Toyota Sequoia (2005). Manual - part 153

B17396

HT

+B

AF–

AF+

Sensor 1

A/F Sensor

Component Side:

Front View

A19288

–

DIAGNOSTICS

ENGINE

DI–407

601

HINT:
Read freeze frame data using a hand–held tester. Freeze frame data record the engine condition when mal-
functions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was mov-
ing 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 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:

Tester Connection

Specified Condition

HT (1) – +B (2)

Between 1.8 

Ω

 and 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

2

Check A/F relay.

PREPARATION:
Remove the A/F relay from the engine room J/B.
CHECK:
Inspect the A/F relay.
OK:

Terminal No.

Condition

Specified Condition

1 – 2

Constant

Continuity

Usually

No Continuity

3 – 5

Apply B+ between 

terminals 1 and 2

Continuity

NG

Replace EFI relay.

OK

A23659

Wire Harness Side:

HT

A38

Sensor 1

A/F Sensor Connector

AF+

Front View

AF–

+B

A39

B17415

A55007

E7

ECM Connector

HA1A

A1A+

A1A–

A2A+

A2A–

HA2A

A23512

Reference (Bank 1 Sensor 1 System Drawing):

A/F Sensor

A/F Relay

Heater

Sensor

A1A+

HA1A

Duty 
Control

ECM

From 
Battery

A/F Heater 
Fuse

A1A–

To EFI Relay

DI–408

–

DIAGNOSTICS

ENGINE

602

3

Check for open and short in harness and connector between ECM and A/F sen-
sor.

PREPARATION:
(a)

Disconnect the A38 or A39 A/F sensor connector.

(b)

Turn the ignition switch to ON.

CHECK:
(a)

Measure the voltage between the +B terminal of the A/F
sensor connector and body ground.

OK:

Standard:

Tester Connections

Specified Conditions

+B (2) – Body ground

Between 9 V and 14 V

PREPARATION:
(a)

Turn the ignition switch to OFF.

(b)

Disconnect the E7 ECM connector.

CHECK:
(a)

Check the resistance.

OK:

Standard (Check for open):

Tester Connections

Specified Conditions

HT (A38–1) – HA1A (E7–2)

HT (A39–1) – HA2A (E7–1)

Below 1 

Ω

AF+ (A38–3) – A1A+ (E7–22)

AF+ (A39–3) – A2A+ (E7–23)

Below 1 

Ω

AF– (A38–4) – A1A– (E7–30)

AF– (A39–4) – A2A– (E7–31)

Below 1 

Ω

Standard (Check for short):

Tester Connections

Specified Conditions

HT (A38–1) or HA1A (E7–2) – Body ground
HT (A39–1) or HA2A (E7–1) – Body ground

10 k

Ω

 or higher

AF+ (A38–3) or A1A+ (E7–22) – Body ground
AF+ (A39–3) or A2A+ (E7–23) – Body ground

10 k

Ω

 or higher

AF– (A38–4) or A1A– (E7–30) – Body ground
AF– (A39–4) or A2A– (E7–31) – Body ground

10 k

Ω

 or higher

–

DIAGNOSTICS

ENGINE

DI–409

603

NG

Replace or replace harness or connector.

OK

Replace ECM (See page 

SF–80

).

DI–410

–

DIAGNOSTICS

ENGINE

604

DTC

P2401

Evaporative Emission System Leak Detec-
tion Pump Control Circuit Low

DTC

P2402

Evaporative Emission System Leak Detec-
tion Pump Control Circuit High

DTC SUMMARY

DTCs

Monitoring Items

Malfunction Detection Conditions

Trouble Areas

Detection

Timings

Detection

Logic

P2401

Vacuum pump stuck OFF

Vacuum pump creates negative pressure
through 0.02 inch orifice, and EVAP system
pressure measured to determine leak pres-
sure standard. 0.02 inch leak pressure
standard is measured at the start and at the
end of the leak check.
If system pressure higher than –1.06 kPa
(–7.93 mmHg)*, or lower than –4.85 kPa
(–36.38 mmHg)*, ECM determines that
vacuum pump stuck OFF.

Pump module

Connector/Wire harness

(Pump module – ECM)

ECM

While 

ignition

switch

OFF

2 trip

P2402

Vacuum pump stuck ON

Vacuum pump creates negative pressure
through 0.02 inch orifice, and EVAP system
pressure measured to determine leak pres-
sure standard. 
If system pressure higher than –1.06 kPa
(–7.93 mmHg)*, or lower than –4.85 kPa
(–36.38 mmHg)*, ECM determines that
vacuum pump stuck ON.

Pump module

Connector/Wire harness

(Pump module – ECM)

ECM

While 

ignition

switch

OFF

2 trip

*: The threshold values vary according to the atmospheric pressure measured in operation A. The values
described in the table above are based on an atmospheric pressure of 100 kPa (750.1 mmHg).
HINT:
The vacuum pump is built into the pump module.

CIRCUIT DESCRIPTION

The circuit description can be found in the EVAP (Evaporative Emission) Inspection Procedure (see page

DI–460

).

DIDFV–01