Toyota Tundra. Manual — part 1175

MONITOR DESCRIPTION

Fig. 78: Coolant Temperature Threshold 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

DTC No.

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

Related DTCs

P0128: Coolant Thermostat

Required Sensors/Components
(Main)

Thermostat, Engine coolant temperature sensor

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

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

INSPECTION PROCEDURE

Monitor runs whenever following DTCs not present

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 -
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 - P0306 (Misfire)
P0335 (CKP sensor)
P0340 (VVT sensor)
P0351 - P0356 (Igniter)
P0500 (VSS)
P2196, P2198 (A/F sensor - rationality)
P2A00, P2A03 (A/F sensor - slow response)

Battery voltage

11 V or more

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 (1GR-FE) - Tundra

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.

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch ON.

c. Turn the Techstream ON.

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

e. Read DTCs.

Result

RESULT CHART

HINT:

If any DTCs other than P0128 are output, troubleshoot those DTCs first.

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

A : Go to next step

2. 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 : Go to next step

3. INSPECT WATER INLET WITH THERMOSTAT

a. Remove the water inlet with thermostat. (See REMOVAL ).

b. Measure the valve opening temperature of the thermostat.

Standard value:

Display (DTC Output) Proceed To

P0128

A

P0128 and other DTCs

B

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

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 water inlet with thermostat. (See INSTALLATION ).

NG : REPLACE WATER INLET WITH THERMOSTAT . (See THERMOSTAT ).

OK : REPLACE ECM . (See REMOVAL).

DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2); DTC P0137
OXYGEN SENSOR CIRCUIT LOW VOLTAGE (BANK 1 SENSOR 2); DTC P0138 OXYGEN
SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 2); DTC P0139 OXYGEN SENSOR
CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2); DTC P0156 OXYGEN SENSOR CIRCUIT
MALFUNCTION (BANK 2 SENSOR 2); DTC P0157 OXYGEN SENSOR CIRCUIT LOW VOLTAGE
(BANK 2 SENSOR 2); DTC P0158 OXYGEN SENSOR CIRCUIT HIGH VOLTAGE (BANK 2
SENSOR 2); DTC P0159 OXYGEN SENSOR CIRCUIT SLOW RESPONSE (BANK 2 SENSOR 2)

DESCRIPTION

HINT:

Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from
the engine assembly.

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 (Three-Way Catalytic Converter) 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 air-
fuel level. For the purpose of helping the ECM to deliver accurate air-fuel ratio control, a Heated Oxygen
(HO2) sensor is used.

The HO2 sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the
sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen
concentration even when the intake air volume is low (the exhaust gas temperature is low). When the air-fuel
ratio becomes lean, the oxygen concentration in the exhaust gas is rich. The HO2 sensor informs the ECM that
the post-TWC air-fuel ratio is lean (low voltage, i.e. less than 0.45 V). Conversely, when the air-fuel ratio is
richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas becomes lean. The
HO2 sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The
HO2 sensor has the property of changing its output voltage drastically when the air-fuel ratio is close to the
stoichiometric level.

The ECM uses the supplementary information from the HO2 sensor to determine whether the air-fuel ratio after
the TWC is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the HO2 sensor is working
improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air-fuel
ratio control.

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra