Acura TSX / Honda Accord CL. Manual - part 565

Fig. 51: High Speed Valve Timing 

VTEC/VTC 

Fig. 52: VTEC/VTC System Wiring Diagram 

CAMSHAFT POSITION (CMP) SENSOR A 

This sensor detects camshaft angle position for the VTC system.

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 53: Cutaway View Of Camshaft Position (CMP) Sensor A 

IDLE CONTROL SYSTEM 

When the engine is cold, the A/C compressor is on, the transmission is in gear, the brake pedal is pressed, the 
power steering load is high, or the alternator is charging, the ECM/PCM controls current to the throttle actuator 
to maintain the correct idle speed. 

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

BRAKE PEDAL POSITION SWITCH 

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

POWER STEERING PRESSURE (PSP) SWITCH 

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

FUEL SUPPLY SYSTEM 

Fuel Cut-off Control 

During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at 
engine speeds over 1,000 RPM. Fuel cut-off control also occurs when the engine speed exceeds 7,300 RPM, 
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 5,000 RPM (M/T: 4,500 RPM). Engine speed of 
fuel cut is lower on a cold engine. 

Fuel Pump Control 

When the ignition is turned on, the ECM/PCM grounds the PGM-FI main relay which feeds current to the fuel 
pump for 2 seconds to pressurize the fuel system. With the engine running, the ECM/PCM grounds the PGM-FI 
main relay and feeds current to the fuel pump. When the engine is not running and the ignition is on, the 
ECM/PCM cuts ground to the PGM-FI main relay which cuts current to the fuel pump. 

PGM-FI MAIN RELAY 1 & 2 

The PGM-FI relay consists of two separate relays. PGM-FI main relay 1 (FI MAIN) is energized whenever the 
ignition switch is ON (II) to supply battery voltage to the ECM/PCM, power to the injectors, and power for 
PGM-FI main relay 2 (FUEL PUMP). PGM-FI main relay 2 is energized to supply power to the fuel pump for 2 
seconds when the ignition switch is turned ON (II), and when the engine is cranking or running. 

INTAKE AIR SYSTEM 

This system supplies air for engine needs. 

Intake Air Bypass Control Thermal Valve 

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

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 54: Locating Intake Air Bypass Control Thermal Valve 

Resonator 

A resonator in the intake air duct provides additional silencing as air is drawn into the engine. 

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), nitrogen (N2), and water vapor.

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX