Fuel and Emissions System Description (KH)

Electronic Control System


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

Self-diagnosis

The ECM/PCM detects a failure of a signal from a sensor or from another control unit and stores a Temporary DTC or a DTC. Depending on the failure a DTC is stored in the first or second drive cycle. When a DTC is stored, the ECM/PCM turns on the malfunction indicator lamp (MIL) by supplying ground to the MIL circuit.



Fail-safe Function

When an abnormality occurs in the signal from a sensor or from another control unit, the ECM/PCM ignores that signal and assumes a pre-programmed value that allows the engine to continue running. A DTC is stored, the MIL comes on.

MIL Bulb Check

When the ignition switch is first turned ON (II), the ECM/PCM supplies ground to the MIL circuit for 2 seconds to the check the bulb condition.

Self Shut Down (SSD) Mode

After the ignition switch is turned OFF, the ECM/PCM stays on (up to 15 minutes) to monitor the vehicle. If the ECM/PCM connector is disconnected during this time, 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 turning the ignition switch 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 
   1*3 BLK/WHT PO2SHTC (PRIMARY HEATED OXYGEN SENSOR 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 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 the ECM/PCM circuit With ignition switch ON (II): battery voltage
With ignition switch OFF: about 0 V 
BLK PG2 (POWER GROUND) Ground for the ECM/PCM circuit Less than 1.0 V at all times 
BLK PG1 (POWER GROUND) Ground for the ECM/PCM circuit Less than 1.0 V at all times 
RED PHO2S (PRIMARY HEATED OXYGEN SENSOR, 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 ignition ON (II): about 0 V
With engine knocking: pulses 
10 GRN/YEL SG2 (SENSOR GROUND) Sensor ground Less than 1.0 V at all times 
11 GRN/WHT SG1 (SENSOR GROUND) Sensor ground Less than 1.0 V at all times 
12 BLK/RED IACV (IDLE AIR CONTROL (IAC) VALVE) Drives IAC valve With engine running: duty controlled 
15 RED/BLK TPS (THROTTLE POSITION SENSOR) Detects TP sensor signal With throttle fully open: about 4.8 V
With throttle fully closed: about 0.5 V 
   18*2 WHT/GRN VSS (VEHICLE SPEED SENSOR) Detects VSS signal With ignition switch ON (II) and front wheels rotating: cycles about 0 V-about 5 V or battery voltage 
19 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) 
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 ECM/PCM circuit Less than 1.0 V at all times 
24 BRN/YEL LG1 (LOGIC GROUND) Ground for the ECM/PCM circuit Less than 1.0 V at all times 
25 BLU/WHT CMP (CAMSHAFT POSITION SENSOR) Detects CMP sensor signal With engine running: pulses 
26 GRN TDC (TOP DEAD CENTER SENSOR) Detects TDC sensor With engine running: pulses 
27 BRN IGPLS4 (No. 4 IGNITION COIL PULSE) Drives No. 4 ignition coil With ignition switch ON (II): about 0 V
With engine running: pulses 
28 WHT/BLU IGPLS3 (No. 3 IGNITION COIL PULSE) Drives No. 3 ignition coil 
29 BLU/RED IGPLS2 (No. 2 IGNITION COIL PULSE) Drives No. 2 ignition coil 
30 YEL/GRN IGPLS1 (No. 1 IGNITION COIL PULSE) Drives No. 1 ignition coil 

*2: M/T 

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 +SIDE) 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 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 FANC (RADIATOR FAN CONTROL) Drives radiator fan relay With radiator fan running: about 0 V
With radiator fan stopped: battery voltage 
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) 
BLU/BLK VTPSW (VTEC OIL PRESSURE SWITCH) Detects VTEC oil pressure switch signal At idle: about 0 V 
10 WHT/BLU ALTL (ALTERNATOR L SIGNAL) Detects alternator L signal With ignition switch ON (II): about 0 V
With engine running: battery voltage 
13 WHT/RED ALTF (ALTERNATOR FR SIGNAL) Detects alternator FR signal With engine running: about 0-5 V
(depending on electrical load) 
   14*1 RED/BLK LSA+ (A/T PRESSURE CONTROL SOLENOID VALVE A +SIDE) Drives A/T pressure control solenoid valve A With ignition switch ON (II): duty controlled 
15 GRN/YEL VTS (VTEC SOLENOID VALVE) Drives VTEC solenoid valve At idle: about 0 V 
   16*1 BRN/WHT LSB+ (A/T PRESSURE CONTROL SOLENOID VALVE B +SIDE) Drives A/T pressure control solenoid valve B With ignition switch ON (II): duty controlled 
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: about 0-5 V
(depending on electrical load) 
21 YEL/BLU PCS (EVAPORATIVE EMISSION 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 RED/BLU IMT (INTAKE MANIFOLD TUNING CONTROL SOLENOID VALVE) (IMRC (INTAKE MANIFOLD RUNNER CONTROL SOLENOID VALVE)) Drives IMT (IMRC) solenoid valve With engine speed below 4,700 rpm (min-1): battery voltage
With engine speed above 4,700 rpm (min-1): 0 V 
23 BLK/WHT VTC- (VTC OIL CONTROL SOLENOID VALVE -SIDE) Drives VTC oil control solenoid valve With ignition switch ON (II): 0 V 
   24*1 BLU/YEL LSC+ (A/T PRESSURE CONTROL SOLENOID VALVE C +SIDE) Drives A/T pressure control solenoid valve C With ignition switch ON (II): duty controlled 

*1: A/T 

PCM Inputs and Outputs at Connector C (22P)*1

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
WHT/BLK LSA- (A/T PRESSURE CONTROL SOLENOID VALVE A -SIDE) Ground for A/T pressure control solenoid valve A  
GRN SHC (SHIFT SOLENOID VALVE C) Drives shift solenoid valve C With engine running in neutral position, or in D position (in 1st, 3rd gears): battery voltage
With engine running in Park, R position, or in D position (in 2nd, 4th gears): about 0 V 
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 position (in 1st, 2nd, 3rd, 4th gears): about 0 V 
GRN/WHT SHB (SHIFT SOLENOID VALVE B) Drives shift solenoid valve B With engine running in Park, R, neutral position, or D position (in 1st, 2nd gears): battery voltage
With engine running in D position (in 3rd, 4th gears): about 0 V 
BLU/BLK SHA (SHIFT SOLENOID VALVE A) Drives shift solenoid valve A With engine running in R position, or D position (in 1st, 4th gears): battery voltage
With engine running in Park, neutral position, or D position (in 2nd, 3rd gears): about 0 V 
WHT/RED NM (MAINSHAFT SPEED SENSOR) Detects mainshaft speed sensor signals With engine running: pulses 
BLK/RED LSB- (A/T PRESSURE CONTROL SOLENOID VALVE B -SIDE) Ground for A/T pressure control solenoid valve B  
10 BLU/WHT OP3SW (3RD OIL PRESSURE SWITCH) Detects 3rd oil pressure switch With ignition switch ON (II): about 5 V
With engine running in 3rd gear: about 0 V 
11 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 RED/WHT ATPRVS (TRANSMISSION RANGE SWITCH R POSITION) Detects transmission range switch R position signal In R position: about 0 V
In any other position: about 5 V or battery voltage 
13 BLU/RED OP2SW (2ND OIL PRESSURE SWITCH) Detects 2nd oil pressure switch With ignition switch ON (II): about 5 V
With engine running in 2nd gear: about 0 V 
14 RED/YEL ATFT (ATF TEMPERATURE SENSOR) Detects ATF temperature sensor signal With ignition switch ON (II): about 0.1-4.2 V
(depending on ATF temperature) 
15 BLU NC (COUNTERSHAFT SPEED SENSOR) Detects countershaft speed sensor signals With ignition switch ON (II), and front wheels rotating: pulses 
16 WHT/BLU LSC- (A/T PRESSURE CONTROL SOLENOID VALVE C -SIDE) Ground for A/T pressure control solenoid valve C With ignition switch ON (II): duty controlled 
19 BRN ATP1 (TRANSMISSION RANGE SWITCH 1ST POSITION) Detects transmission range switch 1st position signal In 1st position: about 0 V
In any other position: battery voltage 

*1: A/T 

PCM Inputs and Outputs at Connector D (17P)*1

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
GRN D3SW (D3 SWITCH) Detects D3 switch signal With D3 switch OFF: about 5 V
With D3 switch ON: about 0 V 
BLK/RED ATPN (TRANSMISSION RANGE SWITCH NEUTRAL POSITION) Detects transmission range switch neutral position signal In neutral position: about 0 V
In any other position: about 5 V or battery voltage 
WHT ATPR (TRANSMISSION RANGE SWITCH R POSITION) Detects transmission range switch R position signal In R position: about 0 V
In any other position: about 5 V or battery voltage 
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: about 5 V or battery voltage 
10 WHT/GRN 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 or battery voltage 

*1: A/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 
GRN/YEL IMOFPR (IMMOBILIZER FUEL PUMP RELAY) Drives PGM-FI main ralay 2 0 V for 2 seconds after turning ignition switch ON (II), then battery voltage 
WHT/RED SHO2S (SECONDARY HEATED OXYGEN SENSOR, 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 ECM/PCM control circuit Less than 1.0 V at all times 
WHT/BLK SG3 (SENSOR GROUND) Sensor ground Less than 1.0 V at all times 
BLK/WHT SO2SHTC (SECONDARY HEATED OXYGEN SENSOR 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): battery voltage
With ignition switch OFF: about 0 V 
YEL/BLK IG1 (IGNITION SIGNAL) Detects ignition signal With ignition switch ON (II): battery voltage
With ignition switch OFF: about 0 V 
13 WHT/BLU SLC (SHIFT LOCK SOLENOID) Drives shift lock solenoid With ignition switch ON (II) in Park position and brake pedal pressed and accelerator released: 8.5 V 
15 GRN/RED ELD (ELECTRICAL LOAD DETECTOR) Drives 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 steering wheel in straight ahead position: about 0 V
At idle with steering wheel at full lock: 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 
22 WHT/BLK BKSW (BRAKE PEDAL POSITION SWITCH) Detects BPP switch signal With brake pedal released: about 0 V
With brake pedal pressed: battery voltage 
23 LT BLU K-LINE Sends and receives HDS or scan tool signal With ignition switch ON (II): pulses or battery voltage 
24 YEL SEFMJ Communicates with multiplex control unit With ignition switch ON (II): about 5 V
With engine running with load: pulses 
   25*1 BLU/WHT VSSOUT (VEHICLE SPEED SENSOR 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 
27 WHT IMOCD (IMMOBILIZER CODE) Detects immobilizer signal  
29 BRN SCS (SERVICE CHECK SIGNAL) Detects service check signal With the service check signal shorted with the HDS or a scan tool: about 0 V
With the service check signal opened: about 5 V battery voltage 
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 

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.

Alternator Control

The alternator signals the engine control module (ECM)/ powertrain control module (PCM) during charging.

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.

Crankshaft Position (CKP) Sensor

The CKP sensor detects crankshaft speed and determines 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 resistor 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.

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 will set 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.

 

Primary Heated Oxygen Sensor (Primary HO2S)

The primary HO2S detects the oxygen content in the exhaust gas 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 primary HO2S is installed in the three way catalytic converter (TWC). 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 ECM/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 ECM/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 ECM/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 ECM/PCM. The TP sensor is not replaceable apart from the throttle body.

 

Top Dead Center (TDC) Sensor

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

 

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.

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 emission. 
(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

 

System Diagram

 

Camshaft Position (CMP) Sensor

The CMP 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 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 ECM/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 ECM/PCM.

 

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 speeds over 850 rpm (min-1). Fuel cut-off action also occurs when engine speed exceeds 6,900 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) (A/T: 5,000 rpm (min-1)).

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

PGM-FI main relay 1 is energized whenever the ignition switch is ON (II) which supplies 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 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.

 

Intake Air Bypass Control Thermal Valve

When the engine is running, the intake air bypass control thermal valve sends 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.

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.

 

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.


 

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.