Toyota Tundra. Manual — part 1544

A: Go to Next Step

25. INSPECT HEATED OXYGEN SENSOR

a. Disconnect the D31 or D32 HO2 sensor connector.

Fig. 104: Identifying Terminals Of D31 Or D32 HO2 Sensor Connectors
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

b. Measure the resistance according to the value(s) in the table below.

Standard resistance

RESISTANCE SPECIFIED CONDITION

NG: REPLACE HEATED OXYGEN SENSOR (See REMOVAL )

OK: Go to Next Step

26. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)

a. Turn the ignition switch off and wait for 5 minutes.

b. Disconnect the D74 ECM connector.

Tester Connection Condition Specified Condition

2 (+B) - 3 (OX1B)

Always

10 kohms or higher

2 (+B) - 4 (E1)

Always

10 kohms or higher

2 (+B) - 3 (OX2B)

Always

10 kohms or higher

2 (+B) - 4 (E1)

Always

10 kohms or higher

2009 Toyota Tundra

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

Fig. 105: Identifying Terminals Of D74 ECM Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

c. Measure the resistance according to the value(s) in the table below.

Standard resistance

RESISTANCE SPECIFIED CONDITION

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: REPLACE ECM (See REMOVAL )

27. PERFORM CONFIRMATION DRIVING PATTERN

HINT:

Refer to the CONFIRMATION DRIVING PATTERN

28. READ DTC OUTPUT (DTC P0139 OR P0159 IS OUTPUT AGAIN)

a. Read the DTCs.

Result

Tester Connection

Condition Specified Condition

D74-45 (HT1B) - D74-114 (OX1B) Always

10 kohms or higher

D74-44 (HT2B) - D74-112 (OX2B) Always

10 kohms or higher

2009 Toyota Tundra

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

RESULT REFERENCE

B: CHECK FOR INTERMITTENT PROBLEMS (See CHECK FOR INTERMITTENT
PROBLEMS )

A: REPLACE HEATED OXYGEN SENSOR (See REMOVAL )

DTC P0171 SYSTEM TOO LEAN (BANK 1); DTC P0172 SYSTEM TOO RICH (BANK 1); DTC P0174
SYSTEM TOO LEAN (BANK 2); DTC P0175 SYSTEM TOO RICH (BANK 2)

DESCRIPTION

This FFV can be used with unleaded gasoline or a combination of unleaded gasoline and E85.

E85 is a fuel with an ethanol concentration of 70 to 85% which meets the ASTM standards.

The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim
consists of both the short-term (Short FT) and long-term (Long FT) fuel trims, and the alcohol concentration
learned value (Alcohol Density Estimate).

The short-term fuel trim is fuel compensation that is used to constantly maintain the air-fuel ratio at
stoichiometric levels. The signal from the Air-Fuel Ratio (A/F) sensor indicates whether the air-fuel ratio is rich
or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air-fuel
ratio is rich and an increase in the fuel injection volume if it is lean.

Factors such as individual engine differences, wear over time and changes in operating environment cause
short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel
compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-
term fuel trim compensation.

The alcohol concentration learned value (Alcohol Density Estimate) is the estimated concentration of alcohol in
the fuel as calculated by the ECM. The fuel injection volume is increased by approximately half the amount of
the alcohol concentration learned value (refer to the table below for exact quantities).

However, in addition to the concentration of alcohol in the fuel, the actual A/F deviation due to malfunctions in
the engine system is factored into the alcohol concentration learned value.

The fuel injection compensation amount, which is used to determine if DTCs P0171 to P0175 are stored, can be
calculated by using the following formula.

Aggregate fuel trim is equal to the following: Short FT + ((1 + Long FT/100) x (Injection Compensation
Amount) - 1) x 100

INJECTION COMPENSATION AMOUNT REFERENCE

Result

Proceed to

P0139 or P0159 is output

A

No DTC is output

B

2009 Toyota Tundra

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

Approximation:

Aggregate fuel trim is approximately equal to the following: Short FT + ((1 + Long FT/100) x (1 + (Alcohol
Density Estimate/2/100)) -1) x 100

As an example, when the Alcohol Density Estimate is exact, the following formulas are used.

When E85 fuel is used: Aggregate fuel trim = Short FT + ((1 + Long FT/100) x (1.383) -1) x 100

DTC DETECTION CONDITION AND TROUBLE AREA REFERENCE CHART

Alcohol Density Estimate

0% 10%

20% 30%

40%

50%

60%

70%

80%

85%

Injection Compensation Amount

1.0 1.051 1.10 1.148 1.194 1.238 1.282 1.323 1.364 1.383

DTC

DTC Detection Condition

Trouble Area

P0171
P0174

With warm engine and stable air-
fuel ratio feedback, fuel trim
considerably in error to lean side
(2 trip detection logic)



Air induction system



Injector blockage



Mass Air Row (MAF) meter



Engine Coolant Temperature
(ECT) sensor



Fuel pressure



Gas leak from exhaust
system



Open or short in A/F sensor
(for Sensor 1) circuit



A/F sensor (for Sensor 1)



A/F sensor heater (for Sensor
1)



Integration relay



A/F sensor heater and
integration relay circuits



PCV valve and hose



PCV hose connections



ECM



Fuel pressure switching valve



Fuel pressure regulator



Fuel pressure regulator for
high pressure



Fuel pump



Fuel pump ECU



Injector leak or blockage



MAF meter

2009 Toyota Tundra

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