Toyota Tundra. Manual — part 1535

e. Read DTCs.

Result

RESULT REFERENCE

B: GO TO DTC 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 REFERENCE CHART

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

Result

Proceed to

P0121 is output

A

P0121 and other DTCs are output

B

DTC

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

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

WIRING DIAGRAM

Refer to DTC P0115 .

INSPECTION PROCEDURE

HINT:



If any of DTCs P0115, P0116, P0117 or P0118 are stored simultaneously with DTC P0125, the Engine
Coolant Temperature (ECT) sensor may have an open or a short circuit. Troubleshoot those DTCs first.



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 P0125)

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

62 seconds: Engine coolant temperature at engine start -8.33°C (17°
F) or more
107 seconds: Engine coolant temperature at engine start -19.44 to -
8.33°C (-3 to 17°F)
20 minutes: Less than engine coolant temperature at engine start -
19.44°C (-3°F)

MIL Operation

2 driving cycles

Sequence of Operation

None

Monitor runs whenever following DTCs not
present

P0128 (Thermostat)
P0112, P0113 (Intake Air Temperature Sensor)
P0115, P0117, P0118 (Engine Coolant Temperature
Sensor)
P0101, P0102, P0103 (Mass Air Flow Sensor)

Engine coolant temperature

Less than 0°C (32°F)

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra

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 P0125 are output, troubleshoot those DTCs first.

B: GO TO DTC CHART

A: Go to next step.

2. INSPECT THERMOSTAT

a. Remove the thermostat (see REMOVAL ).

b. Check the valve opening temperature of the thermostat.

Standard opening temperature: 80 to 84°C (176 to 183°F)

HINT:

In addition to the above check, confirm that the valve is completely closed when the temperature is
below the standard.

c. Reinstall the thermostat (see INSPECTION ).

NG: REPLACE THERMOSTAT (See REMOVAL )

OK: Go to next step.

3. CHECK COOLING SYSTEM

a. Check for defects in the cooling system that might cause the system to be too cold, such as

abnormal radiator fan operation or any modifications.

NG: REPAIR OR REPLACE COOLING SYSTEM

Result

Proceed to

P0125 is output

A

P0125 and other DTCs are output

B

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra

OK: REPLACE ENGINE COOLANT TEMPERATURE SENSOR (See REMOVAL )

DTC P0128 COOLANT THERMOSTAT (COOLANT TEMPERATURE BELOW THERMOSTAT
REGULATING TEMPERATURE)

DESCRIPTION

This DTC is stored when the Engine Coolant Temperature (ECT) does not reach 75°C (167°F) despite
sufficient engine warm-up time having elapsed.

DTC DETECTION CONDITION AND TROUBLE AREA REFERENCE CHART

MONITOR DESCRIPTION

Fig. 89: Coolant Thermostat Temperature Graph

DTC

DTC Detection Condition

Trouble Area

P0128

Conditions (a), (b) and (c) met for
5 seconds (2 trip detection logic):

a. Cold start

b. Engine warmed up

c. ECT less than 75°C (167°F)



Thermostat



Cooling system



ECT sensor



ECM

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra