Toyota Sequoia (2005). Manual - part 114

A23541

At least 3 minutes

2 seconds

Check

2 seconds

Engine Speed

3,000 rpm

2,000 rpm

Idling

Ignition Switch OFF

(a)

(b)

(c)

(d)

Time

Warming up

(d)

–

DIAGNOSTICS

ENGINE

DI–251

445

MONITOR RESULT

Refer to page 

DI–26

 for detailed information.

The test value and test limit information are described as shown in the following table. Check the monitor
result and test values after performing the monitor drive pattern (refer to ”Confirmation Monitor”).



MID (Monitor Identification Data) is assigned to each emissions–related component.



TID (Test Identification Data) is assigned to each test value.



Scaling is used to calculate the test value indicated on generic tools.

Catalyst bank 1 – Active A/F control method

MID

TID

Scaling

Description of Test Value

Minimum Test Limit

Maximum Test Limit

$21

$A9

Multiply by 0.0003

(no dimension)

Oxygen storage capacity of catalyst

Minimum test limit for catalyst

Maximum test limit for catalyst

Catalyst bank 2 – Active A/F control method

MID

TID

Scaling

Description of Test Value

Minimum Test Limit

Maximum Test Limit

$22

$A9

Multiply by 0.0003

(no dimension)

Oxygen storage capacity of catalyst

Minimum test limit for catalyst

Maximum test limit for catalyst

WAVEFORMS OF AIR–FUEL RATIO (A/F) AND HEATED OXYGEN (HO2) SEN-
SORS

HINT:
Perform the operation with the engine speeds and time durations described below prior to check the wave-
forms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropri-
ate inspection results.

(a)

Connect the hand–held tester to the DLC3.

(b)

Start the engine and warm it up with all the accessories switched OFF, until the engine coolant temper-
ature stabilizes.

(c)

Run the engine at an engine speed of between 2,500 rpm and 3,000 rpm for at least 3 minutes.

(d)

After confirming that the waveform of the heated oxygen sensor (bank 1, 2 sensor 1 (HA1A, HA2A)),
oscillate around 0.5 V during feedback to the ECM, check the waveform of the heated oxygen sensor
(bank 1, 2 sensor 2 (OX1B, OX2B)).

A23542

Normal Catalyst

Deteriorated Catalyst

Waveform of 
A/F Sensor 
in front of TWC

Waveform of 
HO2 Sensor 
behind TWC

Voltage output when active air–fuel ratio control not performed

3.5 V

3.0 V

1.0 V

0 V

10 seconds

10 seconds

DI–252

–

DIAGNOSTICS

ENGINE

446

HINT:



If either of the voltage outputs of the Air–Fuel Ratio (A/F) or Heated Oxygen (HO2) sensors does not
fluctuate, or either of the sensors makes a noise, the sensor may be malfunctioning.



If the voltage outputs of both the sensors remain lean or rich, the air–fuel ratio may be extremely lean
or rich. In such cases, perform the following A/F CONTROL using a hand–held tester.



If the Three–Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the
TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active
air–fuel ratio control is not performed).

A/F CONTROL

HINT:
Hand–held tester only:
Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE
TEST. The A/F CONTROL function can help to determine whether the Air–Fuel Ratio (A/F) sensor, Heated
Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the A/F CONTROL operation using a hand–held tester.

(1)

Connect a hand–held tester to the DLC3.

(2)

Start the engine and turn the tester ON.

(3)

Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.

(4)

On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE
TEST / A/F CONTROL.

(5)

Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT
or LEFT button to change the fuel injection volume).

(6)

Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and OS2 B1S2) displayed
on the tester.

HINT:



The A/F CONTROL 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.

+25 %

–12.5 %

More than 3.35 V

Less than 3.0 V

1

A/F Sensor (Sensor 1) 
Output Voltage

Injection volume

Output voltage

HO2 Sensor (Sensor 2) 
Output Voltage

Main Suspected 
Trouble Areas

OK

+25 %

–12.5 %

More than 3.35 V

Less than 3.0V

Injection volume

Output voltage

+25 %

–12.5 %

More than 0.55 V

Less than 0.4V

Injection volume

Output voltage

A/F sensor

+25 %

–12.5 %

More than 0.55 V

Less than 0.4V

Injection volume

Output voltage

+25 %

–12.5 %

Injection volume

Output voltage

NG

+25 %

–12.5 %

Injection volume

Output voltage

NG

+25 %

–12.5 %

Injection volume

Output voltage

NG

+25 %

–12.5 %

Injection volume

Output voltage

NG

OK

OK

OK

Almost 

no reaction



Almost 

no reaction

Almost 

no reaction

Almost 

no reaction

Case

2

3

4

A/F sensor circuit

A/F sensor heater

HO2 sensor

HO2 sensor circuit

HO2 sensor heater

(Air–fuel ratio extremely 
lean or rich)

Injector

Gas leakage from 
exhaust system

Fuel pressure

–

DIAGNOSTICS

ENGINE

DI–253

447

Standard:

Tester Display

(Sensor)

Injection Volumes

Status

Voltages

AFS B1S1

(A/F)

+25 %

Rich

Less than 3.0

AFS B1S1

(A/F)

–12.5 %

Lean

More than 3.35

O2S B1S2

(HO2)

+25 %

Rich

More than 0.55

O2S B1S2

(HO2)

–12.5 %

Lean

Less than 0.4

NOTICE:
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.



Following the A/F CONTROL procedure enables technicians to check and graph the voltage outputs
of both the A/F and HO2 sensors.



To display the graph, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD
II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2, and press the YES but-
ton and then the ENTER button followed by the F4 button.

DI–254

–

DIAGNOSTICS

ENGINE

448

INSPECTION PROCEDURE

HINT:
Read freeze frame data using 

the hand−held tester

. Freeze frame data records the engine conditions when

a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was
running or stopped, if the engine was warmed up or not, if the air–fuel ratio was lean or rich, as well as other
data from the time when a malfunction occurred.

1

Are there any other codes (besides DTC P0420 or P0430) being output?

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch ON and push the hand–held tester main switch ON.

(c)

When using hand–held tester, enter the following menu: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / CURRENT CODES.

CHECK:
Read the DTC using the hand–held tester.
RESULT:

Display (DTC Output)

Proceed to

”P0420 and/or P0430”

A

”P0420 or P0430” and other DTCs

B

HINT:
If any other codes besides ”P0420 and/or P0430” are output, perform the troubleshooting for those DTCs
first.

B

Go to relevant DTC chart (See page 

DI–58

).

A

2

Check A/F sensor (bank 1, 2 sensor 1).

(a)

Connect the hand–held tester to the DLC3.

(b)

Start the engine and turn the tester ON.

(c)

Warm up the engine with the engine speed at 2,500 rpm for approximately 90 seconds.

(d)

On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST /
A/F CONTROL.

(e)

Perform the A/F CONTROL 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) displayed on the
tester.

HINT:



The A/F CONTROL 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.