Circuit Description

WARNING: This page is about a different car, the 2004 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.

The throttle position sensor is mounted in the throttle body and detects the throttle valve opening angle.

When the throttle valve is fully closed, a voltage of approximately 0.3 to 1.0 V is applied to terminal VTA of the ECM. The voltage applied to terminal VTA of the ECM increases in proportion to the opening angle of the throttle valve and becomes approximately 3.2 to 4.9 V when the throttle valve is fully opened. The ECM judges the vehicle driving conditions from these signals input from terminal VTA, uses them as one of the conditions for deciding the air-fuel ratio correction, power increase correction and fuel-cut control etc.

Fig 1: Throttle/Pedal Position Circuit Description

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DTC DETECTION CONDITION

DTC No.	DTC Detection Condition	Trouble Area
Condition (a) of DTC P0120, P0122 or P0123 continues for 5 seconds (Open or short in throttle position sensor circuit)		Trouble Area
P0120	Detection conditions for DTCs P0122 and P0123 are not satisfied but condition (a) is satisfied VTA less than 0.1 V or VTA more than 4.9 V	Open or short in throttle position sensor circuit Throttle position sensor (built in throttle body) ECM
P0122	VTA stays less than 0.1 V for 5 seconds or more	Throttle position sensor (built in throttle body) Short in VTA circuit Open in VC circuit ECM
P0123	VTA stays more than 4.9 V for 5 seconds or more	Throttle position sensor (built in throttle body) Open in VTA circuit Open in E2 circuit VC and VTA circuit are short-circuited ECM

HINT:

After confirming DTCs, confirm the throttle valve opening percentage and closed throttle position switch condition using the hand-held tester or the OBD II scan tool.

THROTTLE VALVE OPENING POSITION

Throttle valve opening position expressed as percentage		Trouble Area
Throttle valve fully closed	Throttle valve fully open	Trouble Area
0%	0%	VC circuit open VTA circuit open or short
Approx. 100%	Approx. 100%	E2 circuit open