Toyota Tundra. Manual — part 1416

DTC P2121 THROTTLE/PEDAL POSITION SENSOR/SWITCH "D" CIRCUIT
RANGE/PERFORMANCE

DESCRIPTION

HINT:

Refer to DTC P2120 .

DTC DETECTION CONDITION AND TROUBLE AREA

MONITOR DESCRIPTION

When the difference between the output voltages of VPA and VPA2 deviates from the standard, the ECM
determines that the Accelerator Pedal Position (APP) sensor is malfunctioning. The ECM turns on the MIL and
the DTC is set.

MONITOR STRATEGY

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

DTC

Code

DTC Detection Condition

Trouble Area

P2121

Difference between VPA and VPA2 less than 0.4 V, or higher
than 1.2 V for 0.5 seconds (1 trip detection logic)



Accelerator Pedal
Position (APP) sensor



ECM

Related DTCs

P2121: APP sensor rationality

Required Sensors/Components (Main)

APP sensor

Required Sensors/Components (Related)

-

Frequency of Operation

Continuous

Duration

0.5 seconds

MIL Operation

Immediate

Sequence of Operation

None

Monitor runs whenever following DTCs not present

None

Either of following conditions 1 or 2 met:

-

1. Ignition switch

ON

2. Throttle actuator power

ON

Difference between VPA voltage (learned value) and VPA2 voltage

Less than 0.4 V, or higher than

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

FAIL-SAFE

The APP sensor has two (main and sub) sensor circuits. If a malfunction occurs in either of the sensor circuits,
the ECM detects the abnormal signal voltage difference between the two sensor circuits and switches to limp
mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal opening angle to allow the
vehicle to continue driving. If both circuits malfunction, the ECM regards the opening angle of the accelerator
pedal as being fully closed. In this case, the throttle valve remains closed as if the engine is idling.

If a pass condition is detected and then the ignition switch is turned off, the fail-safe operation stops and the
system returns to a normal condition.

WIRING DIAGRAM

Refer to DTC P2120 .

INSPECTION PROCEDURE

HINT:



This DTC relates to the Accelerator Pedal Position (APP) sensor.



Read freeze frame data using the Techstream. 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. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2121)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch to ON.

c. Turn the Techstream ON.

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

e. Read DTCs.

Result

RESULT REFERENCE

HINT:

If any DTCs other than P2121 are output, troubleshoot those DTCs first.

(learned value)

1.2 V

Result

Proceed To

P2121 is output

A

P2121 and other DTCs are output

B

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

B : GO TO DTC CHART (See DIAGNOSTIC TROUBLE CODE CHART )

A : Go to Next Step

2. READ VALUE USING TECHSTREAM (ACCELERATOR POSITION SENSOR)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch to ON and turn the Techstream ON.

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

1 and Accelerator Position No. 2.

d. Read the values displayed on the Techstream.

Standard voltage

STANDARD VOLTAGE SPECIFICATION

Fig. 216: Identifying Accelerator Pedal Depressed & Released Position

NG : Go to step 3

OK : CHECK FOR INTERMITTENT PROBLEMS (See CHECK FOR INTERMITTENT
PROBLEMS )

3. REPLACE ACCELERATOR PEDAL

a. Replace the accelerator pedal assembly. (See REMOVAL ).

4. CHECK WHETHER DTC OUTPUT RECURS (DTC P2121)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch to ON and turn the Techstream ON.

c. Clear DTCs. (See DTC CHECK/CLEAR ).

d. Start the engine.

e. Allow the engine to idle for 15 seconds.

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

g. Read DTCs.

Accelerator Pedal Operations Accelerator Position No. 1 Accelerator Position No. 2

Released

0.5 to 1.1 V

1.2 to 2.0 V

Depressed

2.6 to 4.5 V

3.4 to 4.7 V

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

Result

RESULT REFERENCE

B : SYSTEM OK

A : REPLACE ECM (See REMOVAL )

DTC P2195 OXYGEN (A/F) SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1); DTC P2196
OXYGEN (A/F) SENSOR SIGNAL STUCK RICH (BANK 1 SENSOR 1); DTC P2197 OXYGEN (A/F)
SENSOR SIGNAL STUCK LEAN (BANK 2 SENSOR 1); DTC P2198 OXYGEN (A/F) SENSOR
SIGNAL STUCK RICH (BANK 2 SENSOR 1)

DESCRIPTION

The A/F sensor generates a voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to
provide the ECM with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from
the stoichiometric air-fuel ratio level, and regulates the fuel injection time. If the A/F sensor malfunctions, the
ECM is unable to control the air-fuel ratio accurately.

The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia
element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature
is low), a current flows into the heater to heat the sensor in order to facilitate accurate air-fuel ratio detection. In
addition, the sensor and heater portions are the narrow type. The heat generated by the heater is conducted to
the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide
(NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air-fuel ratio
must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is converted into
a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant
voltage.

Result

Proceed To

P2121 is output

A

No DTC is output

B

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra