Toyota Sequoia (2005). Manual - part 238

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DIAGNOSTICS

AIR SUSPENSION SYSTEM

DI–747

941

DTC

C1741/41 Air Sus Relay Circuit

CIRCUIT DESCRIPTION

When the ”UP” side of the height control switch is pressed, a signal is sent from terminal RC of the suspen-
sion control ECU to the AIR SUS relay to turn it on.
As a result, the current flows to the AIR SUS relay coil, closing the relay contact, and then the battery positive
voltage is applied to the compressor, which causes the compressed air to raise the vehicle height.

DTC No.

DTC Detecting Condition

Trouble Area

C1741/41

Either of the following conditions is detected:
1. With the AIR SUS relay inactivated, an open signal of the

AIR SUS relay is detected for 1 sec. or more.

2. With the AIR SUS relay activated, a short signal of the AIR

SUS relay is detected 8 times successively.

AIR SUS relay

AIR SUS relay circuit

Suspension control ECU

HINT:
Once the ECU stores DTC C1741/41 in the memory, the vehicle height control is suspended until a normal
signal is input to the ECU from the AIR SUS relay. However, the control resumes if the ignition switch is turned
OFF, and then turned ON again.

DIDDT–01

F19443

Height Control
Compressor

H13

1

Engine Room R/B No. 2

G–Y

AIR SUS Relay

Battery

J28
J/C

W

BM2

1

IC4

8

IA1

21

W

W

W

2

2

2

2

3

2

5

1

W

9

B

5

W–B

J8
J/C

A

A

W–B

1K

12

1F

9

A

W–B

IE

Suspension
Control
ECU

IA1

25

G–Y

S25

5

RC

F10 
Fusible Link Block

ALT

Instrument 
Panel J/B

AIR SUS

DI–748

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DIAGNOSTICS

AIR SUSPENSION SYSTEM

942

WIRING DIAGRAM

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DIAGNOSTICS

AIR SUSPENSION SYSTEM

DI–749

943

INSPECTION PROCEDURE

HINT:

If DTC C1761/61 (ECU malfunction) and/or C1774/74 (power source circuit) is displayed, perform the
inspection necessary for DTC C1761/61 (See page 

DI–761

) and/or C1774/74 (See page 

DI–763

) first.

(If DTC C1761/61 and C1774/74 are output at the same time, perform the inspection necessary for
DTC C1774/74 first.)

Start the inspection from step 1 when using the hand–held tester, and start from step 2 when not using
the hand–held tester.

1

Perform active test by 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 ”MOTOR RELAY” in the ACTIVE TEST, and operate it with the hand–held tester.

AIR SUSPENSION:

Item

Vehicle Condition / Test Details

Diagnostic Note

MOTOR RELAY

Turn AIR SUS relay / ON or OFF

Operation sound of motor can be heard

CHECK:
Check the operating sound of the AIR SUS relay when operating it with the hand–held tester.
OK:

The operating sound of the AIR SUS relay can be heard.

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

Replace suspension control ECU 
(See page 

IN–35

).

A

F19458

DI–750

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DIAGNOSTICS

AIR SUSPENSION SYSTEM

944

2

Inspect AIR SUS relay.

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

Tester connection

Resistance

3 – 5

10 k

Ω

 or higher

3 – 5

Below 1 

Ω

 

(When battery voltage is applied to ter-

minals 1–2)

NG

Replace AIR SUS relay.

OK