN SENSOR (SECONDARY HO2S) HEATER CONTROL) Drives secondary HO2S heater With ignition switch ON (II): battery voltage
With fully warmed up engine running: duty controlled 
RED/YEL MRLY(PGM-FI MAIN RELAY) Drives PGM-FI main relay 1 Power source for the DTC memory With ignition switch ON (II): about 0 V
With ignition switch OFF: battery voltage 
BLK/YEL IG1 (IGNITION SIGNAL) Detects ignition signal With ignition switch ON (II): battery voltage
With ignition switch OFF: about 0 V 
10 GRN/YEL FPR (FUEL PUMP RELAY) Drives PGM-FI main relay 2 0 V for 2 seconds after turning ignition switch ON (II), then battery voltage 
11 PNK DIND (D INDICATOR) Drives D indicator light With D indicator light turned ON: about 6 V
With D indicator light turned OFF: 0 V 
12 BLU TAC Detects evaporator sensor signal With ignition switch ON (II): about 0.1-4.8 V (depending on evaporator temperature) 
13 BLU/RED SLC (SHIFT LOCK CONTROL) Drives shift lock solenoid With ignition switch ON (II), in Park position, brake pedal pressed, and accelerator pedal released: 0 V 

PCM Inputs and Outputs at Connector E (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
18 RED ACC (A/C CLUTCH RELAY) Drives A/C clutch relay With compressor ON: about 0 V
With compressor OFF: battery voltage 
22 WHT/BLK BKSW (BRAKE PEDAL POSITION SWITCH) Detects brake pedal position switch signal With brake pedal released: about 0 V
With brake pedal pressed: battery voltage 
23 RED/WHT K-LINE Sends and receives HDS or scan tool signal With ignition switch ON (II): battery voltage 
24 GRN MTRTW Sends engine coolant temperture signal With ignition switch ON (II): pulse 
25 BLU/YEL VSSOUT (VEHICLE SPEED SENSOR (VSS) OUTPUT SIGNAL) Sends vehicle speed sensor signal Depending on vehicle speed: pulses 
26 BLU NEP (ENGINE SPEED PULSE) Outputs engine speed pulse With engine running: pulses 
28 BLU/WHT ACS (A/C SWITCH SIGNAL) Detects A/C switch signal With A/C switch ON: 0 V
With A/C switch OFF: about 5 V 
29 BRN SCS (SERVICE CHECK SIGNAL) Detects service check signal With the service check signal shorted with the HDS or the scan tool: about 0 V
With the service check signal opened: about 5 V 
30 RED/BLU WEN (WRITE ENABLE SIGNAL) Detects write enable signal With ignition switch ON (II): about 0 V 
31 GRN/ORN MIL (MALFUNCTION INDICATOR LAMP) Drives MIL With MIL turned ON: about 0 V
With MIL turned OFF: battery voltage 

Vacuum Hose Routing


 

Vacuum Distribution


 

PGM-FI System


The Programmed Fuel Injection (PGM-FI) system is a sequential multiport fuel injection system.

Air Conditioning (A/C) Compressor Clutch Relay

When the Powertrain Control Module (PCM) receives a demand for cooling from the A/C system, it delays the compressor from being energized, and enriches the mixture to assure smooth transition to the A/C mode.

Alternator Control

The alternator signals the PCM during charging.

Barometric Pressure (BARO) Sensor

The BARO sensor is inside the PCM. It converts atmospheric pressure into a voltage signal that the PCM use to modify the basic duration of the fuel injection discharge.

Camshaft Position (CMP) Sensor
(Top Dead Center (TDC) Sensor)

The CMP (TDC) sensor detects the position of the No. 1 cylinder as a reference for sequential fuel injection to each cylinder.


 

Crankshaft Position (CKP) Sensor

The CKP sensor detects engine speed and is used by the PCM to determine ignition timing and timing for fuel injection of each cylinder.

 

Engine Coolant Temperature (ECT) Sensor

The ECT sensor is a temperature dependent resistor (thermistor). The resistor of the thermistor decreases as the engine coolant temperature increases.

 

i-DSI System

The PCM controls the ignition phase gap between the front and rear spark plugs in accordance with the engine speed and the vacuum in the intake manifold.

 

Ignition Timing Control

The PCM contains the memory for basic ignition timing at various engine speeds and manifold absolute pressure. It also adjusts the timing according to engine coolant temperature.

Injector Timing and Duration

The PCM contains the memory for basic discharge duration at various engine speeds and manifold pressures. The basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors to obtain the final discharge duration.
By monitoring long term fuel trim, the PCM detects long term malfunctions in the fuel system, and will set a Diagnostic Trouble Code (DTC).

Intake Air Temperature (IAT) Sensor

The IAT sensor is a temperature dependant resistor (thermistor). The resistance of the thermistor decreases as the intake air temperature increases.

 

Knock Sensor

The knock control system adjusts the ignition timing to minimize knock.

 


Manifold Absolute Pressure (MAP) Sensor

The MAP sensor converts manifold absolute pressure into electrical signals to the PCM.

 

Primary Heated Oxygen Sensor (Primary HO2S)

The primary HO2S detects the oxygen content in the exhaust gas and sends signals to the PCM which varies the duration of fuel injection accordingly. To stabilize its output, the sensor has an internal heater. The primary HO2S is installed in the exhaust manifold. By controlling the air fuel ratio with primary HO2S and secondary HO2S, the deterioration of the primary HO2S can be evaluated by its feedback period. When the feedback period exceeds a certain value during stable driving conditions, the sensor is considered deteriorated and the PCM sets a DTC.

 

Secondary Heated Oxygen Sensor (Secondary HO2S)

The secondary HO2S detects the oxygen content in the exhaust gas downstream of the Three Way Catalytic Converter (TWC) and sends signals to the PCM which varies the duration of fuel injection accordingly. To stabilize its output, the sensor has an internal heater. The secondary HO2S is installed in the TWC.

 

Starting Control

When the engine is started, the PCM provides a rich mixture by increasing injector duration.

Throttle Position (TP) Sensor

The TP sensor is a potentiometer connected to the throttle valve shaft. As the throttle position changes, the sensor varies the signal voltage to the PCM. The TP sensor is not available separately from the throttle body.

 

Idle Control System


When the engine is cold, the A/C compressor is on, the transmission is in gear, the brake pedal is pressed, the power steering load is high, or the alternator is charging, the PCM controls current to the Idle Air Control (IAC) valve to maintain the correct idle speed. Refer to the System Diagram to see the functional layout of the system.

Brake Pedal Position Switch

The brake pedal position switch signals the PCM when the brake pedal is pressed.

Idle Air Control (IAC) Valve

To maintain the proper idle speed, the IAC valve changes the amount of air bypassing the throttle body in response to an electrical signal from the PCM.

 

Fuel Supply System


Fuel Cut-off Control

During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at speeds over 800 rpm (min-1). Fuel cut-off action also occurs when engine speed exceeds 6,200 rpm (min-1), regardless of the position of the throttle valve, to protect the engine from over-revving. When the vehicle is stopped, the PCM cuts the fuel at engine speeds over 5,000 rpm (min-1). Fuel cut-off engine speed is lower on a cold engine.

Fuel Pump Control

When the ignition is turned on, the PCM grounds the PGM-FI main relay which feeds current to the fuel pump for 2 seconds to pressurize the fuel system. With the engine running, the PCM grounds the PGM-FI main relay and feeds current to the fuel pump. When the engine is not running and the ignition is on, the PCM cuts ground to the PGM-FI main relay which cuts current to the fuel pump.

PGM-FI Main Relay 1 and 2

The PGM-FI relay consists of two separate relays. The PGM-FI main relay 1 is energized whenever the ignition switch is ON (II) which supplies battery voltage to the PCM, power to the injectors, and power for the PGM-FI main relay 2. The PGM-FI main relay 2 is energized to supply power to the fuel pump for 2 seconds when the ignition switch is turned ON (II), and when the engine is running.

Intake Air System


Refer to the System Diagram to see the functional layout of the system.

Throttle Body

The throttle body is a single-barrel side draft type. The lower portion of the IAC valve is heated by engine coolant from the cylinder head.

 


Catalytic Converter System


Three Way Catalytic Converter (TWC)

The TWC converts hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to carbon dioxide (CO2), dinitrogen (N2), and water vapor.

 

Positive Crankcase Ventilation (PCV) System


The PCV valve prevents blow-by gasses from escaping into the atmosphere by venting them into the intake manifold.

 


Evaporative Emission (EVAP) Control System


Refer to the System Diagram to see the functional layout of the system.

EVAP Canister

The EVAP canister temporarily stores fuel vapor from the fuel tank until it can be purged back into the engine and burned (refer to the System Diagram to see the functional layout of the system).

EVAP Canister Purge Valve

When the engine coolant temperature is below 65°C (149°F), the PCM turns off the EVAP canister purge valve which cuts vacuum to the EVAP canister.

Idle Control System Diagram


The idle speed of the engine is controlled by the Idle Air Control (IAC) valve:

 

Intake Air System Diagram


This system supplies air for engine needs. A resonator in the intake air pipe provides additional silencing as air is drawn into the system.

 

Exhaust Gas Recirculation (EGR) System Diagram


The EGR system reduces oxides of nitrogen (NOx) emissions by recirculating exhaust gas through the EGR valve and the intake manifold into the combustion chambers. The PCM memory includes the ideal EGR valve position for varying operating conditions.

The EGR valve position sensor detects the amount of EGR valve lift and sends it to the PCM. The PCM then compares it with the ideal lift in its memory (based on signals sent from other sensors). If there is any difference between the two, the PCM cuts current to the EGR valve.

 

Evaporative Emission (EVAP) Control Diagram


The EVAP controls minimize the amount of fuel vapor escaping to the atmosphere. Vapor from the fuel tank is temporally stored in the EVAP canister until it can be purged from the EVAP canister into the engine and burned.