Toyota Sequoia (2005). Manual - part 164

A23458

Air–fuel Ratio Sensor Output:

Active A/F Control

A/F Sensor Output

Fuel Injection Volume

ON

OFF

Normal

Malfunction

10 Seconds

–

DIAGNOSTICS

ENGINE

DI–451

645

DTC

P2A00

A/F Sensor Circuit Slow Response (Bank 1
Sensor 1)

DTC

P2A03

A/F Sensor Circuit Slow Response (Bank 2
Sensor 1)

CIRCUIT DESCRIPTION

Refer to DTC P2195 on page 

DI–383

.

DTC No.

DTC Detection Conditions

Trouble Areas

P2A00
P2A03

Calculated test value for A/F sensor response rate deteriora-

tion level is less than threshold.

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

A/F sensor (sensor 1)

ECM

MONITOR DESCRIPTION

After engine is warmed up, the ECM performs air–fuel ratio feedback control to regulate the air–fuel ratio
at stoichiometric ratio. In addition, this vehicle performs Active A/F Ratio Control for approximately 10 se-
conds after preconditions met in order to measure the A/F sensor response rate. During active air–fuel ratio
control, the ECM forcibly increases and decreases the injection volume for certain amount based on learned
stoichiomentric air –fuel ratio during usual air–fuel feedback control, and measures the A/F sensor response
rate. The ECM calculates the signal from the A/F sensor while value for A/F sensor response rate deteriora-
tion level.
If the test value for A/F sensor response rate deterioration level is less than threshold, ECM interprets this
as a malfunction, and sets the DTC.

DIDFY–01

Vehicle speed

(40 –120 km/h)

25 – 75mph)

(g)

(h)

Warm up

3 minutes

DI–452

–

DIAGNOSTICS

ENGINE

646

CONFIRMATION DRIVING PATTERN

(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch to ON.

(c)

Turn the hand–held tester ON.

(d)

Clear DTCs.

(e)

Select the following menu items: DIAGNOSIS/ENHANCED OBD II/MONITOR INFO/MONITOR RE-
SULT.

(f)

Check that RES RATE B1 S1 is INCOMPL.

(g)

Start the engine and warm it up.

(h)

Drive the vehicle at between 25 mph and 75 mph (40 km/h and 120km/h) for 3 minutes. However, the
vehicle should be driven at constant–speed.

(i)

When detection is complete, Response rate of MONITOR RESULT changes.

If the value does not change, perform step (g) once more.
(j)

Notes the value of the Monitor Result.

(k)

Select the following menu items: DIAGNOSIS/ENHANCED OBD II/DTC INFO/ PENDING CODES.

(l)

Check if any DTCs (any pending DTCs) are set.

MONITOR STRATEGY

R l t d DTC

P2A00

A/F sensor (Bank 1) slow response

Related DTCs

P2A03

A/F sensor (Bank 2) slow response

Required sensors/components

A/F sensor

Frequency of operation

Once per driving cycle

Duration

10 to 15 sec.

MIL operation

2 driving cycles

Sequence of operation

None

–

DIAGNOSTICS

ENGINE

DI–453

647

TYPICAL ENABLING CONDITIONS

It

Specification

Item

Minimum

Maximum

The monitor will run whenever these

DTCs are not present

See page 

DI–18

Battery voltage

11 V

–

ECT

75

°

C (167

°

F)

–

Idle

OFF

Engine RPM

–

4,000 rpm

A/F sensor status

Activated

Fuel cut

OFF

Engine load

10 to 70%

Estimated catalyst temperature

500 to 800

°

C (932 to 1,472

°

F)

Shift position

2nd

–

Catalyst monitor

Not executing

Intake air amount

2.5 to 12 g/sec

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria

Threshold

Response rate deterioration level

Less than 0.2 V

Number of average

5 or more

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 OBD ll scan tools.

A/F sensor bank 1 sensor 1

MID

TID

Scaling

Description of Test Value

Minimum Test Limit

Maximum Test Limit

$01

$8E

Multiply by 0.0003

(no dimension)

Response rate deterioration level for

A/F sensor

Malfunction criterion

FF

A/F sensor bank 2 sensor 1

MID

TID

Scaling

Description of Test Value

Minimum Test Limit

Maximum Test Limit

$05

$8E

Multiply by 0.0003

(no dimension)

Response rate deterioration level for

A/F sensor

Malfunction criterion

FF

WIRING DIAGRAM

Refer to DTC P2195 on page 

DI–383

.

DI–454

–

DIAGNOSTICS

ENGINE

648

INSPECTION PROCEDURE

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 (AFS B2S1) and OS2 B1S2
(O2S B2S2)) 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.
Standard:

Tester Display

(Sensor)

Injection Volumes

Status

Voltages

AFS B1S1 (AFS B2S1)

(A/F)

+25 %

Rich

Less than 3.0

AFS B1S1 (AFS B2S1)

(A/F)

–12.5 %

Lean

More than 3.35

O2S B1S2 (O2S B2S2)

(HO2)

+25 %

Rich

More than 0.55

O2S B1S2 (O2S B2S2)

(HO2)

–12.5 %

Lean

Less than 0.4