2001 TOYOTA SEQUOIA height

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±757
951 Author: Date:
2005 SEQUOIA (RM1146U)
DTC C1751/51 Continuous Electric Current To Height Con-
trol Compressor
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
C1751/51*1With the AIR SUS relay activated, the vehicle does not go up
to the standard vehicle height after the 90 sec. have elapsed.

Height control compressor assy

Height control compressor circuit

Height control sensor circuit

Height control sensor sub±assy

Relief valve

AIR SUS relay circuit

Air leakage from the air tube or each valve

Clogging in the air tube or each valve

Suspension control ECU
*1: The compressor motor operates continuously to raise vehicle height and allows electric current flow to
the AIR SUS relay for 90 seconds or more under the following conditions:

Vehicle height control is attempted on a steep slope when the vehicle is overloaded.

The compressor remains on for an excessive period of time or repeatedly turns on and off because
of continuous height control switch operation.

If the compressor remains on because the vehicle is jacked up, the vehicle height is set at a position
lower than normal while the engine is running and then the vehicle height control function raises the
vehicle.
Thus DTC C1751/51 may be output and vehicle height control may be suspended. (This is not electrically
abnormal.) In this case, however, the vehicle height operation is resumed approx. 10 min. after the ignition
switch is turned ON after the ECU detects the first error. If ECU detects another error, it takes 70 minutes
until control is resumed.
WIRING DIAGRAM
See page DI±752.
DIDDV±01

DI±758
± DIAGNOSTICSAIR SUSPENSION SYSTEM
952 Author: Date:
2005 SEQUOIA (RM1146U)
INSPECTION PROCEDURE
1 Inspect height control compressor circuit (See page DI±752).
NEXT
2 Inspect air leakage (See page SA±156).
CHECK:
Check tube connections for air leakage.
OK:
No leaks
NG Repair or replace air tube.
OK

F19437
Height Control Valve
Connector Front View:
32 1
F19457
Height Control Compressor
Connector Front View:
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±759
953 Author: Date:
2005 SEQUOIA (RM1146U)
3 Inspect height control valve (Gate solenoid valve, Leveling solenoid valve) or
height control compressor (Exhaust solenoid valve).
When 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, ºGATE 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
GATE SOL REARTurn gate solenoid valve / ON or OFFOperation sound of solenoid (clicking sound) can
be heard
HINT:
The exhaust solenoid valve cannot be tested in ACTIVE TEST.
CHECK:
(a) Check whether the solenoid makes a sound.
(b) Check whether the height control solenoid valve has continuity (will vibrate).
OK:
The solenoid makes a sound, and the height control solenoid valve has continuity. (It will vi-
brate.)
When not using hand±held tester:
PREPARATION:
Disconnect the valve connector.
CHECK:
Check the operating sound of the valves when battery positive
voltage is applied to the terminals as shown below.
Solenoid valveBattery positiveBattery negative
Height control valve
(Gate solenoid valve)12
Height control valve
(Leveling solenoid valve)32
Height control compressor
(Exhaust solenoid valve)12
OK:
It make an operating sound (click).
HINT:

When a malfunction is found in the gate solenoid valve,
replace the leveling valve and the height control valve.

When a malfunction is found in the exhaust solenoid
valve, replace the height control compressor assy.

DI±760
± DIAGNOSTICSAIR SUSPENSION SYSTEM
954 Author: Date:
2005 SEQUOIA (RM1146U)
NG Replace height control valve assy
(See page SA±162).
NG Replace height control compressor assy
(See page SA±162).
OK
4 Inspect height control sensor sub±assy.
CHECK:
Inspect and adjust the height control sensor sub±assy (See page SA±156).
NEXT
5 Reconfirm DTC.
CHECK:
Clear the DTC and repeat the procedure to re±check it (See page DI±729).
HINT:
If the DTC C1751/51 is still output, proceed to the next step.
NEXT
Check and repair or replace malfunctioning
parts.
(a) Air tube is clogged (See page SA±156).
(b) Compressor is faulty (See page SA±162).
(c) Relief valve is faulty (See page SA±166).
(d) Height control sensor sub±assy is faulty (See page SA±156).
(e) Foreign material entered the height control solenoid valve (gate solenoid valve) and the exhaust sole-
noid valve.
(f) Air leakage due to damage to the height control cylinder assy (pneumatic cylinder).
(g) Suspension control ECU malfunctions (See page IN±35).

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±761
955 Author: Date:
2005 SEQUOIA (RM1146U)
DTC C1761/61 ECU Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
C1761/61Suspension control ECU malfunction

Power source circuit

Suspension control ECU

Communication circuit
INSPECTION PROCEDURE
HINT:

If DTC C1774/74 (power source circuit) is displayed, perform the inspection necessary for DTC
C1774/74 first (See page DI±763).

If DTC U0122/67, U0100/65, U0132/71 and C1761/61 (ECU malfunction) are output at the same time,
perform the inspection necessary for the CAN communication system first.

The suspension control ECU, controlling the air suspension system, is activated when the ignition
switch is turned ON.
After 2 seconds, the ºMAIN RELAYº built in the ECU is activated and the system is driven by +B power
source.
Vehicle height may increase after turning the ignition switch off and unloading the vehicle/letting
people get out of the vehicle. In order to adjust the vehicle height, vehicle height control will continue
for a while from then.
DIDDY±01

F19448
H12
Height Control SwitchSuspension Control
ECU
IMS25 313
S25 HI
LOHSW
LW S
DNSW 32
4 2 W±BUPSW
W L±B
E DI±774
± DIAGNOSTICSAIR SUSPENSION SYSTEM
968 Author: Date:
2005 SEQUOIA (RM1146U)
DTC C1786/86 Height Control Switch Circuit
(Test Diagnosis)
CIRCUIT DESCRIPTION
Vehicle height can be chosen by pressing the height control switch.
By pressing the ºUPº side, vehicle height goes up.
By pressing the ºDOWNº side, vehicle height goes down.
HINT:
This DTC is output only when the sensor signal check is done.
DTC No.DTC Detecting ConditionTrouble Area
C1786/86Height control switch signal does not change.

Height control switch

Height control switch circuit

Suspension control ECU
WIRING DIAGRAM
DIDED±01

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±775
969 Author: Date:
2005 SEQUOIA (RM1146U)
INSPECTION PROCEDURE
HINT:
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 Read value of the hand±held tester.
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Turn the ignition switch ON, and turn the hand±held tester main switch ON.
(c) Select the item ºHEIGHT SW DOWNº or ºHEIGHT SW UPº in the DATA LIST, and read its value dis-
played on the hand±held tester.
AIR SUSPENSION:
ItemMeasurement Item / Range (Dis-
play)Normal ConditionDiagnostic Note
HEIGHT SW DOWNHeight control switch (DOWN) /
ON or OFFON: Height control switch
ºDOWNº button is pressed
OFF: ±
±
HEIGHT SW UPHeight control switch (UP) / ON or
OFFON: Height control switch ºUPº
button is pressed
OFF: ±
±
CHECK:
Check that the value displayed on the hand±held tester changes by pressing the height control switch ºUPº
or ºDOWNº.
OK:
Height control switch value changes.
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

F19433
3
UP Button
DOWN Button
Height Control
Switch
12 45
DI±776
± DIAGNOSTICSAIR SUSPENSION SYSTEM
970 Author: Date:
2005 SEQUOIA (RM1146U)
2 Inspect height control switch.
PREPARATION:
Remove the height control switch connector.
CHECK:
Check continuity between each terminal of the height control
switch when the height control switch ºUPº or ºDOWNº button
is pressed.
OK:
Tester connectionSwitch conditionSpecification
ºUPº button2 ± 3Continuity
ºDOWNº button2 ± 3No continuity
ºUPº button2 ± 4No continuity
ºDOWNº button2 ± 4Continuity
NG Replace height control switch.
OK