2001 TOYOTA SEQUOIA Page 18

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±749
943 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 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 ºMOTOR RELAYº in the ACTIVE TEST, and operate it with the hand±held tester.
AIR SUSPENSION:
ItemVehicle Condition / Test DetailsDiagnostic Note
MOTOR RELAYTurn AIR SUS relay / ON or OFFOperation 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:
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

F16805
S25
Suspension Control ECU
Wire Harness View:
RC
F19460
Engine Room R/B No. 2:
AIR SUS
Relay Terminal
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±751
945 Author: Date:
2005 SEQUOIA (RM1146U)
3 Check harness and connector (Engine room R/B ± Suspension control ECU,
Body ground).
PREPARATION:
Disconnect the ECU connector.
CHECK:
Check for an open or short circuit in the harness and the con-
nector between the AIR SUS relay terminal 1 of the engine
room R/B and terminal S25±5 (RC) 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 connector be-
tween the AIR SUS relay terminal 2 of the engine room R/B 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).

F19435
1 (+)
2 (±)
Connector Front View:
43
DI±754
± DIAGNOSTICSAIR SUSPENSION SYSTEM
948 Author: Date:
2005 SEQUOIA (RM1146U)
INSPECTION PROCEDURE
1 Inspect height control compressor.
PREPARATION:
(a) Disconnect the height control compressor connector.
(b) Connect the positive (+) lead from the battery to terminal
1 and the negative (±) lead to terminal 2.
CHECK:
Apply battery voltage between terminals 1 and 2 of the height
control compressor.
OK:
Compressor motor operates.
NOTICE:

Do not operate the height control compressor assy
for 90 sec. or more.

Since a short and lock inside the height control com-
pressor assy causes enormous current to flow, stop
the operation immediately when it does not rotate.
CHECK:
Check continuity between each terminal of the height control
compressor.
OK:
Terminal No.Specified condition
2 ± 4Continuity
3 ± 4Continuity
NG Replace height control compressor
(See page SA±162).
OK

F19461
Height Control Compressor
Connector Front View:
H13
DI±756
± DIAGNOSTICSAIR SUSPENSION SYSTEM
950 Author: Date:
2005 SEQUOIA (RM1146U)
3 Check harness and connector (Height control compressor ± Battery, Body
ground).
PREPARATION:
(a) Reconnect the ECU connector.
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage according to the value(s) in the table be-
low.
OK:
Tester connectionConditionSpecified value
H13±1 ± Body ground
Engine idling, height con-
trol switch is pushed from
ºNº to ºUPº
10 to 14 V
HINT:
Measure the voltage within 90 seconds.
CHECK:
Measure the resistance according to the value(s) in the table
below.
OK:
Tester connectionConditionSpecified value
H13±2 ± Body groundAlwaysBelow 1 W
NG Repair or replace harness or connector.
OK
Replace suspension control ECU
(See page IN±35).

± 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

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