Contents Section: Testing & Diagnostics All sections

Fuel System & Emissions System (K20Z3 Engine): Other Honda Civic VIII рестайлинг

Testing & Diagnostics 48 illustrations ~4518 words

Intermittent Failures

The term intermittent failure means a system may have had a failure, but it checks OK now. If the malfunction indicator lamp (MIL) on the dash does not come on, check for poor connections or loose terminals at all connectors related to the circuit that you are troubleshooting. If the MIL was on but then went out, the original problem may have been intermittent.

Service Information

Periodically, new ECM software or new service procedures may become available. Always check online for the latest software or service information related to the DTCs or symptoms you are troubleshooting.

Opens and Shorts

Open and short are common electrical terms. An open is a break in a wire or at a connection. A short is an accidental connection of a wire to ground or to another wire. In simple electronics, this usually means something won't work at all. With complex electronics (such as ECMs) this can sometimes mean something works, but not the way it's supposed to.

Scheme 954

Scheme 954: If the MIL (malfunction indicator lamp) has come on

Scheme 955

Scheme 955
  1. Start the engine, and check the MIL (A). NOTE: If the ignition switch is turned to ON (II), and the engine is not started, the MIL stays on for 15-20 seconds (see «HOW TO SET READINESS CODES»(ref-379880-S34005236942010121600000) ).
  2. If the MIL stays on, connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
  3. Turn the ignition switch to ON (II).
  4. Make sure the HDS communicates with the ECM and other vehicle systems. If it doesn't, go to the DLC circuit troubleshooting (see «DLC CIRCUIT TROUBLESHOOTING»(ref-355119-S04276123312010012000000) ).
  5. Check the diagnostic trouble code (DTC) and note it. Also check the freeze data and/or on-board snapshot data, and download any data found. Then refer to the indicated DTC's troubleshooting, and begin the appropriate troubleshooting procedure. NOTE: Freeze data indicates the engine conditions when the first malfunction, misfire, or fuel trim malfunction that activated the MIL was detected. The HDS can read the DTC, the freeze data, the on-board snapshot, the current data, and other engine control module (ECM) data. For specific operations, refer to the user's manual that came with the HDS.
  6. If no DTCs are found, go to the MIL circuit troubleshooting (see «MIL CIRCUIT TROUBLESHOOTING»(ref-355119-S12907777652010012000000) ).

If the MIL did not stay on

If the MIL did not stay on but there is a driveability problem, do the symptom troubleshooting.

HDS Clear Command

The ECM stores various specific data to correct the system even if there is no electrical power, such as when the battery negative terminal or the No. 19 Fl MAIN (15 A) fuse is disconnected. Stored data based on failed parts should be cleared by using the CLEAR COMMAND of the HDS, if parts are replaced.

The HDS has three kinds of clear commands to meet this purpose. They are DTC clear, ECM reset, and CKP pattern clear. The DTC clear command erases all stored DTC codes, freeze data, on-board snapshot, and readiness codes. This must be done with the HDS after reproducing the DTC during troubleshooting. The ECM reset command erases all stored DTC codes, freeze data, on-board snapshot, readiness codes, and all specific data to correct the system except CKP pattern. If the CKP pattern data in the ECM was cleared, you must do the CKP pattern learn procedure. The CKP pattern clear command erases only CKP pattern data. This command is for repair of a misfire or the CKP sensor.

Learn Procedure (without the HDS)

  1. Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on.
  2. Test-drive the vehicle on a level road: Decelerate (with the throttle fully closed) from an engine speed of 2,500 RPM down to 1,000 RPM with the transmission in 1st.
  3. Test-drive the vehicle on a level road: Decelerate (with the throttle fully closed) from an engine speed of 5,000 RPM down to 3,000 RPM with the transmission in 1st.
  4. Repeat step 2 and 3 several times.
  5. Turn the ignition switch to LOCK (0).
  6. Turn the ignition switch to ON (II), and wait 30 seconds.

Substituting the ECM

Special Tools Required

  1. Honda diagnostic system (HDS) tablet tester
  2. Honda interface module (HIM) and an iN workstation with the latest HDS software version
  3. HDS pocket tester
  4. GNA600 and an iN workstation with the latest HDS software version

Any one of the above updating tools can be used.

Note. Use this procedure when you have to substitute a known-good ECM during troubleshooting procedures.

Scheme 956

Scheme 956

Scheme 957

Scheme 957

Scheme 958

Scheme 958
  1. Connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
  2. Turn the ignition switch to ON (II).
  3. Make sure the HDS communicates with the ECM and other vehicle systems. If it doesn't, go to the DLC circuit troubleshooting (see «DLC CIRCUIT TROUBLESHOOTING»(ref-355119-S04276123312010012000000) ). If you are returning from DLC circuit troubleshooting, skip steps 4 and 5, then clean the throttle body after substituting the ECM (see «THROTTLE BODY CLEANING»(ref-255502-S05877419632007060300000) ).
  4. Select the INSPECTION MENU with the HDS.
  5. Select the ETCS TEST, then select the TP POSITION CHECK, and follow the screen prompts. NOTE: If the TP POSITION CHECK indicates FAILED, continue this procedure.
  6. Turn the ignition switch to LOCK (0).
  7. Jump the SCS line with the HDS.
  8. Do the battery removal procedure (see «BATTERY REMOVAL AND INSTALLATION»(ref-255511-S12704431312009112300000) ).
  9. Remove the cover (A).
  10. Remove the bolts (D), then remove the ECM (E).
  11. Disconnect ECM connectors A, B, and C. NOTE: ECM connectors A, B, and C have symbols (A=[], B=delta , C=o) embossed on them for identification.
  12. Install a known-good ECM in the reverse order of removal.
  13. Do the battery installation procedure (see «BATTERY REMOVAL AND INSTALLATION»(ref-255511-S12704431312009112300000) ). NOTE: While doing the battery terminal reconnection procedure, do not start the engine.
  14. Turn the ignition switch to ON (II). NOTE: DTC P0630 VIN Not Programmed or Mismatch may be stored because the VIN has not been programmed into the ECM; ignore it, and continue this procedure.
  15. Manually input the VIN to the ECM with the HDS.
  16. Select the IMMOBI SYSTEM with the HDS.
  17. Enter the immobilizer ECM code that you got from the iN, and use the ECM replacement procedure in the IMMOBI MENU of the HDS; it allows you to start the engine
  18. Reset the ECM with the HDS.
  19. If the TP POSITION CHECK failed in step 5, clean the throttle body (see «THROTTLE BODY CLEANING»(ref-255502-S05877419632007060300000) ).
  20. Update the ECM if it does not have the latest software (see «ECM UPDATE»(ref-355119-S38923566472010012000000) ).
  21. Do the ECM idle learn procedure (see «ECM IDLE LEARN PROCEDURE»(ref-255526-S39475388272007060300000) ).
  22. Do the CKP pattern clear/CKP pattern learn procedure.

OBD Status

The OBD status shows the current system status of each DTC and all of the parameters. This function is used to see if the repair was successfully completed. The results of diagnostic tests for the DTC are displayed as

  1. PASSED: The on board diagnosis is successfully finished.
  2. FAILED: The on board diagnosis has finished but failed.
  3. EXECUTING: The vehicle is in enable criteria conditions of the DTC, and the on board diagnosis is running.
  4. NOT COMPLETED: The on board diagnosis was running but is out of the enable conditions of the DTC.
  5. OUT OF CONDITION: The vehicle has stayed out of the enable conditions of the DTC.

Electronic Control Systems

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

Fail-safe Function

When an abnormality occurs in the signal from a sensor or from another control unit, the ECM ignores that signal and substitute a pre-programmed value that allows the engine to continue running. This causes a Confirmed DTC to be stored and the MIL to come on.

MIL Bulb Check and Readiness Code Condition

When the ignition switch is turned to ON (II), the ECM turns on the MIL via the F-CAN circuit for about 15 to 20 seconds to check the bulb condition. If any readiness codes are not set to complete, the MIL flashes five times. If all readiness codes are set to complete, the MIL goes off.

Self Shut Down (SSD) Mode

After the ignition switch is turned to LOCK (0), the ECM stays on (about 40 minutes). If the ECM connector is disconnected during this time, the ECM 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 to LOCK (0).

Scheme 959

Scheme 959: ECM Inputs and Outputs at ECM Connector A ([]) (44P)
Terminal numberWire colorTerminal nameDescriptionSignal
4BLU (1) PUR (2)FANL (RADIATOR FAN CONTROL)Drives radiator fan relayWith radiator fan running: about 0 V With radiator fan stopped: battery voltage
5GRYFANH (RADIATOR FAN CONTROL)Drives A/C condenser fan relayWith A/C condenser fan running at high speed: about 0 V With A/C condenser fan stopped or running at low speed: battery voltage
6GRNMRLY (PGM-FI MAIN RELAY 1)Drives PGM-FI main relay 1 Power source for DTC memoryWith ignition switch ON (II): about 0 V With ignition switch in LOCK (0): battery voltage
8ORNIGP (POWER SOURCE)Power source for ECM circuitWith ignition switch ON (II): battery voltage
9BLKSG6 (SENSOR GROUND)Sensor groundLess than 0.2 V at all times
10LT GRNVSV (EVAPORATIVE EMISSION (EVAP) CANISTER VENT SHUT VALVE)Drives EVAP canister vent shut valveWith ignition switch ON (II): battery voltage
14REDACC (A/C COMPRESSOR CLUTCH RELAY)Drives A/C compressor clutch relayWith compressor ON: about 0 V With compressor OFF: battery voltage
15BRNIMOFPR (IMMOBILIZER FUEL PUMP RELAY)Drives PGM-FI main relay 2 (FUEL PUMP)About 0 V for 2 seconds after turning ignition switch to ON (II), then battery voltage
16LT GRNACPD (A/C PRESSURE SENSOR)Detects A/C pressure sensor signalWith A/C switch ON: about 1.7-4.8 V (depending on A/C pressure)
17YELAPSA (ACCELERATOR PEDAL POSITION (APP) SENSOR A)Detects APP sensor A signalWith ignition switch ON (II) and accelerator pedal pressed: about 4.7 V With ignition switch ON (II) and accelerator pedal released: about 1.0 V
18PURAPSB (ACCELERATOR PEDAL POSITION (APP) SENSOR B)Detects APP sensor B signalWith ignition switch ON (II) and accelerator pedal pressed: about 2.3 V With ignition switch ON (II) and accelerator pedal released: about 0.5 V
19REDVCC6 (SENSOR VOLTAGE)Provides sensor reference voltageWith ignition switch ON (II): about 5.0 V
20YELETCSRLY (ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) CONTROL RELAY)Drives electronic throttle control system (ETCS) control relayWith ignition switch ON (II): about 0 V (4.0 V momentarily)
21LT BLU (1) PNK (2)SUBRLY (PGM-FI SUBRELAY)Drives PGM-FI subrelayWith ignition switch ON (II): about 0 V
23ORNELD (ELECTRICAL LOAD DETECTOR (ELD))Detects ELD signalWith ignition switch ON (II): about 0.1-4.8 V (depending on electrical load)
24GRYVCC5 (SENSOR VOLTAGE)Provides sensor reference voltageWith ignition switch ON (II): about 5.0 V
25BRNVCC4 (SENSOR VOLTAGE)Provides sensor reference voltageWith ignition switch ON (II): about 5.0 V
26WHT (1) LT GRN (2)FTP (FUEL TANK PRESSURE (FTP) SENSOR)Detects FTP sensor signalWith ignition switch ON (II) and fuel fill cap removed: about 2.5 V
27GRNRVS (REVERSE LOCK SOLENOID)Drives reverse lockout solenoidWith vehicle speed below 9 mph (15 km/h): battery voltage With vehicle speed above 13 mph (20 km/h): about 0 V
28BLUNEP (ENGINE SPEED PULSE)Outputs engine speed pulseWith engine running: pulses
29BLUVSSOUT (VEHICLE SPEED SIGNAL OUTPUT)Sends vehicle speed signalDepending on vehicle speed: pulses
31BRNSCS (SERVICE CHECK SIGNAL)Detects service check signalWith service check signal shorted with the HDS: about 0 V With service check signal opened: about 5.0 V
33GRNECT2 (ENGINE COOLANT TEMPERATURE (ECT) SENSOR 2)Detects ECT sensor 2 signalWith ignition switch ON (II): about 0.1-4.8 V (depending on engine coolant temperature)
34LT BLUSG5 (SENSOR GROUND)Sensor groundLess than 0.2 V at all times
35BLUSG4 (SENSOR GROUND)Sensor groundLess than 0.2 V at all times
36WHTCANH (CAN COMMUNICATION SIGNAL HIGH)Sends communication signalWith ignition switch ON (II): about 2.5 V (pulses)
37REDCAN L (CAN COMMUNICATION SIGNAL LOW)Sends communication signalWith ignition switch ON (II): about 2.5 V (pulses)
39BRNBKSWNC (BRAKE PEDAL POSITION SWITCH)Detects brake pedal position switch signalWith ignition switch ON (II) and brake pedal released: battery voltage With ignition switch ON (II) and brake pedal pressed: about 0 V
40LT GRNBKSW (BRAKE PEDAL POSITION SWITCH)Detects brake pedal position switch signalWith brake pedal released: about 0 V With brake pedal pressed: battery voltage
41LT BLUCRMTCLS (CRUISE CLUTCH PEDAL POSITION SIGNAL)Detects clutch pedal position switch signalWith ignition switch ON (II) and clutch pedal released: about 0 V With ignition switch ON (II) and clutch pedal pressed: battery voltage
42REDWEN (WRITE ENABLE SIGNAL)Detects write enable signalWith ignition switch ON (II): about 0 V
44PNKS-NET5V (SERIAL COMMUNICATION FOR IMMOBILIZER)Sends serial communication signalWith ignition switch ON (II): pulses With key removed from ignition switch: about 1.4 V
(1) 2-door (2) 4-door
(1)2-door
(2)4-door

CONNECTOR TERMINALS DESCRIPTION CHART

Scheme 960

Scheme 960: ECM Inputs and Outputs at ECM Connector B (delta) (44P)
Terminal numberWire colorTerminal nameDescriptionSignal
1BLK/RED (1) BLK (2)PG2 (POWER GROUND)Ground circuit for ECMLess than 0.2 V at all times
3YEL/BLUPCS (EVAPORATIVE EMISSION (EVAP) CANISTER PURGE VALVE)Drives EVAP canister purge valveWith engine running, engine coolant below 140°F (60°C): battery voltage With engine running, engine coolant above 140°F (60°C): duty controlled
4BLK/WHTSO2SHTC (SECONDARY HEATED OXYGEN SENSOR (SECONDARY HO2S) (SENSOR 2) HEATER)Drives secondary HO2S (sensor 2) heaterWith ignition switch ON (II): battery voltage With warmed up engine running: duty controlled
7YEL/REDOPSW (OIL PRESSURE SWITCH)Detects engine oil pressure signalWith ignition switch OFF: about 0 V With engine running: battery voltage
18YELVCC2 (SENSOR VOLTAGE)Provides sensor reference voltageWith ignition switch ON (II): about 5.0 V
23RED/WHTECT1 (ENGINE COOLANT TEMPERATURE (ECT) SENSOR 1)Detects ECT sensor 1 signalWith ignition switch ON (II): about 0.1-4.8 V (depending on engine coolant temperature)
30RED/BLKVG+ (MASS AIR FLOW (MAF) SENSOR +SIDE)Detects MAF sensor signalAt idle with warmed up engine and no electrical load: about 1.1-1.6 V (between VG+ terminal and VG- terminal)
31RED/YELIAT (INTAKE AIR TEMPERATURE (IAT) SENSOR)Detects IAT sensor signalWith ignition switch ON (II): about 0.1-4.0 V (about 1.8 Vat normal operating temperature)
32BLK/BLUVG-(MASS AIR FLOW (MAF) SENSOR-SIDE)Ground for MAF sensor signal
33GRN/BLKSG2 (SENSOR GROUND)Sensor groundLess than 0.2 V at all times
34GRN/YELVTS (ROCKER ARM OIL CONTROL SOLENOID)Drives rocker arm oil control solenoidAt idle: about 0 V
36BLKPG1 (POWER GROUND)Ground circuit for ECMLess than 0.2 V at all times
41WHT/GRNALTC (ALTERNATOR CONTROL)Sends alternator control signalWith warmed up engine running: about 5.0 V (depending on electrical load)
42WHT/BLUALTL (ALTERNATOR L SIGNAL)Detects alternator L signalWith ignition switch ON (II): about 0 V With engine running: battery voltage
43WHT/REDALTF (ALTERNATOR FR SIGNAL)Detects alternator FR signalWith engine running: about 2.6-3.4 V (depending on electrical load)
(1) '06 model (2) '07-11 models
(1)'06 model
(2)'07-11 models

CONNECTOR TERMINALS DESCRIPTION CHART

Scheme 961

Scheme 961: ECM Inputs and Outputs at ECM Connector C (o) (44P)
Terminal numberWire colorTerminal nameDescriptionSignal
1WHTIG1 ETCS (IGNITION SIGNAL ETCS)Detects ignition signalWith ignition switch ON (II): battery voltage
2BLKPGMETCS (POWER GROUND ETCS)Ground circuit for ECMLess than 0.2 V at all times
3GRN/YELETCSM-(THROTTLE ACTUATOR-SIDE)Ground for throttle actuatorWith ignition switch ON (II): about 0 V
4BLU/REDETCSM+ (THROTTLE ACTUATOR +SIDE)Drives throttle actuatorWith ignition switch ON (II): about 0 V
5BRNINJ1 (No. 1 INJECTOR)Drives No. 1 injectorAt idle: duty controlled With ignition switch ON (II): battery voltage
6REDINJ2 (No. 2 INJECTOR)Drives No. 2 injector
7BLUINJ3 (No. 3 INJECTOR)Drives No. 3 injector
8YELINJ4 (No. 4 INJECTOR)Drives No. 4 injector
9WHT/GRNAFSHTC (AIR FUEL RATIO (A/F) SENSOR (SENSOR 1) HEATER CONTROL)Drives A/F sensor (sensor 1) heaterWith ignition switch ON (II): battery voltage With warmed up engine running: about 0 V
11GRN/REDMAP (MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR)Detects MAP sensor signalWith ignition switch ON (II): about 3.0 V At idle: about 1.0 V (depending on engine speed)
12BLUVCC3 (SENSOR VOLTAGE)Provides sensor reference voltageWith ignition switch ON (II): about 5.0 V
13YEL/REDVCC1 (SENSOR VOLTAGE)Provides sensor reference voltageWith ignition switch ON (II): about 5.0 V
14GRN/WHTSG1 (SENSOR GROUND)Sensor groundLess than 0.2 V at all times
15YEL/GRNIGPLS1 (No. 1 IGNITION COIL PULSE)Drives No. 1 ignition coilWith ignition switch ON (II): about 0 V With engine running: pulses
16BLU/REDIGPLS2 (No. 2 IGNITION COIL PULSE)Drives No. 2 ignition coil
17WHT/BLUIGPLS3 (No. 3 IGNITION COIL PULSE)Drives No. 3 ignition coil
18BRNIGPLS4 (No. 4 IGNITION COIL PULSE)Drives No. 4 ignition coil
20RED/BLKTPSA (THROTTLE POSITION (TP) SENSOR A)Detects TP sensor A signalWith throttle fully open: about 3.9 V With throttle fully closed: about 0.9 V
21RED/BLUTPSB (THROTTLE POSITION (TP) SENSOR B)Detects TP sensor B signalWith throttle fully open: about 4.1 V With throttle fully closed: about 1.7 V
22BLU/BLKVTPSW (ROCKER ARM OIL PRESSURE SWITCH)Detects rocker arm oil pressure switch signalWith engine at low speed: about 0 V With engine at high speed: battery voltage
23BLU/WHTVTC (VTC OIL CONTROL SOLENOID VALVE)Drives VTC oil control solenoid valveWith ignition switch ON (II): about 0 V
27WHT/REDSHO2S (SECONDARY HEATED OXYGEN SENSOR (SECONDARY HO2S) (SENSOR 2))Detects secondary HO2S (sensor 2) signalWith throttle fully opened from idle with warmed up engine: about 0.6 V With throttle quickly closed: below 0.4 V
29REDAFS+ (AIR FUEL RATIO (A/F) SENSOR (SENSOR 1) +SIDE)Detects A/F sensor (sensor 1) signal
30RED/YELAFS- (AIR FUEL RATIO (A/F) SENSOR (SENSOR 1) -SIDE)Detects A/F sensor (sensor 1) signal
31GRNCMPB (CAMSHAFT POSITION (CMP) SENSOR B)Detects CMP sensor B signalWith engine running: pulses
32BLU/YELCKP (CRANKSHAFT POSITION (CKP) SENSOR)Detects CKP sensor signalWith engine running: pulses
36BLK/GRNIG1 (IGNITION SIGNAL)Detects ignition signalWith ignition switch ON (II): battery voltage
39GRNSG3 (SENSOR GROUND)Sensor groundLess than 0.2 V at all times
40BRN/YELLG1 (LOGIC GROUND)Ground circuit for ECMLess than 0.2 V at all times
41BLU/WHTCMPA (CAMSHAFT POSITION (CMP) SENSOR A)Detects CMP sensor A signalWith engine running: pulses
42RED/BLUKS(KNOCK SENSOR)Detects knock sensor signalWith engine knocking: pulses
43BLK/WHTNC (OUTPUT SHAFT (COUNTERSHAFT) SPEED SENSOR)Detects output shaft (countershaft) speed sensor signalsWith ignition switch ON (II): pulses With vehicle moving: about 5.0 V (pulses)
44BRN/YELLG2 (LOGIC GROUND)Ground circuit for ECMLess than 0.2 V at all times

CONNECTOR TERMINALS DESCRIPTION CHART

Scheme 962

Scheme 962: ECM Electrical Connections

Scheme 963

Scheme 963

Scheme 964

Scheme 964

Scheme 965

Scheme 965

Scheme 966

Scheme 966

Scheme 967

Scheme 967: ECM Circuit Diagram

Scheme 968

Scheme 968

Scheme 969

Scheme 969

Scheme 970

Scheme 970

Scheme 971

Scheme 971

Scheme 972

Scheme 972

Scheme 973

Scheme 973

Scheme 974

Scheme 974

Scheme 975

Scheme 975

Scheme 976

Scheme 976

PGM-FI System

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

Alternator Control

The alternator signals the ECM during charging. The ECM then controls the voltage generated at the alternator according to the electrical load determined by the electrical load detector (ELD) and the driving mode. This reduces engine load to improve fuel economy.

Air Conditioning (A/C) Compressor Clutch Relay

When the ECM receives a demand for cooling from the A/C system, it delays the compressor from being energized, and enriches the mixture to assure a 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 which varies the duration of fuel injection accordingly.

Scheme 977

Scheme 977: Air Fuel Ratio (A/F) Sensor

Barometric Pressure (BARO) Sensor

The BARO sensor is inside the ECM. It converts atmospheric pressure into a voltage signal that is used by the ECM to modify 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.

Scheme 978

Scheme 978: Camshaft Position (CMP) Sensor B

Crankshaft Position (CKP) Sensor

The CKP sensor detects crankshaft speed, and is used by the ECM to determine ignition timing and timing for fuel injection of each cylinder, and engine misfire detection.

Scheme 979

Scheme 979: Crankshaft Position (CKP) Sensor

Engine Coolant Temperature (ECT) Sensors 1 and 2

ECT sensors 1 and 2 are temperature dependent resistors (thermistors). The resistance decreases as the engine coolant temperature increases.

Scheme 980

Scheme 980: Engine Coolant Temperature (ECT) Sensors 1 and 2

Ignition Timing Control

The ECM contains the memory for basic ignition timing at various engine speeds and manifold absolute pressures. It also adjusts the timing according to engine coolant temperature and intake air temperature.

Injector Timing and Duration

The ECM contains the memory for basic discharge duration at various engine speeds and manifold absolute 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 detects long term malfunctions in the fuel system and sets DTCs (diagnostic trouble codes) if needed.

Knock Sensor

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

Scheme 981

Scheme 981: Knock Sensor

Malfunction Indicator Lamp (MIL) Indication (In relation to Readiness Codes)

The vehicle has certain readiness codes that are part of the on-board diagnostics for the emissions systems. If the vehicle's battery has been disconnected or gone dead, if the DTCs have been cleared, or if the ECM has been reset, these codes are reset. In some states, part of the emissions testing is to make sure these codes are set to complete. If all of them are not set to complete, the vehicle may fail the test, or the test cannot be finished.

To check if the readiness codes are set to complete, turn the ignition switch to ON (II), but do not start the engine. The MIL will come on for 15-20 seconds. If it then goes off, the readiness codes are complete. If it flashes five times, one or more readiness codes are not complete. To set each code, drive the vehicle or run the engine as described in the procedures (see HOW TO SET READINESS CODES ).

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor converts manifold absolute pressure into electrical signals that are sent to the ECM.

Scheme 982

Scheme 982: Manifold Absolute Pressure (MAP) Sensor

Mass Air Flow (MAF) Sensor/Intake Air Temperature (IAT) Sensor

The mass air flow (MAF) sensor/intake air temperature (IAT) sensor contains a hot wire sensor, a cold wire sensor, and a thermistor. It is in the intake air passage. The resistance of the hot wire sensor, the cold wire sensor, and the thermistor changes due to intake air temperature and air flow. The control circuit in the MAF sensor controls the current to keep the hot wire at a set temperature. The current is converted to voltage in the control circuit, then output to the ECM.

Scheme 983

Scheme 983: Mass Air Flow (MAF) Sensor/Intake Air Temperature (IAT) Sensor

Output Shaft (Countershaft) Speed Sensor

This sensor detects countershaft speed.

Scheme 984

Scheme 984: Output Shaft (Countershaft) Speed Sensor

Secondary Heated Oxygen Sensor (Secondary HO2S)

The secondary HO2S detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWO, and sends signals to the ECM. To stabilize its output, the sensor has an internal heater. The ECM compares the HO2S output with the A/F sensor output to determine catalyst efficiency. The secondary HO2S is on the TWC.

Scheme 985

Scheme 985: Secondary Heated Oxygen Sensor (Secondary HO2S)

Electronic Throttle Control System

The throttle is electronically controlled. Refer to the system diagram to see a functional layout of the system.

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

Acceleration control: When the accelerator pedal is pressed, the ECM opens the throttle valve, based on the accelerator pedal position (APP) sensor signal.

Cruise control: The ECM controls the throttle actuator to maintain the 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 which then controls the throttle position.

Scheme 986

Scheme 986: Accelerator Pedal Position (APP) Sensor

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.

Scheme 987

Scheme 987: Throttle Body

Electronic Throttle Control System Diagram

The electronic throttle control system consists of the throttle actuator, throttle position (TP> sensor A/B, accelerator pedal position (APP) sensor A/B, the electronic throttle control system (ETCS) control relay, and the ECM.

Scheme 988

Scheme 988: Electronic Throttle Control System Diagram

VTEC/VTC

  1. The i-VTEC has a variable valve timing control (VTC) mechanism on the intake camshaft in addition to the usual VTEC. This mechanism improves fuel efficiency and reduces exhaust emissions at all levels of engine speed, vehicle speed, and engine load.
  2. The VTEC mechanism changes the valve lift and timing by using more than one cam profile.
  3. The VTC changes the phase of the intake camshaft via oil pressure. It changes the intake valve timing continuously.

Scheme 989

Scheme 989
Driving ConditionVTC ControlDescription
(1) Light-loadBase PositionFor stable combustion the cam angle is retarded, and it reduces the entry of exhaust gas into the cylinder.
(2) Medium/high-loadAdvance ControlCam phase angle is controlled to optimize valve timing, improving fuel efficiency, and reduce emissions.
(3) High speedAdvance-Base PositionTo reduce pumping loss, the intake valve is closed quickly. This gives a charging effect to the air/fuel mixture, maximizing engine power.

FUEL EFFICIENCY AND ENGINE LOAD DESCRIPTION CHART

VTC System

  1. The VTC system makes continuous intake valve timing changes based on operating conditions.
  2. Intake valve timing is optimized to allow the engine to produce maximum power.
  3. Cam angle is advanced to obtain the desired EGR effect and reduce pumping loss. The intake valve is closed quickly to reduce the entry of the air/fuel mixture into the intake port and improve the charging effect.
  4. The system reduces the cam advance at idle, stabilizes combustion, and reduces engine speed.
  5. If a malfunction occurs, the VTC system control is disabled and the valve timing is fixed at the fully retarded position.

Scheme 990

Scheme 990

VTEC System

  1. The VTEC system changes the cam profile to correspond to the engine speed. It maximizes torque at low engine speed and output at high engine speed.
  2. The low lift cam is used at low engine speeds, and the high lift cam is used at high engine speeds.

Scheme 991

Scheme 991

Scheme 992

Scheme 992: VTC System Diagram

Camshaft Position (CMP) Sensor A

CMP sensor A detects camshaft angle position for the VTC system.

Scheme 993

Scheme 993: Camshaft Position (CMP) Sensor A

Idle Control System

When the engine is cold, if 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 sends signals to the throttle position to maintain the correct idle speed.

Brake Pedal Position Switch

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

Electrical Power Steering (EPS) Signal

The EPS signals the ECM when the power steering load is high.

Fuel Cutoff Control

During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at engine speeds over 1,150 RPM. Fuel cutoff control also occurs when the engine speed exceeds 8,200 RPM, regardless of the position of the throttle valve, to protect the engine from over-revving. When the vehicle is stopped, the ECM cuts the fuel at engine speeds over 7,700 RPM. On a cold engine, fuel cut occurs at a lower engine speed.

Fuel Pump Control

When the ignition switch is turned to ON (II), the ECM grounds PGM-FI main relay 2 (FUEL PUMP) which feeds current to the fuel pump for 2 seconds to pressurize the fuel system. When the engine starts, the ECM grounds PGM-FI main relay 2 (FUEL PUMP) and feeds current to the fuel pump. When the engine is not running and the ignition switch is turned to ON (II), the ECM cuts ground to PGM-FI main relay 2 (FUEL PUMP) which cuts current to the fuel pump.

PGM-FI Main Relays 1 and 2

PGM-FI main relay 1 is energized whenever the ignition switch is turned to ON (II) to supply battery voltage to the ECM, power to the injectors, and power for PGM-FI main relay 2 (FUEL PUMP). PGM-FI main relay 2 (FUEL PUMP) is energized to supply power to the fuel pump for 2 seconds when the ignition switch is turned to 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.

Scheme 994

Scheme 994: Intake Air Bypass Control Thermal Valve

Three Way Catalytic Converter {TWO

The TWC converts hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to carbon dioxide (CO 2 ), nitrogen (N2), and water vapor.

Scheme 995

Scheme 995: Three Way Catalytic Converter {TWO

Positive Crankcase Ventilation (PCV) System

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

Scheme 996

Scheme 996: Positive Crankcase Ventilation (PCV) System

Evaporative Emission (EVAP) Control System

Refer to the system diagram to see a 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.

EVAP Canister Purge Valve

When the engine coolant temperature is below 140°F (60°C), the ECM turns off the EVAP canister purge valve which cuts vacuum to the EVAP canister.

Scheme 997

Scheme 997: EVAP Canister Purge Valve

Fuel Tank Pressure (FTP) Sensor

The FTP sensor converts fuel tank absolute pressure into an electrical input to the ECM.

Scheme 998

Scheme 998: Fuel Tank Pressure (FTP) Sensor

EVAP Canister Vent Shut Valve

The EVAP canister vent shut valve is on the EVAP canister.

The EVAP canister vent shut valve controls the venting of the EVAP canister.

Scheme 999

Scheme 999: EVAP Canister Vent Shut Valve

Evaporative Emission (EVAP) Control Diagram

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

The EVAP canister is purged by drawing fresh air through it and into a port on the intake manifold.

The purging vacuum is controlled by the EVAP canister purge valve, which operates whenever engine coolant temperature is above 140°F (60°C).

Scheme 1000

Scheme 1000: Evaporative Emission (EVAP) Control Diagram

Fuel Cap Warning Message

The ECM detects a loose or missing fuel fill cap as an evaporative system leak, and alerts the driver by showing a warning message in the gauge display.

First drive cycle

The first time a leak is detected, a CHECK FUEL CAP message is shown in the gauge display (A). To scroll to another message, press the select/reset button. The CHECK FUEL CAP message appears each time you restart the engine until the system turns the message off. Turn the engine off, then replace or tighten the fuel fill cap until clicks at least once.

Scheme 1001

Scheme 1001: First drive cycle

Procedure

  1. Tighten the fuel fill cap until it clicks.
  2. Clear the Pending DTC with the HDS.
  3. Verify there is no leak by doing the EVAP FUNCTION TEST in the INSPECTION MENU with the HDS.
  1. Tighten the fuel fill cap until it clicks.
  2. The message should go off after several days of normal driving.
  1. Tighten the fuel fill cap until it clicks.
  2. Start the engine, then turn the ignition switch to LOCK (0).
  3. Repeat step 2 two more times.

The vehicle has certain readiness codes that are part of the on-board diagnostics for the emissions systems. If the vehicle's battery has been disconnected or gone dead, if DTCs have been cleared, or if the ECM has been reset, these readiness codes are reset to incomplete. In some states, part of the emissions testing is to make sure these codes are set to complete. If all of them are not set to complete, the vehicle may fail the emission test, or the test cannot be finished.

To check if the readiness codes are set to complete, turn the ignition switch to ON (II), but do not start the engine. The MIL comes on for 15-20 seconds. If it then goes off, the readiness codes are set to complete. If it flashes five times, one or more readiness codes are not set to complete. To set readiness codes from incomplete to complete, do the procedure for the appropriate code.

To check the status of a specific DTC system, check the OBD status in the DTC MENU with the HDS (see OBD STATUS ). This screen displays the DTC, the current data list of the enable criteria, and the status of the readiness testing.

Catalytic Converter Monitor and Readiness Code

Note. During the procedure, do not turn the ignition switch to ACC (I) or LOCK (0). All readiness codes are cleared when the battery is disconnected, if DTCs have been cleared, or if the ECM is reset with the HDS. Low ambient temperatures or excessive stop-and-go traffic may increase the drive time needed to switch the readiness code from incomplete to complete. The readiness code will not switch to complete until all the enable criteria are met. If a fault in the secondary HO2S system caused the MIL to come on, the readiness code cannot be set to complete until you correct the fault.

Enable Criteria

  1. ECT SENSOR 1 at 158°F (70°C) or more.
  2. IAT SENSOR at 20°F (-7°C) or more.
  3. Vehicle speed above 25 mph (40 km/h).
  1. Connect the HDS to the vehicle's data link connector (DLC), and bring up the READINESS CODEs screen for Catalyst in the DTCs MENU.
  2. Start the engine.
  3. Test-drive the vehicle under stop-and-go conditions with short periods of steady cruise. After about 5 miles (8 km), the readiness code should switch to complete.
  4. If the readiness code is still not set to complete, check for a Pending DTC with the HDS. If there is no DTC, one or more of the enable criteria were probably not met; repeat the procedure.

Evaporative Emission (EVAP) Control System Monitor and Readiness Code

Note. All readiness codes are cleared when the battery is disconnected, if DTCs have been cleared, or if the ECM is reset with the HDS.

  1. Battery voltage is more than 10.5 V.
  2. Engine at idle.
  3. ECT SENSOR 1 and SENSOR 2 between 176°F (80°C) and 212°F (100°C).
  4. MAP sensor less than 46.6 kPa (14 inHg, 350 mmHg).
  5. Vehicle speed 0 mph (0 km/h).
  6. IAT SENSOR between 32°F (0°C) and 212°F (100°C).
  1. Connect the HDS to the DLC.
  2. Start the engine.
  3. Select EVAP TEST in the INSPECTION MENU with the HDS, then select the FUNCTION TEST in the EVAP TEST MENU. If the result is normal, readiness is complete. If the result is not normal, go to the next step.
  4. Check for a Pending DTC. If there is no DTC, one or more of the enable criteria were probably not met; repeat the procedure.

Air Fuel Ratio (A/F) Sensor Monitor and Readiness Code

Note. During the procedure, do not turn the ignition switch to ACC (I) or LOCK (0). All readiness codes are cleared when the battery is disconnected, if the DTCs have been cleared, or if the ECM is reset with the HDS.

ECT SENSOR 1 at 140°F (60°C) or more.

  1. Start the engine.
  2. Test-drive the vehicle under stop-and-go conditions with short periods of steady cruise. During the drive, decelerate (with the throttle fully closed) for 5 seconds. After about 3.5 miles (5.6 km), the readiness code should switch from incomplete to complete.
  3. Check the readiness codes screen for the AIR FUEL RATIO (A/F) SENSOR in the DTCs MENU with the HDS. If the screen shows complete, readiness is complete. If the screen shows not complete, go to the next step.
  4. Check for a Pending DTC. If there is no DTC, the enable criteria was probably not met. Select the DATA LIST MENU. Check the ECT SENSOR 1 in the ALL DATA LIST with the HDS. If the ECT SENSOR 1 is less than 140°F (60°C), run the engine until it is more than 140°F (60°C), then repeat the procedure.

Air Fuel Ratio (A/F) Sensor Heater Monitor Readiness Code

Note. All readiness codes are cleared when the battery is disconnected, if DTCs have been cleared, or if the ECM is reset with the HDS.

  1. Start the engine, and let it idle for 1 minute. The readiness code should switch from incomplete to complete.
  2. If the readiness code is still not set to complete, check for a Pending DTC. If there is no DTC, repeat the procedure.

Misfire Monitor and Readiness Code

  1. This readiness code is always set to available because misfiring is continuously monitored.
  2. Monitoring pauses, and the misfire counter resets, if the vehicle is driven over a rough road.
  3. Monitoring also pauses, and the misfire counter holds at its current value, if the throttle position changes more than a predetermined value, or if driving conditions fall outside the range of any related enable criteria.

Fuel System Monitor and Readiness Code

  1. This readiness code is always set to available because the fuel system is continuously monitored during closed loop operation.
  2. Monitoring pauses when the catalytic converter, EVAP control system, and A/F sensor monitors are active.
  3. Monitoring also pauses when any related enable criteria are not being met. Monitoring resumes when the enable criteria is again being met.

Comprehensive Component Monitor and Readiness Code

This readiness code is always set to available because the comprehensive component monitor is continuously running whenever the engine is cranking or running.