Toyota Tundra. Manual - part 1207

6. Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and

O2S B2 S2) displayed on the Techstream.

HINT:



The Control the Injection Volume for A/F sensor operation lowers the fuel injection volume by 12.5% or
increases the injection volume by 25%.



Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

VOLTAGE REFERENCE



Following the Control the Injection Volume for A/F sensor procedure enables technicians to check and
graph the voltage outputs of both the A/F and HO2 sensors.



To display the graph, enter the following menus: Powertrain/Engine and ECT/Active Test/Control the

Tester Display (Sensor)

Injection Volume Status

Voltage

AFS B1 S1 or AFS B2 S1 (A/F)

+25%

Rich

Less than 3.0 V

AFS B1 S1 or AFS B2 S1 (A/F)

-12.5%

Lean More than 3.35 V

O2S B1 S2 or O2S B2 S2 (HO2)

+25%

Rich More than 0.55 V

O2S B1 S2 or O2S B2 S2 (HO2)

-12.5%

Lean

Less than 0.4 V

NOTE:

The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the
Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20
seconds.

Case

A/F Sensor (Sensor 1) Output

Voltage

HO2 Sensor (Sensor 2)

Output Voltage

Main Suspected Trouble Area



A/F sensor



A/F sensor heater



A/F sensor circuit



HO2 sensor



HO2 sensor heater



HO2 sensor circuit



Injector



Fuel pressure



Gas leakage from exhaust
system (Air-fuel ratio
extremely rich or lean)

2008 Toyota Tundra

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

Injection Volume for A/F Sensor/A/F Control System/AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S
B2 S2.

HINT:

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 P0420 AND/OR P0430)

a. Connect the Techstream to the DLC3.

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

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

d. Read DTCs.

Result

RESULT CHART

HINT:

If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.

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

A : Go to next step

2. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME

FOR A/F SENSOR)

a. Connect the Techstream to the DLC3.

b. Start the engine and turn the Techstream ON.

c. Warm up the engine at an engine speed of 2500 RPM for approximately 90 seconds.

d. Enter the following menus: Powertrain/Engine and ECT/Active Test/Control the Injection Volume

for A/F sensor.

e. Perform the Active Test operation with the engine in an idling condition (press the RIGHT or

LEFT button to change the fuel injection volume).

f. Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1

and O2S B2S2) displayed on the Techstream.

HINT:

Display (DTC Output)

Proceed To

P0420 and/or P0430

P0420 and/or P0430 and other DTCs

2008 Toyota Tundra

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



The Control the Injection Volume for A/F sensor operation lowers the fuel injection volume
by 12.5% or increases the injection volume by 25%.



Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

Standard

VOLTAGE REFERENCE

Result

RESULT CHART

Tester Display (Sensor)

Injection Volume Status

Voltage

AFS B1S1 or AFS B2S1 (A/F)

+25%

Rich

Less than 3.0

AFS B1S1 or AFS B2S1 (A/F)

-12.5%

Lean More than 3.35

O2S B1S2 or O2S B2S2 (HO2)

+25%

Rich More than 0.55

O2S B1S2 or O2S B2S2 (HO2)

-12.5%

Lean

Less than 0.4

Status AFS

B1S1 or AFS

B2S1

Status O2S

B1S2 or O2S

B2S2

A/F Condition and

A/F and HO2

Sensors Condition

Misfire

Main Suspected

Trouble Area

Proceed

Lean/Rich

Normal



Three-Way
Catalytic
Converter (TWC)



Gas leakage from
exhaust system

Lean

Lean/Rich

A/F sensor
malfunction



A/F sensor

Rich

Lean/Rich

A/F sensor
malfunction



A/F sensor

Lean/Rich

Lean

HO2 sensor
malfunction



HO2 sensor



Gas leakage from
exhaust system

Lean/Rich

Rich

HO2 sensor
malfunction



HO2 sensor



Gas leakage from
exhaust system

Lean

Actual air-fuel ratio
lean

May

occur



Extremely rich or
lean actual air-
fuel ratio



Gas leakage from
exhaust system

Rich

Actual air-fuel ratio
rich



Extremely rich or
lean actual air-
fuel ratio

2008 Toyota Tundra

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

Lean: During Control the Injection Volume for A/F sensor, the A/F sensor output voltage (AFS) is
consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than
0.4 V. Rich: During Control the Injection Volume for A/F sensor, the AFS is consistently less than
3.0 V, and the O2S is consistently more than 0.55 V.

Lean/Rich: During Control the Injection Volume for A/F sensor of the Active Test, the output
voltage of the HO2 sensor alternates correctly.

B : REPLACE AIR FUEL RATIO SENSOR

C : Go to step 4

D : CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR-FUEL RATIO,
REPLACE FAULTY AREA AND GO TO NEXT STEP

A : Go to next step

3. INSPECT FOR EXHAUST GAS LEAK

OK: No gas leakage.

Result

RESULT CHART

B : Go to step 5

A : REPAIR OR REPLACE EXHAUST GAS LEAK POINT

4. INSPECT EXHAUST GAS LEAK

OK: No gas leakage.

NG : REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

OK : REPLACE HEATED OXYGEN SENSOR

5. CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)

a. According to the output DTCs in the step 1 (Check Any Other DTCs Output), proceed to next step

referring to the table below.



Gas leakage from
exhaust system

Result Proceed To

2008 Toyota Tundra

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

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