Toyota Sequoia (2005). Manual - part 92

–

DIAGNOSTICS

ENGINE

DI–171

365

3

Check air induction system (See page 

SF–1

).

CHECK:
Check the air induction system for vacuum leaks.

NG

Repair or replace air induction system.

OK

4

Perform active test (A/F control).

(a)

Connect the hand–held tester to the DLC3.

(b)

Start the engine and turn the tester ON.

(c)

Warm up the engine at an engine speed of 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 A/F and HO2 sensors(AFS B1S1 (AFS B2S1) and O2S 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

Result:

Status 

AFS B1S1

(AFS B2S1)

Status 

O2S B1S2

(O2S B2S2)

A/F Condition and 

A/F Sensor Condition

Misfires

Suspected Trouble Areas

Proceed To

Lean/Rich

Lean/Rich

Normal





C

Lean

Lean

Actual air–fuel ratio lean

May occur

PCV valve and hose

PCV hose connections

Injector blockage

Gas leakage from exhaust system

Air induction system

Fuel pressure

Mass Air Flow (MAF) meter

Engine Coolant Temperature (ECT)
sensor

A

DI–172

–

DIAGNOSTICS

ENGINE

366

Rich

Rich

Actual air–fuel ratio rich



Injector leakage or blockage

Gas leakage from exhaust system

Ignition system

Fuel pressure

MAF meter

ECT sensor

A

Lean

Lean/Rich

A/F sensor malfunction



A/F sensor

B

Rich

Lean/Rich

A/F sensor malfunction



A/F sensor

B

Lean: During A/F CONTROL, 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 A/F CONTROL, the AFS is consistently less than 3.0 V, and the O2S is consistently more than
0.55 V.

B

Go to step 11.

C

Go to step 15.

A

5

Read value of engine coolant temperature.

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch to ON and turn the tester ON.

(c)

Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / COOLANT
TEMP.

CHECK:
(a)

Read the COOLANT TEMP twice, when the engine is cold and also when warmed up.
Standard: 
With cold engine: Same as ambient air temperature.
With warm engine: Between 75



C and 95



C (167



F and 203



F)

NG

 Replace engine coolant temperature sensor.

OK

–

DIAGNOSTICS

ENGINE

DI–173

367

6

Read value of mass air flow meter.

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch to ON and turn the tester ON.

(c)

Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / MAF and
COOLANT TEMP.

(d)

Allow the engine to idle until the COOLANT TEMP reaches 75



C (167



F) or more.

CHECK:
(a)

Read the MAF with the engine in an idling condition and at an engine speed of 2,500 rpm.
Standard:
MAF while engine idling: Between 1.4 gm/s and 2.3 gm/s (shift position: N, A/C: OFF).
MAF at engine speed of 2,500 rpm: Between 5.4 gm/s and 7.9 gm/s (shift position: N, A/C: OFF).

NG

Replace mass air flow meter.

OK

7

Check fuel pressure (See page 

SF–7

).

CHECK:
Check the fuel pressure (high or low pressure).

NG

Check and replace fuel pump, pressure regula-
tor, fuel pipe line and filter (See page 

SF–1

).

OK

8

Check exhaust system for gas leakage.

OK:

No exhaust gas leakage.

NG

Repair or replace exhaust gas leakage point.

OK

B17396

HT

+B

AF–

AF+

Sensor 1

A/F Sensor

Component Side:

Front View

DI–174

–

DIAGNOSTICS

ENGINE

368

9

Check for spark and ignition (See page 

IG–1

).

HINT:
If the spark plugs or ignition system malfunction, engine misfire may occur. The misfire counter can be read
with the hand–held tester. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST / MIS-
FIRE / CYL#1 (to CYL#8).

NG

Repair or replace ignition system.

OK

10

Check injector injection (See page 

SF–29

).

HINT:
If the injectors malfunction, engine misfires may occur. The misfire counter can be read with the hand–held
tester. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST / MISFIRE / CYL#1 (to
CYL#8).

NG

Replace injector.

OK

11

Check resistance of air–fuel ratio (A/F) sensor heater.

PREPARATION:
Disconnect the air–fuel ratio (A/F) sensor connector.
CHECK:
Measure resistance between the terminals of the A/F sensor
connector.
OK:

Standard:

Tester Connection

Specified Condition

HT (1) – +B (2)

1.8 to 3.4 

Ω

 at 20



C (68



F)

HT (1) – AF– (4)

10 k

Ω

 or higher

NG

Replace air–fuel ratio (A/F) sensor.

OK