The Throttle Position (TP) sensor is mounted on the throttle body, and detects the opening angle of the throttle valve. This sensor is a non-contact type, and uses Hall-effect elements, in order to yield accurate signals, even in extreme driving conditions, such as at high speeds as well as very low speeds.

The TP sensor has two sensor circuits which each transmits a signal, VTA1 and VTA2. VTA1 is used to detect the throttle valve angle and VTA2 is used to detect malfunctions in VTA1. The sensor signal voltages vary between 0 V and 5 V in proportion to the throttle valve opening angle, and are transmitted to the VTA terminals of the ECM.

As the valve closes, the sensor output voltage decreases and as the valve opens, the sensor output voltage increases. The ECM calculates the throttle valve opening angle according to these signals and controls the throttle actuator in response to driver inputs. These signals are also used in calculations such as air-fuel ratio correction, power increase correction and fuel-cut control.

Dtc P0120 Throttle / Pedal Position Sensor / Switch A Circuit Malfunction. 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

DTC No.	DTC Detection Condition	Trouble Area
P0120	Output voltage of VTA1 quickly fluctuates beyond lower and upper malfunction thresholds for 2 seconds (1 trip detection logic)	Throttle Position (TP) sensor (built into throttle body) ECM
P0122	Output voltage of VTA1 0.2 V or less for 2 seconds (1 trip detection logic)	TP sensor (built into throttle body) Short in VTA1 circuit Open in VC circuit ECM
P0123	Output voltage of VTA1 4.535 V or more for 2 seconds (1 trip detection logic)	TP sensor (built into throttle body) Open in VTA1 circuit Open in E2 circuit Short between VC and VTA1 circuits ECM
P0220	Output voltage of VTA2 quickly fluctuates beyond lower and upper malfunction thresholds for 2 seconds (1 trip detection logic)	TP sensor (built into throttle body) ECM
P0222	Output voltage of VTA2 1.75 V or less for 2 seconds (1 trip detection logic)	TP sensor (built into throttle body) Short in VTA2 circuit Open in VC circuit ECM
P0223	Output voltage of VTA2 4.8 V or more, and VTA1 between 0.2 V and 2.02 V, for 2 seconds (1 trip detection logic)	TP sensor (built into throttle body) Open in VTA2 circuit Open in E2 circuit Short between VC and VTA2 circuits ECM
P2135	Either condition (a) or (b) met (1 trip detection logic): (a) Difference between output voltages of VTA1 and VTA2 0.02 V or less for 0.5 seconds or more (b) Output voltage of VTA1 0.2 V or less, and VTA2 1.75 V or less, for 0.4 seconds or more	Short between VTA1 and VTA2 circuits TP sensor (built into throttle body) ECM

HINT:

When any of these DTCs are set, check the throttle valve opening angle by entering the following menus on an intelligent tester: Power train / Engine / Data List / Throttle Sensor Position and Throttle Position No. 2.

THROTTLE POS denotes the VTA1 signal (expressed in percentages), and THROTTLE POS #2 denotes the VTA2 signal (expressed in voltages).

Reference (Normal Condition):
Tester Display	Accelerator Pedal Fully Released	Accelerator Pedal Fully Depressed
THROTTLE POS	10 to 24 %	64 to 96 %
THROTTLE POS #2	2.1 to 3.1 V	4.5 to 5.0 V

FAIL-SAFE

When any of these DTCs, as well as other DTCs relating to ETCS (Electronic Throttle Control System) malfunctions, are set, the ECM enters fail-safe mode. During the ECM cuts the current to the throttle actuator off, and the throttle valve is returned to a 6° throttle angle by the return spring. The ECM then adjusts the engine output by controlling the fuel injection (intermittent fuel-cut) and ignition timing, in accordance with the accelerator pedal opening angle, to allow the vehicle to continue at a minimal speed. If the accelerator pedal is depressed firmly and gently, the vehicle can be driven slowly.

WIRING DIAGRAM

Dtc P0120 Throttle / Pedal Position Sensor / Switch A Circuit Malfunction. 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

INSPECTION PROCEDURE

HINT:

If other DTCs relating to different systems that have terminal E3 as the ground terminal are output simultaneously, terminal E3 may have an open circuit.

Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred .

These DTCs relate to the Throttle Position (TP) sensor.

1.READ VALUE OF THROTTLE POSITION SENSOR (THROTTLE POS AND THROTTLE POS #2)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) and turn the intelligent tester ON.

Enter the following menus: Power train / Engine / Data List / Throttle Sensor Position and Throttle Position No. 2.

Check the values displayed on the tester.

Result:

TP#1 (VTA1) When AP Released	TP#2 (VTA2) When AP Released	TP#1 (VTA1) When AP Depressed	TP#2 (VTA2) When AP Depressed	Trouble Area	Proceed to
0 %	Between 0 V and 0.2 V	0 %	Between 0 V and 0.2 V	VC circuit open	A
100 %	Between 4.5 V and 5.0 V	100 %	Between 4.5 V and 5.0 V	E2 circuit open	A
0 % or 100 %	Between 2.1 V and 3.1 V (Fail-safe)	0 % or 100 %	Between 2.1 V and 3.1 V (Fail-safe)	VTA1 circuit open or ground short	A
Approx 19 % (Fail-safe)	Between 0 V and 0.2 V, or 4.5 V and 5.0 V	Between 10 % and 24 % (Fail-safe)	Between 0 V and 0.2 V, or 4.5 V and 5.0 V	VTA2 circuit open or ground short	A
Between 10 % and 24 %	Between 2.1 V and 3.1 V	Between 64 % and 96 % (Not fail-safe)	Between 4.5 V and 5.0 V (Not fail-safe)	TP sensor circuit normal	B

HINT:

TP#1 denotes THROTTLE POS, and TP#2 denotes THROTTLE POS#2.

AP denotes Accelerator Pedal.

VTA1 is expressed as percentages, and VTA2 is expressed as voltages.

Go to step 5

A

2.CHECK HARNESS AND CONNECTOR (THROTTLE POSITION SENSOR - ECM)

Dtc P0120 Throttle / Pedal Position Sensor / Switch A Circuit Malfunction. 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

Disconnect the E17 throttle body connector.

Disconnect the E3 and E5 ECM connectors.

Measure the resistance of the wire harness side connector.

Standard resistance (Check for open):
Tester Connection Specified Condition
VC (E17-5) - VC2 (E5-29) Below 1 Ω
VTA (E17-6) - VTA1 (E3-23) Below 1 Ω
VTA2 (E17-4) - VTA2 (E3-22) Below 1 Ω
E2 (E17-3) - E3 (E5-30) Below 1 Ω

Standard resistance (Check for short):

Tester Connection	Specified Condition
VC (E17-5) or VC2 (E5-29) - Body ground	10 kΩ or higher
VTA (E17-6) or VTA1 (E3-23) - Body ground	10 kΩ or higher
VTA2 (E17-4) or VTA2 (E3-22) - Body ground	10 kΩ or higher

Reconnect the throttle body connector.

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.INSPECT ECM (VC VOLTAGE)

Disconnect the E17 throttle body connector.

Turn the engine switch on (IG).

Measure the voltage of the E5 ECM connector.

Standard voltage:
Tester Connection Specified Condition
VC2 (E5-29) - E3 (E5-30) 4.5 to 5.0 V

Reconnect the throttle body connector.

REPLACE ECM

OK

4.REPLACE THROTTLE BODY

NEXT

5.CHECK WHETHER DTC OUTPUT RECURS (THROTTLE POSITION SENSOR DTCS)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) and turn the tester ON.

Clear DTCs .

Start the engine.

Allow the engine to idle for 15 seconds or more.

Enter the following menus: Power train / Engine / DTC.

Read DTCs.

Result:
Display (DTC Output) Proceed to
P0120, P0122, P0123, P0220, P0223, and/or P2135 A
No output B

SYSTEM IS OK

REPLACE ECM

LEXUS IS250, IS220d / GSE20 ALE20

4GR-FSE ENGINE CONTROL SYSTEM

Lexus IS250 IS220d GSE20 ALE20

SFI SYSTEM

Display (DTC Output)	Proceed to
P0120, P0122, P0123, P0220, P0223, and/or P2135	A
No output	B