Toyota Tundra. Manual — part 1350

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 set 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)

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 (See DIAGNOSTIC TROUBLE CODE CHART )

A : Go To Next Step

Monitor runs whenever following DTCs not present

P0110 - P0113 (IAT sensor)
P0115 - P0118 (ECT sensor)

Thermostat failure

Not detected

Engine coolant temperature

Less than 0°C (32°F)

Result

Proceed To

P0125 is output

A

P0125 and other DTCs are output

B

2008 Toyota Tundra

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

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 INSTALLATION ).

NG : REPLACE THERMOSTAT . (See THERMOSTAT ).

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

OK : REPLACE ENGINE COOLANT TEMPERATURE SENSOR (See REMOVAL )

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

DESCRIPTION

This DTC is set 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

MONITOR DESCRIPTION

DTC Code

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

2008 Toyota Tundra

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

Fig. 80: Coolant Temperature Thermostat Regulating Graph

The ECM estimates the ECT based on the starting temperature, engine loads, and engine speeds. The ECM then
compares the estimated temperature with the actual ECT. When the estimated ECT reaches 75°C (167°F), the
ECM checks the actual ECT. If the actual ECT is less than 75°C (167°F), the ECM interprets this as a
malfunction in the thermostat or the engine cooling system and sets the DTC.

MONITOR STRATEGY

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

Related DTCs

P0128: Coolant Thermostat

Required Sensors/Components
(Main)

Thermostat

Required Sensors/Components
(Related)

Engine Coolant Temperature (ECT) sensor, Intake Air Temperature
(IAT) sensor, Vehicle speed sensor

Frequency of Operation

Once per driving cycle

Duration

900 seconds

MIL Operation

2 driving cycles

Sequence of Operation

None

P0010, P0020 (VVT OCV)
P0011 (VVT System 1 - Advance)
P0012 (VVT System 1 - Retard)
P0021 (VVT System 2 - Advance)
P0022 (VVT System 2 - Retard)
P0031, P0032, P0051, P0052 (A/F Sensor Heater

2008 Toyota Tundra

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

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

INSPECTION PROCEDURE

HINT:



This DTC relates to the thermostat.



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.

Monitor runs whenever following DTCs not present

- Sensor 1)
P0102 - P0103 (MAF meter)
P0110 - P0113 (IAT sensor)
P0115 - P0118 (ECT sensor)
P0125 (Insufficient ECT for Closed Loop)
P0171, P0172 (Fuel system)
P0300 - P0308 (Misfire)
P0335 (CKP sensor)
P0340 - P0346 (VVT sensor 1, 2)
P0351 - P0358 (Igniter)
P0500 (VSS)
P2196, P2198 (A/F sensor - rationality)
P2237, P2240 (A/F sensor - open)
P2A00, P2A03 (A/F sensor - slow response)

Battery voltage

11 V or higher

Either of following conditions 1 or 2 met:

-

1. All of following conditions met:

-



ECT at engine start - IAT at engine start

-15 to 7°C (-27 to 12.6°F)



ECT at engine start

-10 to 56°C (14 to 133°F)



IAT at engine start

-10 to 56°C (14 to 133°F)

2. All of following conditions met:

-



ECT at engine start - IAT at engine start

More than 7°C (12.6°F)



ECT at engine start

56°C (133°F) or less



IAT at engine start

-10°C (14°F) or more

Accumulated time at 128 km/h (80 mph) or more of
vehicle speed

Less than 20 seconds

Duration that both of following conditions (a) and (b) met

5 seconds or more

(a) Estimated ECT

75°C (167°F) or more

(b) ECT sensor output

Below 75°C (167°F)

2008 Toyota Tundra

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