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VTC System
VTEC System
K20Z2 engine
K20Z3 engine
11-38
Fuel and Emissions Systems
System Description (cont’d)
MAXIMUM VTC ADVANCE 25 °
TDC
EX IN 1IN 2
EX IN 2IN 1
MAXIMUM VTC ADVANCE 25 °
SHORT OVERLAP
LONG OVERLAP
LOW SPEED VALVE TIMING HIGH SPEED VALVE TIMING
EX IN EXIN
IN (LOW LIFT)
LOW SPEED VALVE TIMING HIGH SPEED VALVE TIMING
EX IN EX IN
The VTC system makes continuous intake valve timing changes based on operating conditions.
Intake valve timing is optimized to allow the engine to produce maximum power.
Cam angle is advanced to obtain the 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.
The system reduces the cam advance at idle, stabilizes combustion, and reduces engine speed.
If a malfunction occurs, the VTC system control is disabled and the valve timing is fixed at the fully retarded position.
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.
The low lift cam is used at low engine speeds, and the high lift cam is used at high engine speeds.
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VTEC/VTC
System Diagram
Camshaft Position (CMP) Sensor A
11-39
VTC
RETARD
CHAMBERFrom No. 3
ALTERNATOR
(10 A) FUSE
VARIOUS
SENSORS
ECM/PCM
CMP SENSOR A
INTAKE
CAMSHAFT
VTC
ADVANCE
CHAMBER ADVANCE
RETARD
VANE
VTC ACTUATOR VANE
HOUSING
From
OIL PUMP
VTC OIL CONTROL
SOLENOID VALVE
SPOOL
VALVE
ROCKER ARM
OIL CONTROL
SOLENOID ROCKER
ARM OIL
PRESSURE
SWITCH BLK
BLK GRN/YEL
BLU/BLK BLK/YEL
BLU/WHT BLU/WHT YEL
BRN/YEL
BLK
BRN/YEL
VTC STRAINERO-RING
MAGNET
TERMINAL
DRAIN
DRAIN
CMP sensor A detects camshaft angle position for the VTC system.
(cont’d)
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Page 363 of 2893

Intake Air System
Catalytic Converter System
Positive Crankcase Ventilation (PCV) System
Intake Air Bypass Control Thermal Valve Three Way Catalytic Converter (TWC)
11-40Fuel and Emissions Systems
System Description (cont’d)
OUT
INVALVE
WAX
ELEMENT
INJECTOR INTAKE AIR
BYPASS CONTROL
THERMAL VALVE FRONT OF
VEHICLE
HOUSING
THREE WAY
CATALYST BREATHER PIPE
INTAKE
MANIFOLD
PCV HOSE PCV VALVE
:BLOW-BYVAPOR
:FRESHAIR
This system supplies air for engine needs.
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. The TWC converts hydrocarbons (HC), carbon
monoxide (CO), and oxides of nitrogen (NOx) in the
exhaust gas to carbon dioxide (CO ), nitrogen (N ), and
water vapor.
The PCV valve prevents blow-by gasses from escaping
into the atmosphere by venting them into the intake
manifold.
22
* : This illustration shows K20Z2 engine
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Page 364 of 2893

Exhaust Gas Recirculation (EGR) System
(K20Z2 engine)
Evaporative Emission (EVAP) Control
System
EGR Valve
EVAP Canister
EVAP Canister Purge Valve
Fuel Tank Pressure (FTP) Sensor
EVAP Canister Vent Shut Valve
11-41
TERMINAL
COIL
OUT
IN O-RING
TERMINAL
SENSOR UNIT
O-RING VALVE O-RING TERMINAL
Refer to the system diagram to see a functional layout
of the system.
The EGR valve lowers peak combustion temperatures
and reduces oxides of nitrogen emissions (NOx) by
recirculating exhaust gas through the intake manifold
and into the combustion chambers.
Refer to the system diagram to see a functional layout
of the system.
The EVAP canister temporarily stores fuel vapor from
the fuel tank until it can be purged back into the engine
and burned.
When the engine coolant temperature is below 60 °C
(140 °F), the ECM/PCM turns off the EVAP canister
purge valve which cuts vacuum to the EVAP canister. The FTP sensor converts fuel tank absolute pressure
into an electrical input to the ECM/PCM.
The EVAP canister vent shut valve is on the EVAP
canister.
The EVAP canister vent shut valve controls the venting
of the EVAP canister.
(cont’d)
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Page 365 of 2893

Î
Fuel Cap Warning MessageTo make the message go off (with the HDS)
To make the message go off (without the
HDS) (’06 model)
To make the message go off (without the
HDS) (’07-09 models)
First drive cycle Procedure
Procedure
Procedure
11-42Fuel and Emissions Systems
System Description (cont’d)
A
Shows CHECK FUEL CAP
in the gauge display.
The ECM/PCM detects a loose or missing fuel fill cap as
an evaporative system leak, and alarts the driver by
showing a warning message in the gauge display.
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 it clicks at least once.
1. Tighten the fuel fill cap until it clicks.
2. Clear the Temporary 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 s everal 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.
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Electronic Throttle Control System Diagram
11-43
TP SENSOR A
TP SENSOR B THROTTLE
ACTUATOR
THROTTLE
BODY
From
ETCS CONTROL
RELAY
VARIOUS
SENSORS
ECM/
PCM
APP
SENSOR A
APP
SENSOR B BRN
YEL
BLU
PUR
LT BLU GRY
BLK YEL
GRN
RED/BLU BLUBLU/RED
GRN/YEL
RED/BLK
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/PCM.
(cont’d)
* : This illustration shows K20Z2 engine
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Î
Exhaust Gas Recirculation (EGR) System Diagram (K20Z2 engine)
11-44Fuel and Emissions Systems
System Description (cont’d)
INTAKE MANIFOLD
EGR VALVE
EGR VALVE
POSITION SENSOR
YEL/BLU
GRN/BLK
WHT/BLK
BLU/RED
BLK/RED
(BLK)
BLK
ECM/PCM
VARIOUS
SENSORS
* : ’07-09 models
*
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.
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Page 368 of 2893
Î
Evaporative Emission (EVAP) Control Diagram
11-45
ATMOSPHERE
ATMOSPHERE
FUEL FILL
CAP FUEL TANK VAPOR
RECIRCULATION
TUBE
FUEL TANK VAPOR
CONTROL VALVE
VARIOUS
SENSORS
FUEL TANK FTP SENSOR
EVAP CANISTER
VENT SHUT VALVE
PUR
LT GRN
ECM/PCM BLK
YEL
YEL/BLU
BLK/YEL RED
BLU BLK
LT GRN
From
No. 3
ALTERNATOR
(10 A) FUSE
From
PGM-FI
SUBRELAY
EVAP
CANISTER
EVAP CANISTER
PURGE VALVE ATMOSPHERE
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 60 °C (140 °F).
(cont’d)
* : This illustration shows K20Z2 engine
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