Toyota Sequoia (2005). Manual - part 242

F19445

Engine Room R/B No. 2

F10
Fusible Link Block

Suspension Control
ECU

AIR SUS No. 2

2

1

2

2

W

AIR SUS

9

ALT

5

B

Battery

IF

J12
J/C

A

W–B

22

S25 GND

24

S25

25

S25 BAT

B

J/C

B

J37

B

J37

C

J38

V

IA5

5

V

V

V

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

DI–763

957

DTC

C1774/74 Power Source Circuit

CIRCUIT DESCRIPTION

This circuit provides power to operate the suspension control ECU.

The suspension control ECU, controlling the air suspension system, is activated when the ignition
switch is turned ON. The main relay inside the ECU is activated after 2 seconds and the system is oper-
ated by +B power source.

DTC No.

DTC Detecting Condition

Trouble Area

C1774/74

The terminal B or BAT voltage is below 10 V or above 16 V for
0.5 seconds.

Battery

Power source circuit

Suspension control ECU

WIRING DIAGRAM

DIDE3–01

DI–764

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

958

INSPECTION PROCEDURE

1

Inspect battery voltage.

CHECK:
Check the battery voltage.
OK:

Voltage: 11 to 14 V

NG

Replace battery.

OK

HINT:
Start the inspection from step 2 when using the hand–held tester, and start from step 3 when not using the
hand–held tester.

2

Read value of the hand–held tester.

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)

Select the item ”POWER VOLTAGE” in the DATA LIST, and read its value displayed on the hand–held
tester.

AIR SUSPENSION:

Item

Measurement Item / Range (Dis-

play)

Normal Condition

Diagnostic Note

POWER VOLTAGE

+B power source voltage / min.: 0

V, max.: 25.5 V

Actual battery power supply volt-

age: 10 to 14 V

–

CHECK:
Check the battery positive voltage.
OK:

Actual battery power supply voltage: 10 to 14 V

RESULT:

NG

A

OK (When troubleshooting according to the PROBLEM SYMPTOMS TABLE)

B

OK (When troubleshooting according to the DTC chart)

C

B

Proceed to next circuit inspection shown in
problem symptoms table (See page 

DI–716

).

C

Check for intermittent problems.

HINT:
Check the connector and terminal (See page 

IN–24

).

F16805

S25

BAT

B

Wire Harness View:

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

DI–765

959

A

3

Inspect fuse (AIR SUS No. 2).

PREPARATION:
Remove the AIR SUS No. 2 fuse from the engine room R/B.
CHECK:
Check continuity of the AIR SUS No. 2 fuse.
OK:

Continuity

NG

Inspect for short circuit in all harness and com-
ponents connected to AIR SUS No. 2 fuse.

OK

4

Inspect suspension control ECU.

PREPARATION:
Disconnect the ECU connector.
CHECK:
Measure the voltage between terminal S25–24 (B) of the sus-
pension control ECU connector and body ground and between
terminal S25–25 (BAT) and body ground.
OK:

Voltage: 10 to 14 V

NG

Repair or replace harness or connector.

OK

F16805

Wire Harness View:

GND

S25

DI–766

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

960

5

Check harness and connector (Suspension control ECU – Body ground).

CHECK:
Check continuity between terminal S25–22 (GND) and body
ground.
OK:

Continuity

NG

Repair or replace harness or connector.

OK

Replace suspension control ECU
(See page 

IN–35

).