The APP sensor is mounted on the accelerator pedal bracket and has 2 sensor circuits: VPA (main) and VPA2 (sub). 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 voltage, which is applied to terminals VPA and VPA2 of the ECM, varies between 0.5 V and 4.5 V in proportion to the operating angle of the accelerator pedal (throttle valve). A signal from VPA indicates the actual accelerator pedal opening angle (throttle valve opening angle) and is used for engine control. A signal from VPA2 conveys the status of the VPA circuit and is used to check the APP sensor itself.

The ECM monitors the actual accelerator pedal opening angle (throttle valve opening angle) through the signals from VPA and VPA2, and controls the throttle actuator according to these signals.

Diagnostic trouble code P2123 P2125 P2127 P2128 P2138 3UR-FE Land Cruiser Description

DTC Code	DTC Detection Condition	Trouble Area
P2120	VPA fluctuates rapidly beyond the upper and lower malfunction thresholds for 0.5 seconds or more (1 trip detection logic).	APP sensor ECM
P2122	VPA is 0.4 V or less for 0.5 seconds or more when the accelerator pedal is fully released (1 trip detection logic).	APP sensor Open in VCP1 circuit Open or ground short in VPA circuit ECM
P2123	VPA is 4.8 V or higher for 2.0 seconds or more (1 trip detection logic).	APP sensor Open in EPA circuit ECM
P2125	VPA2 fluctuates rapidly beyond the upper and lower malfunction thresholds for 0.5 seconds or more (1 trip detection logic).	APP sensor ECM
P2127	VPA2 is 1.2 V or less for 0.5 seconds or more when the accelerator pedal is fully released (1 trip detection logic).	APP sensor Open in VCP2 circuit Open or ground short in VPA2 circuit ECM
P2128	Conditions (a) and (b) continue for 2.0 seconds or more (1 trip detection logic): (a) VPA2 is 4.8 V or higher. (b) VPA is between 0.4 V and 3.45 V.	APP sensor Open in EPA2 circuit ECM
P2138	Condition (a) or (b) continues for 2.0 seconds or more (1 trip detection logic): (a) The difference between VPA and VPA2 is 0.02 V or less. (b) VPA is 0.4 V or less and VPA2 is 1.2 V or less.	Short between VPA and VPA2 circuits APP sensor ECM

HINT:

When any of these DTCs is output, check the APP sensor voltage by entering the following menus: Powertrain / Engine and ECT / Data List / ETCS / Accelerator Position No. 1 and Accelerator Position No. 2.

Trouble Area	Accelerator Position No. 1 When AP Released	Accelerator Position No. 2 When AP Released	Accelerator Position No. 1 When AP Depressed	Accelerator Position No. 2 When AP Depressed
VCP circuit open	0 to 0.2 V	0 to 0.2 V	0 to 0.2 V	0 to 0.2 V
Open or ground short in VPA circuit	0 to 0.2 V	1.2 to 2.0 V	0 to 0.2 V	3.4 to 5.0 V
Open or ground short in VPA2 circuit	0.5 to 1.1 V	0 to 0.2 V	2.6 to 4.5 V	0 to 0.2 V
EPA circuit open	4.5 to 5.0 V	4.5 to 5.0 V	4.5 to 5.0 V	4.5 to 5.0 V
Normal condition	0.5 to 1.1 V	1.2 to 2.0 V	2.6 to 4.5 V	3.4 to 5.0 V

HINT:

Accelerator pedal positions are expressed as voltages.
AP stands for Accelerator Pedal.

Monitor description

When either output voltage of VPA or VPA2 deviates from the standard range, or the difference between the output voltages of the 2 sensor circuits is less than the threshold, the ECM determines that there is a malfunction in the APP sensor. The ECM then illuminates the MIL and stores DTC(s). Example: When the output voltage of VPA drops below 0.4 V for more than 0.5 seconds when the accelerator pedal is fully depressed, DTC P2122 is stored. If the malfunction is not repaired successfully, a DTC is stored 2 seconds after the engine is next started.

FAIL-SAFE

When any of DTCs P2120, P2121, P2122, P2123, P2125, P2127, P2128 and P2138 is stored, the ECM enters fail-safe mode. If either of the 2 sensor circuits malfunctions, the ECM uses the remaining circuit to calculate the accelerator pedal position to allow the vehicle to continue driving. If both of the circuits malfunction, the ECM regards the accelerator pedal as being released. As a result, the throttle valve is closed and the engine idles. Fail-safe mode continues until a pass condition is detected, and the engine switch is turned off.

Wiring diagram

Inspection procedure

HINT:

These DTCs relate to the Accelerator Pedal Position (APP) sensor.
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition 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.

1.READ VALUE USING INTELLIGENT TESTER (ACCELERATOR POSITION SENSOR)

Diagnostic trouble code P2123 P2125 P2127 P2128 P2138 3UR-FE Land Cruiser Connect the intelligent tester to the DLC3.

Connect the intelligent tester to the DLC3.

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

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

Read the value displayed on the tester.

Standard Voltage:

Accelerator Pedal Operation	Accelerator Position No. 1	Accelerator Position No. 2
Released > Depressed > Released	0.5 to 4.5 V	1.2 to 5.0 V
Released > Depressed > Released	Difference between Accelerator Position No. 1 and Accelerator Position No. 2 is higher than 0.02 V	Difference between Accelerator Position No. 1 and Accelerator Position No. 2 is higher than 0.02 V

Result
Result	Proceed to
NG	A
OK	B

B

Go to step 5

A

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

Diagnostic trouble code P2123 P2125 P2127 P2128 P2138 3UR-FE Land Cruiser Disconnect the A31 accelerator pedal position (APP) sensor connector.

Disconnect the A31 accelerator pedal position (APP) sensor connector.

Disconnect the A38 ECM connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
A31-6 (VPA) - A38-55 (VPA)	Always	Below 1 ?
A31-5 (EPA) - A38-58 (EPA)	Always	Below 1 ?
A31-4 (VCPA) - A38-57 (VCPA)	Always	Below 1 ?
A31-3 (VPA2) - A38-56 (VPA2)	Always	Below 1 ?
A31-2 (EPA2) - A38-60 (EPA2)	Always	Below 1 ?
A31-1 (VCP2) - A38-59 (VCP2)	Always	Below 1 ?
A31-6 (VPA) or A38-55 (VPA) - body ground	Always	10 k? or higher
A31-5 (EPA) or A38-58 (EPA) - body ground	Always	10 k? or higher
A31-4 (VCPA) or A38-57 (VCPA) - body ground	Always	10 k? or higher
A31-3 (VPA2) or A38-56 (VPA2) - body ground	Always	10 k? or higher
A31-2 (EPA2) or A38-60 (EPA2) - body ground	Always	10 k? or higher
A31-1 (VCP2) or A38-59 (VCP2) - body ground	Always	10 k? or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.CHECK ECM (VCPA AND VCP2 VOLTAGE)

Diagnostic trouble code P2123 P2125 P2127 P2128 P2138 3UR-FE Land Cruiser Disconnect the A31 APP sensor connector.

Disconnect the A31 APP sensor connector.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
A31-4 (VCPA) - A31-5 (EPA)	Engine switch on (IG)	4.5 to 5.5 V
A31-1 (VCP2) - A31-2 (EPA2)	Engine switch on (IG)	4.5 to 5.5 V

NG

REPLACE ECM

OK

4.REPLACE ACCELERATOR PEDAL ASSEMBLY

Replace the accelerator pedal assembly .

NEXT

5.CHECK WHETHER DTC OUTPUT RECURS (ACCELERATOR PEDAL 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.

Enter the following menus: Powertrain / Engine and ECT / DTC.

Read DTCs.

Result
Result Proceed to
P2120, P2122, P2123, P2125, P2127, P2128, and/or P2138 are output A
No DTC is output B

B

SYSTEM OK

A

REPLACE ECM