Toyota Tundra. Manual — part 1349

Fig. 79: Identifying D9 Throttle Body Connector

NG : REPLACE ECM (See REMOVAL )

OK : Go To Next Step

4. REPLACE THROTTLE BODY ASSEMBLY

a. Replace the throttle body assembly. (See REMOVAL ).

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

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 or more.

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

g. Read DTCs.

Result

RESULT REFERENCE

B : SYSTEM OK

A : REPLACE ECM (See REMOVAL )

DTC P0121 THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUIT
RANGE/PERFORMANCE PROBLEM

DESCRIPTION

Refer to DTC P0120 .

Result

Proceed To

P0120, P0122, P0123, P0220, P0222, P0223 and/or P2135 are output

A

No DTC is output

B

2008 Toyota Tundra

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

DTC DETECTION CONDITION AND TROUBLE AREA

MONITOR DESCRIPTION

The ECM uses the TP sensor to monitor the throttle valve opening angle.

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 TP 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 of the TP sensor. The ECM illuminates the MIL and sets the DTC.

If the malfunction is not repaired successfully, the DTC is set 2 seconds after the engine is next started.

MONITOR STRATEGY

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

DTC

Code

DTC Detection Condition

Trouble Area

P0121

Difference between VTA1 and VTA2 voltages less than 0.8 V, or
higher than 1.6 V for 2 seconds
(1 trip detection logic)

TP sensor (built into
throttle body)

Related DTCs

P0121: TP sensor rationality

Required Sensors/Components (Main)

TP sensor

Required Sensors/Components (Related)

-

Frequency of Operation

Continuous

Duration

Within 2 seconds

MIL Operation

Immediate

Sequence of Operation

None

Monitor runs whenever following DTCs not present

None

Either of following conditions A or B set

-

A. Ignition switch

ON

B. Electric throttle motor power

ON

Difference in voltage between VTA1 and VTA2
TP sensor 1 - [TP sensor 2 x 0.8 (corrected by learning value)]

Less than 0.8 V, or higher than 1.6 V

2008 Toyota Tundra

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

FAIL-SAFE

When this DTC, as well as other DTCs relating to ETCS (Electronic Throttle Control System) malfunctions, is
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 7° 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.

Fail-safe mode continues until a pass condition is detected, and the ignition switch is then turned OFF.

INSPECTION PROCEDURE

HINT:



This DTC relates to the Throttle Position (TP) 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 P0121)

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

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

A : REPLACE THROTTLE BODY ASSEMBLY (See REMOVAL )

DTC P0125 INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP FUEL CONTROL

DESCRIPTION

Refer to DTC P0115 .

DTC DETECTION CONDITION AND TROUBLE AREA

Result

Proceed To

P0121 is output

A

P0121 and other DTCs are output

B

2008 Toyota Tundra

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

MONITOR DESCRIPTION

The resistance of the ECT sensor varies in proportion to the actual ECT. The ECT supplies a constant voltage to
the sensor and monitors the signal output voltage of the sensor. The signal output voltage varies according to
the changing resistance of the sensor. After the engine is started, the ECT is monitored through this signal. If the
ECT sensor indicates that the engine is not yet warm enough for closed-loop fuel control, despite a specified
period of time having elapsed since the engine was started, the ECM interprets this as a malfunction in the
sensor or cooling system and sets the DTC.

Example:

The ECT is 0°C (32°F) at engine start. After about 1 minute running time, the ECT sensor still indicates that the
engine is not warm enough to begin closed-loop fuel (air-fuel ratio feedback) control. The ECM interprets this
as a malfunction in the sensor or cooling system and sets the DTC.

MONITOR STRATEGY

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

DTC

Code

DTC Detection Condition

Trouble Area

P0125

Engine Coolant Temperature (ECT) does not reach closed-loop enabling
temperature for 20 minutes (this period varies with engine start ECT)
(2 trip detection logic)



ECT sensor



Cooling
system



Thermostat

Related DTCs

P0125: Insufficient engine coolant temperature for closed-loop fuel
control

Required Sensors/Components
(Main)

Thermostat, cooling system

Required Sensors/Components
(Related)

Engine coolant temperature sensor and mass air flow meter

Frequency of Operation

Once per driving cycle

Duration

77.63 seconds or more: Engine coolant temperature at engine start -
8.34°C (17°F) or more
129.03 seconds or more: Engine coolant temperature at engine start -
19.45° to -8.34°C (-3° to 17°F)
20 minutes or more: Engine coolant temperature at engine start less
than -19.45°C (-3°F)

MIL Operation

2 driving cycles

Sequence of Operation

None

P0102 - P0103 (MAF meter)

2008 Toyota Tundra

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