TOYOTA SEQUOIA 2001 Service Repair Manual

F16805
Suspension Control ECU
Wire Harness View:
S25
SLRL
F19436
Height Control Valve
Wire Harness View:
H16
321
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±739
933 Author: Date:
2005 SEQUOIA (RM1146U)
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±R4
BM1SLRR 313
IN13
S25
BI W±B 2LG±R
LG±R DI±740
± DIAGNOSTICSAIR SUSPENSION SYSTEM
934 Author: Date:
2005 SEQUOIA (RM1146U)
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 ConditionTrouble 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

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±741
935 Author: Date:
2005 SEQUOIA (RM1146U)
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 ºLEVEL SOL REARº in the ACTIVE TEST, and operate it with the hand±held tester.
AIR SUSPENSION:
ItemVehicle Condition / Test DetailsDiagnostic Note
LEVEL SOL REARTurn leveling solenoid valve / ON or OFFOperation 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:
NGA
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:
32 1
DI±742
± DIAGNOSTICSAIR SUSPENSION SYSTEM
936 Author: Date:
2005 SEQUOIA (RM1146U)
2 Inspect leveling solenoid valve (height control valve).
PREPARATION:
Disconnect the valve connector.
CHECK:
Measure the resistance between terminals.
OK:
Solenoid valveTester connectionResistance
Leveling solenoid valve2 ± 310 to 14 W
CHECK:
Check the operating sound of the valves when battery voltage
is applied to the terminals as shown below.
Solenoid valveBattery positiveBattery negative
Leveling solenoid valve32
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

F16805
S25
Suspension Control ECU
Wire Harness View:
SLRR
F19436
Height Control Valve
Wire Harness View:
H16
321
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±743
937 Author: Date:
2005 SEQUOIA (RM1146U)
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 3 of the height control valve and ter-
minal S25±3 (SLRR) 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).

F19455
Suspension Control ECU Exhaust Solenoid Valve
(Height Control Compressor)
L±R5
BM2SLEX 14
IN11
S25
BI W±B 2 H14
H14L±R L±R DI±744
± DIAGNOSTICSAIR SUSPENSION SYSTEM
938 Author: Date:
2005 SEQUOIA (RM1146U)
DTC C1735/35 Exhaust Solenoid Valve Circuit
CIRCUIT DESCRIPTION
The suspension control ECU operates the exhaust solenoid valve (height control compressor), releases the
air from the height control cylinder assy (pneumatic cylinder), and lowers vehicle height.
When the vehicle height is lowered, the suspension control ECU opens the height control valve and then
operates the exhaust solenoid valve to release the compressed air to the outside.
The exhaust solenoid valve is on the compressor unit and has only one valve.
DTC No.DTC Detecting ConditionTrouble Area
C1735/35
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.

Exhaust solenoid valve (Height control compressor)

Exhaust solenoid valve (Height control compressor) circuit

Suspension control ECU
HINT:

Once the ECU stores DTC C1735/35 in the memory, the vehicle height control is suspended until a
normal signal is input to the ECU from the exhaust solenoid valve. However, control is resumed if the
ignition switch is turned OFF, then ON again.

Malfunction in the exhaust solenoid valve:
The height control indicator lamp ºNº comes on or blinks, and ºHIº and ºLOº do not come on by operating
the height control switch ºUPº or ºDOWNº.
WIRING DIAGRAM
DIDDS±01

F19457
Connector Front View:
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±745
939 Author: Date:
2005 SEQUOIA (RM1146U)
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.)
1 Inspect exhaust solenoid valve (height control compressor).
PREPARATION:
Disconnect the valve connector.
CHECK:
Measure the resistance between terminals.
OK:
Solenoid valveTester connectionResistance
Exhaust solenoid valve1 ± 210 to 14 W
CHECK:
Check the operating sound of the valves when battery voltage
is applied to the terminals as shown below.
Solenoid valveBattery positiveBattery negative
Exhaust solenoid valve12
OK:
Operating sound (clicking) can be heard.
HINT:
When a malfunction is found in the exhaust solenoid valve, re-
place the height control compressor.
NG Replace height control compressor assy
(See page SA±162).
OK

F16805
S25
Suspension Control ECU
Wire Harness View:
SLEX
F19459
Height Control Compressor
Connector Front View:
H14
DI±746
± DIAGNOSTICSAIR SUSPENSION SYSTEM
940 Author: Date:
2005 SEQUOIA (RM1146U)
2 Check harness and connector (Height control compressor ± 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 compressor
and terminal S25±1 (SLEX) 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 compressor 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).

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±747
941 Author: Date:
2005 SEQUOIA (RM1146U)
DTC C1741/41 Air Sus Relay Circuit
CIRCUIT DESCRIPTION
When the ºUPº 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 ConditionTrouble 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
H131
Engine Room R/B No. 2
G±Y AIR SUS Relay
Battery J28
J/C W
BM21
IC48
IA121
WWW
2
22
2 3
25
1W
9B
5
W±B
J8
J/C
AAW±B
1K12
1F9
A W±B
IESuspension
Control
ECU
IA125
G±Y
S255
RC F10
Fusible Link Block
ALT
Instrument
Panel J/BAIR SUS DI±748
± DIAGNOSTICSAIR SUSPENSION SYSTEM
942 Author: Date:
2005 SEQUOIA (RM1146U)
WIRING DIAGRAM