Toyota Tundra. Manual — part 1536

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

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

Monitor runs whenever following
DTCs not present

P0010, P0020 (VVT Oil Control Valve)
P0011, P0021 (VVT System - Advance)
P0012, P0022 (VVT System - Retard)
P0016, P0018 (VVT System - Misalignment)
P0013, P0023 (Exhaust VVT Oil Control Valve)
P0014, P0024 (Exhaust VVT System - Advance)
P0015, P0025 (Exhaust VVT System - Retard)
P0017, P0019 (Exhaust VVT System - Misalignment)
P0031, P0032, P0051, P0052 (Air Fuel Ratio Sensor Heater)
P2195, P2196, P2197, P2198, P2237, P2238, P2239, P2240, P2241,
P2242, P2252, P2253, P2255, P2256, P2A00, P2A03 (Air Fuel Ratio
Sensor)
P0102, P0103 (Mass Air Flow Sensor)
P0112, P0113 (Intake Air Temperature Sensor)
P0115, P0117, P0118 (Engine Coolant Temperature Sensor)
P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle
Position Sensor)
P0171, P0172, P0174, P0175 (Fuel System)
P0301 - P0308 (Misfire)
P0335 (Crankshaft Position Sensor)
P1340 (Camshaft Position Sensor)
P0340, P0342, P0343, P0345, P0347, P0348 (VVT Sensor)
P0365, P0367, P0368, P0390, P0392, P0393 (Exhaust VVT Sensor)
P0351 - P0358 (Igniter)

2009 Toyota Tundra

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

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

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

P0500 (Vehicle Speed Sensor)

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)

2009 Toyota Tundra

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

RESULT REFERENCE

HINT:

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

B: GO TO DTC 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 THERMOSTAT

a. Remove the thermostat (see REMOVAL ).

b. Measure 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: 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)

Result

Proceed to

P0128 is output

A

P0128 and other DTCs are output

B

2009 Toyota Tundra

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

DESCRIPTION

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 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.

Fig. 90: Air Fuel Ratio Graph
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

DTC DETECTION CONDITION AND TROUBLE AREA REFERENCE CHART

DTC

DTC Detection Condition

Trouble Area



Abnormal voltage output:

During active air-fuel ratio
control, following conditions
(a) and (b) met for certain
period of time (2 trip
detection logic):

a. Heated Oxygen (HO2)

sensor voltage does not



Open or short in HO2 sensor
(for Bank 1, 2) circuit



HO2 sensor (for Bank 1, 2)

2009 Toyota Tundra

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