Fuel and Emissions System Description - L15A1(IN model) and L15A6

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 a 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 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 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 informs the driver by turning on the MIL.

ECM/PCM Data (L15A1 engine for IN model and L15A6 engine)


You can retrieve data from the ECM/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 ECM/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 ECM/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:
L15A1 engine for IN model and L15A6 engine
750±50 rpm (min-1
YES 
Vehicle Speed The ECM/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 ECM/PCM. The sensor is a thermistor whose internal resistance changes with coolant temperature. The ECM/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 ECM/PCM. Based on these signals, the ECM/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 

ECM/PCM Data (L15A1 engine for IN model and L15A6 engine) (cont'd)


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 ECM/PCM determines the air/fuel ratio and controls the amount of injected fuel.
Open: ignoring the A/F sensor and HO2S output, the ECM/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 ECM/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 ECM/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. 
0.72-1.35 YES 
Intake Air Temperature (IAT) The IAT sensor converts intake air temperature into voltage and signals the ECM/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 ECM/PCM. The ECM/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) without load:
15-25 % 
YES 

L15A1 engine for IN model and L15A6 engine


ECM/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 PHO2SHTC (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 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 
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 1.0 V at all times 
11 GRN/WHT SG1 (SENSOR GROUND) Sensor ground Less than 1.0 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: 1.2-2.0 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 

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

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
   18*1 BLU/WHT VSS (VEHICLE SPEED SENSOR (VSS)) Detects VSS signal With ignition switch ON (II) and front wheels rotating: cycles 0-about 5 V or battery voltage 
   18*2 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 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 
26 GRN CMP (CAMSHAFT POSITION (CMP) SENSOR) (TOP DEAD CENTER (TDC) SENSOR) Detects CMP (TDC) sensor With engine running: pulses 
27 WHT/BLU 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/BLK IGPLS3 (No. 3 IGNITION COIL PULSE) Drives No. 3 ignition coil 
29 WHT/GRN IGPLS2 (No. 2 IGNITION COIL PULSE) Drives No. 2 ignition coil 
30 WHT IGPLS1 (No. 1 IGNITION COIL PULSE) Drives No. 1 ignition coil 

*1: M/T 
*2: CVT 

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

 

NOTE: Standard battery voltage is 12 V.

Terminal number Wire color Terminal name Description Signal 
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 
   7*2 GRN/WHT DNLS+ (CVT DRIVEN PULLEY CONTROL VALVE +SIDE) Drives CVT driven pulley control valve With ignition switch ON (II): pulsing signal 
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) 
   11*3 RED/WHT MIND (M INDICATOR) Drives M indicator light With M indicator light turned ON: about 6 V
With M indicator light turned OFF: 0 V voltage 
   12*2 LT GRN SIND (S INDICATOR) Drives S indicator light With S indicator light turned ON: about 6 V
With S indicator light turned OFF: 0 V voltage 
13 WHT/RED ALTF (ALTERNATOR FR SIGNAL) Detects alternator FR signal With engine running: about 0-5 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 
15 GRN/YEL VTS (VTEC SOLENOID VALVE) Drivers VTEC solenoid valve At idle: about 0V 
   16*2 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 0.1-4.8 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) 
   19*3 LT GRN/RED S-DN (DOWNSHIFT SWITCH) Detects downshift switch signal Steering shift switch pushed toward downshift position (marked with -): 0 V
Steering shift switch in neutral position: about 5 V 
   20*3 YEL S-UP (UPSHIFT SWITCH) Detects upshift switch signal Steering shift switch pushed toward upshift position (marked with +): 0 V
Steering shift switch in neutral position: about 5 V 
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 
   24*2 BLU/WHT DRLS+ (CVT DRIVE PULLEY CONTROL VALVE +SIDE) Drives CVT drive pulley control valve With ignition switch ON (II): duty controlled 

*2: CVT 
*3: HONDA CVT+7SPEED MODE system 

PCM Inputs and Outputs at Connector C (22P)*2

 

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  
BLK 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 
   13*3 YEL MSW (MAIN SWITCH) Detects main switch
(7SPEED MODE) signal 
Main switch (7SPPED MODE) pushed: 0 V
Main switch (7SPPED MODE) released: about 5 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 

*2: CVT 
*3: HONDA CVT+7SPEED MODE system 

ECM/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 SHO2SHTC (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 
   8*3 BLU/WHT LED A Drives shift indicator In 7SPEED MODE:
  • in 1st, 2nd, 3rd and 7th: about 0.3 V
  • in 4th, 5th and 6th: about 5 V
 
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: about 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*2 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: about 0 V 
   15*4 GRN/RED ELD (ELECTRICAL LOAD DETECTOR (ELD)) Detects ELD signal With ignition switch ON (II): about 0.1-4.8 V (depending on electrical load) 

*2: CVT 
*3: HONDA CVT+7SPEED MODE system 
*4: L15A1 engine for IN model 

ECM/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 
   20*3 GRN/BLK LED C Drives shift indicator In 7SPEED MODE:
  • in 2nd, 4th, 6th and 7th: about 0.3 V
  • in 1st, 3rd and 5th: about 5 V
 
   21*3 RED/WHT LED B Drives shift indicator In 7SPEED MODE:
  • in 1st, 4th, 5th and 7th: about 0.3 V
  • in 2nd, 3rd and 6th: about 5 V
 
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 scan tool signal With ignition switch ON (II): battery voltage 
24 GRN MTRTW Sends engine coolant temperature 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 PGM Tester: 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 0V 
31 GRN/ORN MIL (MALFUNCTION INDICATOR LAMP) Drives MIL With MIL turned ON: about 0 V
With MIL turned OFF: battery voltage 

*3: HONDA CVT+7SPEED MODE system 

Vacuum Hose Routing


 

Vacuum Distribution


L15A1 engine for IN model and L15A6 engine 

PGM-FI System (L15A1 engine for IN model and L15A6 engine)


The programmed fuel injection (PGM-FI) system is a sequential multiport fuel injection system.

Air Conditioning (A/C) Compressor Clutch Relay

When the engine control module (ECM)/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 ECM/PCM during charging.

Barometric Pressure (BARO) Sensor

The BARO sensor is inside the ECM/PCM. It converts atmospheric pressure into a voltage signal that the ECM/ 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 determines 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.

 

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 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 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.

 

Vehicle Speed Sensor (VSS) (M/T model only)

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 System (L15A1 engine for IN model and L15A6 engine)







 

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.

 

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 900 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 6,200 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

The PGM-FI relay consists of two separate relays. 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.

 

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 (L15A1 engine for IN model and L15A6 engine)


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 70 °C (158 °F), the ECM/PCM turns off the EVAP canister purge valve which cuts vacuum to the EVAP canister.

Idle Control System Diagram (L15A1 engine for IN model and L15A6 engine)


The idle speed of the engine is controlled by the idle air control (IAC) valve:

 

Intake Air System Diagram (L15A1 engine for IN model and L15A6 engine)


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 (L15A1 engine for IN model and L15A6 engine)


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 ECM/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 ECM/PCM. The ECM/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 ECM/PCM cuts current to the EGR valve.




 

Evaporative Emission (EVAP) Control Diagram (L15A1 engine for IN model and L15A6 engine)


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.