Fuel and Emissions System Description

Electronic Control System


The functions of the fuel and emission control systems are managed by the engine control module (ECM) on vehicles with manual transmissions or the powertrain control module (PCM) on vehicles with automatic transmissions.

Fail-safe Function

When an abnormality occurs in the signal from a sensor, the ECM/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 ECM/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 ECM/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 ECM/PCM supplies ground to the MIL for 2 seconds to check the MIL bulb condition. The MIL may be turned off by the ECM/PCM if the problem that originally caused the MIL to be illuminated is a intermittent one.

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 ECM/PCM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON (II) again, the ECM/PCM turns on the MIL.

Self Shut Down Mode (SSD)

After the ignition switch is turned off, the ECM/PCM stays ON (up to 15 minutes).
If the ECM/PCM connector is disconnected during this mode, the ECM/PCM may be damaged.
To cancel this mode, disconnect the negative cable from the battery or jump the SCS line with the HDS after the ignition switch is turned off.

ECM/PCM Inputs and Outputs at Connector A (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
RED/BLU KS (KNOCK SENSOR) Detects knock sensor signal With engine knocking: pulses 
YEL/BLK IGP2 (POWER SOURCE) Power source for ECM/PCM circuit With ignition switch ON (II): battery voltage
With ignition switch OFF: about 0 V 
YEL/BLK IGP1 (POWER SOURCE) Power source for ECM/PCM circuit With ignition switch ON (II): battery voltage
With ignition switch OFF: about 0 V 
BLK PG2 (POWER GROUND) Ground circuit for the ECM/PCM Less than 1.0 V at all times 
BLK PG1 (POWER GROUND) Ground circuit for the ECM/PCM Less than 1.0 V at all times 
GRN CMPB (CAMSHAFT POSITION SENSOR B) Detects CMP sensor B signal With engine running: pulses
With the ignition switch ON (II): about 5 V 
BLU CKP (CRANKSHAFT POSITION SENSOR) Detects CKP sensor signal With engine running: pulses
With the ignition switch ON (II): about 5 V 
BRN/YEL LG2 (LOGIC GROUND) Ground circuit for ECM/PCM Less than 1.0 V at all times 
BRN/YEL LG1 (LOGIC GROUND) Ground circuit for ECM/PCM Less than 1.0 V at all times 
10 BLK/WHT AFSHTC (AIR FUEL RATIO (A/F) SENSOR HEATER CONTROL) Drives A/F sensor heater With ignition switch ON (II): battery voltage
With fully warmed up engine running: about 0 V 
11 RED/BLU IMT (INTAKE MANIFOLD TUNING SOLENOID VALVE) (IMRC (INTAKE MANIFOLD RUNNER CONTROL SOLENOID VALVE)) Drives IMT (IMRC) solenoid valve With engine speed below 4,300 rpm (min-1): battery voltage
With engine speed above 4,300 rpm (min-1): 0 V 
13 BRN IGPLS4 (No. 4 IGNITION COIL PULSE) Drives No. 4 ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
14 WHT/BLU IGPLS3 (No. 3 IGNITION COIL PULSE) Drives No. 3 ignition coil 
15 BLU/RED IGPLS2 (No. 2 IGNITION COIL PULSE) Drives No. 2 ignition coil 
16 YEL/GRN IGPLS1 (No. 1 IGNITION COIL PULSE) Drives No. 1 ignition coil 
   18*1 BLU NC (COUNTERSHAFT SPEED SENSOR) Detects countershaft speed sensor signal With ignition switch ON (II): about 0 V or about 5 V
While driving: about 2.5 V 
   18*2 WHT/GRN VSS (VEHICLE SPEED SENSOR) Detects VSS signal With ignition switch ON (II) and front wheels rotating:
cycles about 0-about 5 V or battery voltage 
19 BLU/WHT CMP A (CAMSHAFT POSITION SENSOR A) Detects CMP sensor A signal With engine running: pulses
With ignition switch ON (II): about 5 V 

*1: A/T 
*2: M/T 

ECM/PCM Inputs and Outputs at Connector A (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
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 GRN/YEL SG2 (SENSOR GROUND) Sensor ground Less than 1.0 V at all times 
24 GRN/WHT SG1 (SENSOR GROUND) Sensor ground Less than 1.0 V at all times 
25 RED/YEL APSB (ACCELERATOR PEDAL POSITION (APP) SENSOR B) Detects APP sensor B signal With ignition switch ON (II) and accelerator pedal pressed: about 2.3 V
With ignition switch ON (II) and accelerator pedal released: about 0.2 V 
26 RED/BLU APSA (ACCELERATOR PEDAL POSITION (APP) SENSOR A) Detects APP sensor A signal With ignition switch ON (II) and accelerator pedal pressed: about 4.5 V
With ignition switch ON (II) and accelerator pedal released: about 0.5 V 
28 RED/YEL AFS- (AIR FUEL RATIO (A/F) SENSOR, SENSOR 1 -SIDE) Detects A/F sensor (Sensor 1) signal  
30 GRN/RED MAP (MANIFOLD ABSOLUTE PRESSURE SENSOR) Detects MAP sensor signal With ignition switch ON (II): about 3 V
At idle: about 1.0 V (depending on engine speed) 
31 RED AFS+ (AIR FUEL RATIO (A/F) SENSOR, SENSOR 1 +SIDE) Detects A/F sensor (Sensor 1) signal  

ECM/PCM Inputs and Outputs at Connector B (24P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
BLU/WHT VTC (VTC OIL CONTROL SOLENOID VALVE) Drives VTC oil control solenoid valve With ignition switch ON (II): 0 V 
YEL INJ4 (No. 4 INJECTOR) Drives No. 4 injector At idle: duty controlled
With the ignition switch ON (II): battery voltage 
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/YEL VTS (VTEC SOLENOID VALVE) Drives VTEC solenoid valve At idle: about 0 V 
RED/WHT ECT (ENGINE COOLANT TEMPERATURE SENSOR) Detects ECT sensor signal With ignition switch ON (II): about 0.1-4.8 V
(depending on engine coolant temperature)
With fully warmed up engine: about 0.5-0.7 V 
10 WHT/BLU ALTL (ALTERNATOR L SIGNAL) Detects alternator signal With ignition switch ON (II): about 0 V
With engine running: battery voltage 
   11*5 BLU/BLK VTPSW (VTEC OIL PRESSURE SWITCH) Detects VTEC oil pressure switch signal With engine at low engine speed: about 0 V
With engine at high engine speed: battery voltage 
13 WHT/RED ALTF (ALTERNATOR FR SIGNAL) Detects alternator FR signal With engine running: about 0-5 V
(depending on electrical load) 
17 RED/YEL IAT (INTAKE AIR TEMPERATURE SENSOR) Detects IAT sensor signal With ignition switch ON (II): about 0.1-4.8 V
(depending on intake air temperature) 
18 WHT/GRN ALTC (ALTERNATOR CONTROL) Sends alternator control signal With engine running:
and fully warmed up: about 8 V 
   19*3 GRN SEFD (SERIAL SIGNAL) Sends VSA control serial signal  
   20*3 BLU SEDF (SERIAL SIGNAL) Detects VSA control serial signal  
21 YEL/BLU PCS (EVAPORATIVE EMISSION CANISTER PURGE VALVE) Drives EVAP canister purge valve With engine running, engine coolant below 65 °C (149 °F): battery voltage
With engine running, engine coolant above 65 °C (149 °F): duty controlled 

*3: with VSA 
*5: KE, KG, KM, KQ, KS models 

PCM Inputs and Outputs at Connector C (22P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
  1*1 RED/BLK LSA (A/T CLUTCH PRESSURE CONTROL SOLENOID VALVE A) Drives A/T clutch pressure control solenoid valve A With ignition switch ON (II): duty controlled 
   2*1 GRN SHC (SHIFT SOLENOID VALVE C) Drives shift solenoid valve C With engine running in Neutral and 1 position, or in D position (in 1st, 3rd gears): battery voltage
With engine running in Park, R position, 2, D or D3 position (in 2nd, 4th gears): about 0 V 
   3*1 YEL SHE (SHIFT SOLENOID VALVE E) Drives shift solenoid valve E With engine running in Park, R position: battery voltage
With engine running in Neutral position, or in D, 2, and 1 position: about 0 V 
   4*1 GRN/WHT SHB (SHIFT SOLENOID VALVE B) Drives shift solenoid valve B With engine running in Park, R, Neutral, 2, and 1 position, or D position (in 1st, 2nd gears): battery voltage
With engine running in D position (in 3rd, 4th, 5th gears): about 0 V 
   5*4 GRN/RED SHD (SHIFT SOLENOID VALVE D) Drives shift solenoid valve D With engine running in 2 or D position (in 2nd gears): battery voltage
With engine running in Park, R, Neutral, 1 position, or D position (in 1st, 3rd, 4th, gears): about 0 V 
   6*1 BLU/BLK SHA (SHIFT SOLENOID VALVE A) Drives shift solenoid valve A With engine running in R and 1 position, or D position (in 1st, 4th gears): battery voltage
With engine running in Park, Neutral and 2 position, or D, D3 position (in 2nd, 3rd gears): about 0 V 
   7*1 BLU/YEL LSC (A/T CLUTCH PRESSURE CONTROL SOLENOID VALVE C) Drivers A/T clutch pressure control solenoid valve C With the ignition switch ON (II): duty controlled 
   9*1 BRN ATP1 (TRANSMISSION RANGE SWITCH 1 POSITION) Detects transmission range switch 1 position signal input In 1 position: about 0 V
In any other position: battery voltage 
  10*1 BLU/WHT OP3SW (3RD CLUTCH TRANSMISSION FLUID PRESSURE SWITCH) Detects 3rd oil clutch transmission fluid pressure switch signal output With ignition switch ON (II): about 5 V
With 3rd clutch pressure: 0 V 
  11*1 GRN/RED ATP2 (TRANSMISSION RANGE SWITCH 2ND POSITION) Detects transmission range switch 2nd position signal In 2nd position: about 0 V
In any other position: battery voltage 
  12*1 RED/WHT ATPRVS (TRANSMISSION RANGE SWITCH R POSITION) Detects transmission range switch R position signal input In R position: about 0 V
In any other position: battery voltage 
  13*1 BLU/RED OP2SW (2ND CLUTCH TRANSMISSION FLUID PRESSURE SWITCH) Detects 2nd clutch transmission fluid pressure switch signal input With ignition switch ON (II): about 5 V
With 2nd clutch pressure: 0 V 
  14*1 RED/YEL ATFT (ATF TEMPERATURE SENSOR) Detects ATF temperature sensor signal input With ignition switch ON (II): about 0.2-4.8 V
(depending on ATF temperature) 

*1: A/T 
*4: except KE, KG, KH, KS models (A/T) 

PCM Inputs and Outputs at Connector C (22P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
  15*1 BRN/WHT LSB (A/T CLUTCH PRESSURE CONTROL SOLENOID VALVE B) Drives A/T clutch pressure control solenoid valve B With the ignition switch ON (II): duty controlled 
  17*1 YEL ATPD (TRANSMISSION RANGE SWITCH D POSITION) Detects transmission range switch D position signal In D position: about 0 V
In any other position: battery voltage 
  18*1 YEL/RED ATPFWD (TRANSMISSION RANGE SWITCH D/D3 POSITION) Detects transmission range switch D, D3, 2 position signal In D, D3, and 2 position: about 0 V
In any other position: battery voltage 
  19*1 WHT/RED NM (MAINSHAFT SPEED SENSOR) Detects mainshaft speed sensor signal With ignition switch ON (II): about 0 V or about 5 V
With engine running in N position: about 2.5 V 
  20*1 RED/BLK ATPN (TRANSMISSION RANGE SWITCH NEUTRAL POSITION) Detects transmission range switch Neutral position signal In Neutral position: about 0 V
In any other position: battery voltage 

*1: A/T 

ECM/PCM Inputs and Outputs at Connector D (17P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
GRY/RED CRSETSW (CRUISE SET SWITCH) Detects cruise SET switch signal With cruise SET switch ON: 0 V
With cruise SET switch OFF: battey voltage 
   3*1 GRN D3SW (D3 SWITCH) Detects D3 switch signal With D3 switch OFF: about 5 V
With D3 switch ON: about 0 V 
LT GRN CRMSW (CRUISE MAIN SWITCH) Detects cruise MAIN switch signal With cruise MAIN switch ON: 0 V
With cruise MAIN switch OFF: battery voltage 
   5*1 WHT ATPR (TRANCMISSION RANGE SWITCH R POSITION) Detects transmission range switch R position signal In R position: about 0 V
In any other position: battery voltage 
   6*1 BLU/BLK ATPP (TRANSMISSION RANGE SWITCH PARK POSITION) Detects transmission range switch Park position signal In Park position: about 0 V
In any other position: battery voltage 
LT GRN/RED CRRESSW (CRUISE RES SWITCH) Detects cruise RES switch signal With cruise RES switch ON: 0 V
With cruise RES switch OFF: battery voltage 
BLU BKSWNC (BRAKE PEDAL POSITION SWITCH) Detects brake pedal position switch signal With ignition switch ON (II) and brake pedal released: battery voltage
With ignition switch ON (II) and brake pedal pressed: about 0 V 
   9*2 LT BLU CRMTCLS (CRUISE CLUTCH PEDAL POSITION SIGNAL) Detects cruise clutch pedal position switch signal With ignition switch ON (II) and clutch pedal released: about 0 V
With ignition switch ON (II) and clutch pedal pressed: battery voltage 
15 BRN/YEL DBWRLY (THROTTLE ACTUATOR CONTROL MODULE RELAY) Drives throttle actuator control module relay With ignition switch ON (II) and: 0 V 
16 BLU/YEL SETIND (CRUISE SET INDICATOR) Drives CRUISE CONTROL indicator With CRUISE CONTROL indicator turned ON:
about 0 V
With CRUISE CONTROL indicator turned OFF:
battery voltage 

*1: A/T 
*2: M/T 

ECM/PCM Inputs and Outputs at Connector E (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
  2*1 WHT/BLU SLC (SHIFT LOCK SOLENOID) Drives shift lock solenoid With ignition switch ON (II), in the Park position, brake pedal pressed, and accelerator released: 0 V 
BRN/YEL LG3 (LOGIC GROUND) Ground for ECM/PCM control circuit Less than 1.0 V at all times 
WHT/GRN SG3 (SENSOR GROUND) Sensor ground Less than 1.0 V at all times 
RED/YEL MRLY (PGM-FI MAIN RELAY) Drives PGM-FI main relay 1
Power source for DTC memory 
With ignition switch ON (II): about 0 V
With ignition switch OFF: battery voltage 
ORN AFSHTCR (AIR FUEL RATIO (A/F) SENSOR HEATER CONTROL RELAY) Drives A/F sensor heater relay With ignition switch ON (II): 0 V 
YEL/BLK IG1 (IGNITION SIGNAL) Detects ignition signal With ignition switch ON (II): battery voltage
With ignition switch OFF: about 0 V 
   11*3 WHT CAN H (CAN COMMUNICATION SIGNAL HIGH) Sends communication signal With ignition switch ON (II): pulses 
12 GRN/WHT FANC (RADIATOR FAN CONTROL) Drives radiator fan relay With radiator fan running: about 0 V
With radiator fan stopped: battery voltage 
13 YEL SEFMJ Communicates with multiplex control unit With ignition switch ON (II): about 5 V
With engine running with load: pulses 
15 GRN/RED ELD (ELECTRICAL LOAD DETECTOR) Detects ELD signal With ignition switch ON (II): about 0.1-4.8 V (depending on electrical load) 
16 LT GRN/BLK PSPSW (POWER STEERING PRESSURE SWITCH SIGNAL) Detects PSP switch signal At idle with steering wheel straight ahead: 0 V
At idle with steering wheel at full lock: battery voltage 
17 GRN/YEL IMO FPR (IMMOBILIZER FUEL PUMP RELAY) Drives PGM-FI main relay 2 (FUEL PUMP) 0 V for 2 seconds after turning ignition switch ON (II), then battery voltage 
18 RED ACC (A/C CLUTCH RELAY) Drives A/C clutch relay With compressor ON: about 0 V
With compressor OFF: battery voltage 
20 RED/BLU SHO2S (SECONDARY HEATED OXYGEN SENSOR (SECONDAY HO2S), SENSOR 2) Detects secondary HO2S (Sensor 2) signal With throttle fully closed and idle with fully warmed up engine: above 0.6 V
With throttle quickly closed: below 0.4 V 
21 BLK/WHT SHO2SHTC (SECONDARY HEATED OXYGEN SENSOR (SECONDAY HO2S) HEATER CONTROL) Drives secondary HO2S heater With ignition switch ON (II): battery voltage
With fully warmed up engine running: duty controlled 

*1: A/T 
*3: with VSA 

ECM/PCM Inputs and Outputs at Connector E (31P)

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
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 LT BLU K-LINE Sends and receives HDS signals With ignition switch ON (II): pulses or battery voltage 
   24*3 PNK CANL (CAN COMMUNICATION SIGNAL LOW) Sends the communication signal With ignition switch ON (II): pulses 
25 BLU NEP (ENGINE SPEED PULSE) Outputs engine speed pulse With engine running: pulses 
   26*1 BLU/WHT VSSOUT (VEHICLE SPEED SENSOR OUTPUT SIGNAL) Sends vehicle speed sensor signal Depending on vehicle speed: pulses
With ignition switch ON (II): battery voltage 
27 WHT IMOCD (IMMOBILIZER CODE) Detects immobilizer signal  
29 BRN SCS (SERVICE CHECK SIGNAL) Detects service check signal With the service check signal shorted using HDS: about 0 V
With the service check signal open: about 5 V 
30 RED/WHT WEN (WRITE ENABLE SIGNAL) Detects write enable signal With ignition switch ON (II): about 0 V 
31 GRN/WHT MIL (MALFUNCTION INDICATOR LAMP) Drives MIL With MIL turned ON: about 0 V
With MIL turned OFF: battery voltage 

*1: A/T 
*3: with VSA 

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 ECM/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.

Air Fuel Ratio (A/F) Sensor

The A/F sensor operates over a wide air/fuel range. The A/F sensor is installed upstream of the TWC, and sends signals to the ECM/PCM which varies the duration of fuel injection accordingly.

 

Barometric Pressure (BARO) Sensor

The BARO sensor is inside the ECM/PCM. It converts atmospheric pressure into a voltage signal that modifies the basic duration of the fuel injection discharge.

Camshaft Position (CMP) Sensor B

CMP sensor B 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 crankshaft speed and is used by the ECM/PCM to determine ignition timing and timing for fuel injection of each cylinder as well as detecting engine misfire.

 

Engine Coolant Temperature (ECT) Sensor

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

 

Ignition Timing Control

The ECM/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 and intake air temperature.

Injector Timing and Duration

The ECM/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 ECM/PCM detects long term malfunctions in the fuel system and sets a diagnostic trouble code (DTC).

Intake Air Temperature (IAT) Sensor

The IAT sensor is a temperature dependent 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 ECM/PCM.

 

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 ECM/PCM which varies the duration of fuel injection accordingly. To stabilize its output, the sensor has an internal heater. The ECM/PCM compares the HO2S output with the A/F sensor output to determine catalyst efficiency. The secondary HO2S is located on the TWC.

 

Vehicle Speed Sensor (VSS) (M/T)

The VSS is driven by the differential. It generates a pulsed signal from an input of 5 volts. The number of pulses per minute increases/decreases with the speed of the vehicle.

 

Electronic Throttle Control System


The throttle is electronically controlled by the electronic throttle control system. Refer to the System Diagram to see the functional layout of the system.

Idle control: When the engine is idling, the ECM/PCM controls the throttle actuator to maintain the proper idle speed according to engine loads.

Acceleration control: When the accelerator pedal is pressed, the ECM/PCM opens the throttle valve depending on the accelerator pedal position (APP) sensor signal.
Cruise control: The ECM/PCM controls the throttle actuator to maintain set speed when the cruise control is operating. The throttle actuator takes the place of the cruise control actuator.

Accelerator Pedal Position (APP) Sensor

As the accelerator pedal position changes, the sensor varies the signal voltage to the ECM/PCM.

 

 

Throttle Body

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

 

VTEC/VTC


 

Driving Condition VTC Control Description 
(1) Light-load Base Position For stable combustion the cam angle is retarded, and reduces the entry of exhaust gas into the cylinder.  
(2) Medium/high-load Advance Control Cam phase angle is controlled to optimize valve timing, improving fuel efficiency and reducing emissions. 
(3) High speed Advance-Base Position To reduce the pumping loss, the intake valve is closed quickly. This helps the entry of fuel air mixture by the charging effect, and maximizes engine power. 

VTC system

 

VTEC system

 

VTEC/VTC


System Diagram 

Camshaft Position (CMP) Sensor A

This sensor detects camshaft angle position for the VTC system.

 

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 ECM/PCM controls current to the throttle actuator to maintain the correct idle speed.

Brake Pedal Position Switch

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

Power Steering Pressure (PSP) Switch

The PSP switch signals the ECM/PCM when the power steering load is high.

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 engine speeds over 1,000 rpm (min-1). Fuel cut-off control also occurs when the engine speed exceeds 6,900 rpm (min-1) (K24A1 engine: 6,700 rpm (min-1)), regardless of the position of the throttle valve, to protect the engine from over-revving. When the vehicle is stopped, the ECM/PCM cuts the fuel at engine speeds over 6,500 rpm (min-1) (K24A1 engine M/T: 5,000rpm (min-1), A/T: 6,700 (min-1)). Engine speed of fuel cut is lower on a cold engine.

Fuel Pump Control

When the ignition is turned on, the ECM/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 ECM/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 ECM/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. PGM-FI main relay 1 is energized whenever the ignition switch is ON (II) to supply battery voltage to the ECM/PCM, power to the injectors, and power for PGM-FI main relay 2. 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 cranking or running.

Intake Air System


This system supplies air for engine needs.

Intake Air Bypass Control Thermal Valve

When the engine is cold, the intake air bypass control thermal valve sends air to the injector.
The amount of air is regulated by engine coolant temperature. Once the engine is hot, the intake air bypass control thermal valve closes, stopping air to the injector.

 

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 ECM/PCM turns off the EVAP canister purge valve which cuts vacuum to the EVAP canister.

Intake Manifold Tuning (IMT) (Intake Manifold Runner Control (IMRC)) System


Satisfactory power performance is achieved by closing and opening the intake manifold tuning (IMT) (intake manifold runner control (IMRC)) valve. High torque at low engine speed is achieved when the valve is closed, whereas high power at high engine is achieved when the valve is opened.




 

Electronic Throttle Control System Diagram


The electronic throttle control system consists of the throttle actuator, throttle position (TP) sensor, accelerator pedal position (APP) sensor, throttle actuator control module, and the ECM/PCM. The throttle is electronically controlled by this system.



 

Evaporative Emission (EVAP) Control Diagram


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