2Az-Fe Engine Control. Dtc P0120 Throttle / Pedal Position Sensor / Switch A Circuit Malfunction

The throttle position sensor is mounted on the throttle body, and detects the opening angle of the throttle valve. This sensor is a non-contact type. It uses Hall-effect elements in order to yield accurate signals even in extreme conditions.
The throttle position sensor has 2 sensor circuits, each of which 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 enrichment correction and fuel-cut control.

Corolla. Zre142 Aze141.2Az-Fe Engine Control.Sfi System.
Dtc
P0120 Throttle / Pedal Position Sensor / Switch A Circuit Malfunction

DTC No.	DTC Detection Condition	Trouble Area
P0120	Output voltage of VTA1 quickly fluctuates beyond lower and upper malfunction thresholds for 2 seconds or more (1 trip detection logic)	Throttle position sensor (built into throttle body) ECM
P0121	Difference between VTA1 and VTA2 voltages less than 0.8 V, or more than 1.6 V for 2 seconds (1 detection logic)	Throttle position sensor (built into throttle body) Throttle position sensor circuit ECM
P0122	Output voltage of VTA1 0.2 V or less for 2 seconds or more (1 trip detection logic)	Throttle position sensor (built into throttle body) Short in VTA1 circuit Open in VCTA circuit ECM
P0123	Output voltage of VTA1 4.54 V or more for 2 seconds or more (1 trip detection logic)	Throttle position sensor (built into throttle body) Open in VTA1 circuit Open in ETA circuit Short between VCTA and VTA1 circuits ECM
P0220	Output voltage of VTA2 quickly fluctuates beyond lower and upper malfunction thresholds for 2 seconds or more (1 trip detection logic)	Throttle position sensor (built into throttle body) ECM
P0222	Output voltage of VTA2 1.75 V or less for 2 seconds or more (1 trip detection logic)	Throttle position sensor (built into throttle body) Short in VTA2 circuit Open in VCTA 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 or more (1 trip detection logic)	Throttle position sensor (built into throttle body) Open in VTA2 circuit Open in ETA circuit Short between VCTA 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 Throttle position 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: Powertrain / Engine and ECT / Data List / Gas Throttle / Throttle Position No. 1 and Throttle Position No. 2.

Throttle Position No. 1 denotes the VTA1 signal, and Throttle Position No. 2 denotes the VTA2 signal.

Reference (Normal Condition):

Techstream Display
Accelerator Pedal Fully Released
Accelerator Pedal Fully Depressed
Throttle Position No. 1
0.5 to 1.1 V
3.2 to 4.8 V
Throttle Position No. 2
2.1 to 3.1 V
4.6 to 4.98 V

MONITOR DESCRIPTION

The ECM uses the throttle position sensor to monitor the throttle valve opening angle. There are several checks that the ECM performs to confirm the proper operation of the throttle position sensor.

P0120, P0122, P0123, P0220, P0222, P0223 and P2135:

A specific voltage difference is expected between the sensor terminals, VTA1 and VTA2, for each throttle valve opening angle. If the difference between VTA1 and VTA2 is incorrect, the ECM interprets this as a malfunction in the sensor circuit, and stores a DTC.
VTA1 and VTA2 each have a specific voltage range. If VTA1 or VTA2 is outside the normal operating range, the ECM interprets this as a malfunction in the sensor circuit, and stores a DTC.
VTA1 and VTA2 should never be close to the same voltage level. If VTA1 is within 0.02 V of VTA2, the ECM determines that there is a short circuit in the sensor circuit, and stores a DTC.

P0121:

This sensor transmits two signals: VTA1 and VTA2. VTA1 is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA1. The ECM performs several checks to confirm the proper operation of the throttle position sensor and VTA1.
For each throttle opening angle, a specific voltage difference is expected between the outputs of VTA1 and VTA2. If the output voltage difference between the two signals deviates from the normal operating range, the ECM interprets this as a malfunction in the throttle position sensor. The ECM illuminates the MIL and stores the DTC.

MONITOR STRATEGY

Related DTCs	P0120: Throttle position sensor 1 range check (Chattering) P0121: Throttle position sensor rationality P0122: Throttle position sensor 1 range check (Low voltage) P0123: Throttle position sensor 1 range check (High voltage) P0220: Throttle position sensor 2 range check (Chattering) P0222: Throttle position sensor 2 range check (Low voltage) P0223: Throttle position sensor 2 range check (High voltage) P2135: Throttle position sensor range check (Correlation)
Required Sensors/Components (Main)	Throttle position sensor
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	2 seconds: P0120, P0122, P0123, P0220, P0222 and P0223 Within 2 seconds: P0121 0.5 seconds: P2135 (Case 1) 0.4 seconds: P2135 (Case 2)
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

P0120, P0122, P0123, P0220, P0222, P0223, P2135
Monitor runs whenever following DTCs not present	None
Either of the following conditions A or B are met	-
A. Ignition switch ON	0.012 seconds or more
B. Electronic throttle actuator power	On

P0121
Monitor runs whenever following DTCs not present	None
Either of following conditions A or B is met	-
A. Ignition switch	ON
B. Electronic throttle motor power	On
Throttle position sensor malfunction (P0120, P0122, P0123, P0220, P0222, P0223, P2135)	Not detected

TYPICAL MALFUNCTION THRESHOLDS

P0120
VTA1 voltage	0.2 V or less, or 4.54 V or more

P0121
Either of following conditions is met	-
Difference of learned throttle position sensor opener position voltage between VTA2 and VTA1	Higher than 1.6 V
Difference of learned throttle position sensor opener position voltage between VTA2 and VTA1	Lower than 0.8 V

P0122
VTA1 voltage	0.2 V or less

P0123
VTA1 voltage	4.54 V or more

P0220
Either of the following conditions is met	-
A. VTA2 voltage	1.75 V or less
B. VTA2 voltage when VTA1 0.2 V or more, and 2.02 V or less	4.8 V or more

P0222
VTA2 voltage	1.75 V or less

P0223
VTA2 voltage when VTA1 0.2 V or more, and 2.02 V or less	4.8 V or more

P2135 (Case 1)
Difference between VTA1 and VTA2 voltages	0.02 V or less

P2135 (Case 2)
VTA1 voltage	0.2 V or less
VTA2 voltage	1.75 V or less

COMPONENT OPERATING RANGE

All of the following conditions are met	-
VTA1 voltage	Higher than 0.2 V, and less than 4.54 V
VTA2 voltage	Higher than 1.75 V, and less than 4.8 V
Difference between VTA1 and VTA2 voltages	Higher than 0.02 V

CONFIRMATION DRIVING PATTERN

Connect the Techstream to the DLC3.
Turn the ignition switch to ON and turn the Techstream on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the ignition switch off and wait for at least 30 seconds.
Turn the ignition switch to ON and turn the Techstream on [A].
Start the engine.
With the vehicle stationary, fully depress and release the accelerator pedal [B].
Idle the engine for 2 seconds or more [C].
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [D].
Read the pending DTCs.
HINT:
1. If a pending DTC is output, the system is malfunctioning.
2. If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0120, P0121, P0122, P0123, P0220, P0222, P0223 or P2135.

Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

HINT:

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [D] again.

If no pending DTC is output, perform a universal trip and check for permanent DTCs (COROLLA_ZRE142 RM000000PDK0ZBX.html).
HINT:
1. If a permanent DTC is output, the system is malfunctioning.
2. If no permanent DTC is output, the system is normal.

FAIL-SAFE

When any of these DTCs, as well as other DTCs relating to Electronic Throttle Control System malfunctions, are set, the ECM enters fail-safe mode. During fail-safe mode, the ECM cuts the current to the throttle actuator, and the throttle valve is returned to a 6.5° 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 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.
Fail-safe mode continues until a pass condition is detected, and the ignition switch is then turned to off.

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

1.READ VALUE USING TECHSTREAM (THROTTLE POSITION SENSOR)

Connect the Techstream to the DLC3.

Turn the ignition switch to ON.

Turn the Techstream on.

Enter the following menus: Powertrain / Engine and ECT / Data List / Gas Throttle / Throttle Position No. 1 and Throttle Position No. 2.

Read the values displayed on the Techstream.

Result
When Accelerator Pedal Fully Released		When Accelerator Pedal Fully Depressed		Trouble Area	Proceed to
Throttle Position No. 1 (VTA1)	Throttle Position No. 2 (VTA2)	Throttle Position No. 1 (VTA1)	Throttle Position No. 2 (VTA2)	Trouble Area	Proceed to
0 to 0.2 V	0 to 0.2 V	0 to 0.2 V	0 to 0.2 V	VCTA circuit open	A
4.5 to 4.98 V	4.5 to 4.98 V	4.5 to 4.98 V	4.5 to 4.98 V	ETA circuit open
0 to 0.2 V, or 4.5 to 4.98 V	2.1 to 3.1 V (Fail-safe)	0 to 0.2 V, or 4.5 to 4.98 V	2.1 to 3.1 V (Fail-safe)	VTA1 circuit open or ground short
0.6 to 1.4 V (Fail-safe)	0 to 0.2 V, or 4.5 to 4.98 V	0.6 to 1.4 V (Fail-safe)	0 to 0.2 V, or 4.5 to 4.98 V	VTA2 circuit open or ground short
0.5 to 1.1 V	2.1 to 3.1 V	3.2 to 4.8 V (Not fail-safe)	4.6 to 4.98 V (Not fail-safe)	Throttle position sensor circuit normal	B

HINT:

DTC P0121 is stored when the VTA1 and VTA2 output voltages are not consistent with the sensor characteristics. Therefore, check the freeze frame data when this DTC is stored. Use the following formula to confirm the relative differences in voltage.
Characteristic Sensor Output:
VTA2 x 0.8 is approximately equal to VTA1 + 1.11 V
VTA1: Throttle Position No. 1
VTA2: Throttle Position No. 2
If DTC P0121 is output, proceed to "Check Harness And Connector (Throttle Position Sensor - ECM)".

Go to step 5

A

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

Disconnect the throttle body connector.

Disconnect the ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance (Check for Open):

Tester Connection	Condition	Specified Condition
B25-5 (VC) - B31-67 (VCTA)	Always	Below 1 Ω
B25-6 (VTA) - B31-115 (VTA1)	Always	Below 1 Ω
B25-4 (VTA2) - B31-114 (VTA2)	Always	Below 1 Ω
B25-3 (E2) - B31-91 (ETA)	Always	Below 1 Ω

Standard Resistance (Check for Short):

Tester Connection	Condition	Specified Condition
B25-5 (VC) or B31-67 (VCTA) - Body ground	Always	10 kΩ or higher
B25-6 (VTA) or B31-115 (VTA1) - Body ground	Always	10 kΩ or higher
B25-4 (VTA2) or B31-114 (VTA2) - Body ground	Always	10 kΩ or higher

Reconnect the throttle body connector.

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (THROTTLE POSITION SENSOR - ECM)

OK

3.INSPECT ECM (VC VOLTAGE)

Disconnect the throttle body connector.

Turn the ignition switch to ON.

Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection
Condition
Specified Condition
B25-5 (VC) - B25-3 (E2)
Ignition switch ON
4.5 to 5.5 V

Reconnect the throttle body connector.

REPLACE ECM (COROLLA_ZRE142 RM000002WT402ZX.html)

OK

4.REPLACE THROTTLE BODY

Replace the throttle body (COROLLA_ZRE142 RM0000017UC03CX.html).

NEXT

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

Connect the Techstream to the DLC3.

Turn the ignition switch to ON.

Turn the Techstream on.

Clear the DTCs (COROLLA_ZRE142 RM000000PDK0ZBX.html).

Start the engine.

Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result:

Result
Proceed to
P0120, P0121, P0122, P0123, P0220, P0222, P0223 and/or P2135
A
No output
B

END

REPLACE ECM (COROLLA_ZRE142 RM000002WT402ZX.html)

Techstream Display	Accelerator Pedal Fully Released	Accelerator Pedal Fully Depressed
Throttle Position No. 1	0.5 to 1.1 V	3.2 to 4.8 V
Throttle Position No. 2	2.1 to 3.1 V	4.6 to 4.98 V

Result	Proceed to
P0120, P0121, P0122, P0123, P0220, P0222, P0223 and/or P2135	A
No output	B