Toyota Sequoia (2005). Manual - part 236

F16805

Suspension Control ECU 
Wire Harness View:

S25

SLRL

F19436

Height Control Valve 
Wire Harness View:

H16

3 2 1

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

DI–739

933

3

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

PREPARATION:
Disconnect the ECU connector.
CHECK:
Check for an open or short circuit in the harness and the con-
nectors between terminal 1 of the height control valve and ter-
minal S25–4 (SLRL) of the suspension control ECU.
OK:

There is no open or short in the wire harness.

CHECK:
Check for an open circuit in the harness and the connectors be-
tween terminal 2 of the height control valve and body ground.
OK:

There is no open in the wire harness.

NG

Repair or replace harness or connector.

OK

Replace suspension control ECU
(See page 

IN–35

).

F19454

Suspension Control ECU

H16 
Leveling Solenoid Valve
(Height Control Valve)

LG–R

4

BM1

SLRR

3

13
IN1

3

S25

BI

W–B

2

LG–R

LG–R

DI–740

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

934

DTC

C1734/34 Leveling Solenoid Valve Circuit

CIRCUIT DESCRIPTION

The suspension control ECU opens the leveling solenoid valve (height control valve) to lead the compressed
air to the height control cylinder (pneumatic cylinder) and to raise the vehicle height.
The height control valve consists of a leveling solenoid valve and a gate solenoid valve.
The leveling solenoid valve opens and closes the passage between the compressor and the height control
cylinder (pneumatic cylinder).

DTC No.

DTC Detecting Condition

Trouble Area

C1734/34

Either of the following conditions is detected:
1. With the height control valve inactivated, an open signal of

the height control valve is detected for 1 sec. or more.

2. With the height control valve activated, a short signal of the

valve is detected 8 times successively.

Leveling solenoid valve (Height control valve)

Leveling solenoid valve (Height control valve) circuit

Suspension control ECU

HINT:

Once the ECU stores DTC C1734/34 in the memory, the vehicle height control is suspended until a
normal signal is input to the ECU from the height control solenoid valves. However, control is resumed
if the ignition switch is turned OFF, then ON again.

Malfunction in the leveling solenoid valve:
The height control operation is suspended, and the height control indicator lamp does not change by
operating the height control switch.

WIRING DIAGRAM

DIDDR–01

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

DI–741

935

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 the 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 using 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 ”LEVEL SOL REAR” in the ACTIVE TEST, and operate it with the hand–held tester.

AIR SUSPENSION:

Item

Vehicle Condition / Test Details

Diagnostic Note

LEVEL SOL REAR

Turn leveling solenoid valve / ON or OFF

Operation sound of solenoid (clicking sound) can

be heard

CHECK:
(a)

Check whether the solenoid makes sound.

(b)

Check whether the height control solenoid valve has continuity (will vibrate).

OK:

The solenoid makes sound, and the height control solenoid valve has continuity (will vibrate).

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

F19437

Connector Front View:

3 2 1

DI–742

–

DIAGNOSTICS

AIR SUSPENSION SYSTEM

936

2

Inspect leveling solenoid valve (height control valve).

PREPARATION:
Disconnect the valve connector.
CHECK:
Measure the resistance between terminals.
OK:

Solenoid valve

Tester connection

Resistance

Leveling solenoid valve

2 – 3

10 to 14 

Ω

CHECK:
Check the operating sound of the valves when battery voltage
is applied to the terminals as shown below.

Solenoid valve

Battery positive

Battery negative

Leveling solenoid valve

3

2

OK:

Operating sound (clicking) can be heard.

HINT:
When a malfunction is found in the the leveling solenoid valve,
replace the height control valve.

NG

Replace height control valve
(See page 

SA–166

).

OK