Toyota Tundra. Manual — part 1546



A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would
cause the engine to run rich.



A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would
cause the engine to run lean.

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch to ON and turn the Techstream ON.

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

d. Read DTCs.

Result

RESULT REFERENCE

HINT:

If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.

B: GO TO DTC CHART

A: Go to Next Step

2. CHECK SENSOR OUTPUT

a. Warm up the engine until the engine coolant temperature is 75°C (167°F) or more.

b. Connect the Techstream to the DLC3.

c. Stop the engine.

d. Turn the ignition switch to ON.

e. Turn the Techstream on.

f. Write down the freeze frame data.

HINT:

By looking at the alcohol concentration learned value, Long FT and Short FT in the freeze frame
data, it is possible to determine the actual A/F deviation when a malfunction occurs.

g. Clear the DTCs (See DTC CHECK/CLEAR ).

HINT:

Even if no DTCs are stored, perform the DTC clear operation to start alcohol concentration

Result

Proceed to

P0171, P0172, P0174 or P0175 is output

A

P0171, P0172, P0174 or P0175 and other DTCs are output

B

2009 Toyota Tundra

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

learning.

h. Enter the following menus: Powertrain/Engine and ECT/Data List/Flexible Fuel Vehicle.

i. Immediately record data using snapshots.

j. Start the engine.

HINT:

After clearing the DTCs, the engine may become difficult to start if the concentration of alcohol in
the fuel is high.

Therefore, it may be necessary to crank the engine a few times before it starts.

k. Drive the vehicle at 32 km/h (20 mph) or more and maintain a constant speed for 2 minutes or

more.

HINT:



Make sure that the Data List "Alcohol Density Learning" is "Compl".



If the vehicle is not driven, a long time is required before "Alcohol Density Learning" is
"Compl".

l. Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2 or

AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

Result

RESULT REFERENCE

Result

Proceed to

A/F sensor output between 3.1 and 3.4 V
and
O2 sensor output slowly changes in the range of 0 and 1 V
and
Aggregate fuel trim*1 between -20 and 65%

C

A/F sensor output consistently outside range of 3.1 to 3.4 V
and
O2 sensor output and A/F sensor output contradict each other*2

B

A/F sensor and O2 sensor output both consistently indicate rich or lean
or
Aggregate fuel trim*1 less than -20%
or
Aggregate fuel trim*1 more than 65%

A

HINT:



*1: 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

2009 Toyota Tundra

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



Sensor Output Reference Values

SENSOR OUTPUT REFERENCE VALUES



Reference values when normal (E0 Fuel)

SENSOR OUTPUT REFERENCE VALUES - NORMAL (E0 FUEL)



Reference values when A/F sensor (Bank 1) is malfunctioning (E0 Fuel)

SENSOR OUTPUT REFERENCE VALUES - A/F SENSOR MALFUNCTIONING



*2: For example, the A/F sensor output indicates rich while the O2 sensor output indicates
lean.

Air-fuel Ratio A/F Sensor

HO2 Sensor

Lean

Higher than 3.25 V Below 0.4 V

Rich

Below 3.25 V

Higher than 0.55 V

AFS Voltage B1 S1

3.28 V

AFS Voltage B2 S1

3.28 V

O2S B1 S2

0.76 V

O2S B2 S2

0.70 V

Short FT #1

1%

Long FT #1

-6%

Short FT #2

2%

Long FT #2

-6%

AF Lambda B1 S1

0.99

AF Lambda B2 S1

0.99

Alcohol Density Estimate 0%
Alcohol Density Learning Compl

AFS Voltage B1 S1

4.99 V

AFS Voltage B2 S1

3.25 V

O2S B1 S2

0.95 V

O2S B2 S2

0.74 V

Short FT #1

0%

Long FT #1

17.1%

Short FT #2

0%

Long FT #2

-6.3%

AF Lambda B1 S1

1.23

AF Lambda B2 S1

0.99

Alcohol Density Estimate 41%
Alcohol Density Learning Compl

2009 Toyota Tundra

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



Reference values when purge hose disconnected (both banks are lean) (E0 Fuel)

SENSOR OUTPUT REFERENCE VALUES - PURGE HOSE DISCONNECTED



Reference values when air leak of the intake system during fuel system malfunction (actual
air-fuel ratio deviation) (E85 Fuel)

SENSOR OUTPUT REFERENCE VALUES - ACTUAL AIR-FUEL RATIO
DEVIATION

B: Go to step 12

C: Go to step 16

A: Go to Next Step

3. READ VALUE USING TECHSTREAM (MAF)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch to ON.

AFS Voltage B1 S1

3.45 V

AFS Voltage B2 S1

3.56 V

O2S B1 S2

0.03 V

O2S B2 S2

0.03 V

Short FT #1

20.3%

Long FT #1

-1.6%

Short FT #2

19.5%

Long FT #2

-6.3%

AF Lambda B1 S1

1.04

AF Lambda B2 S1

1.08

Alcohol Density Estimate 85%
Alcohol Density Learning Compl

AFS Voltage B1 S1

3.92 V

AFS Voltage B2 S1

3.94 V

O2S B1 S2

0.01V

O2S B2 S2

0.01V

Short FT #1

20.3%

Long FT #1

22.6%

Short FT #2

20.3%

Long FT #2

21.8%

AF Lambda B1 S1

1.20

AF Lambda B2 S1

1.20

Alcohol Density Estimate 85%
Alcohol Density Learning Compl

2009 Toyota Tundra

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