Acura TSX / Honda Accord CL. Manual - part 563

Fig. 42: Cutaway View Of Secondary Heated Oxygen Sensor (Secondary HO2S) 

ELECTRONIC THROTTLE CONTROL SYSTEM 

The throttle is electronically controlled by the electronic throttle control system. Refer to the System Diagram to 
see the functional layout of the system. 

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

Acceleration Control: When the accelerator pedal is pressed, the ECM/PCM opens the throttle valve 
depending on the accelerator pedal position (APP) sensor signal. 

Cruise Control: The ECM/PCM controls the throttle actuator to maintain 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/PCM.

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 43: Locating Accelerator Pedal Position (APP) Sensor

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 44: Cutaway View Of 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.

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 45: Identifying Throttle Body Components 

VTEC/VTC 

The i-VTEC has a VTC (Variable Valve Timing Control) 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. 

The VTEC mechanism changes the valve lift and timing by using more than one cam profile. 

The VTC changes the phase of the intake camshaft via oil pressure. It changes the intake valve timing 
continuously. 

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX