TOYOTA SEQUOIA 2001 Service Repair Manual

± 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

F19458
DI±750
± DIAGNOSTICSAIR SUSPENSION SYSTEM
944 Author: Date:
2005 SEQUOIA (RM1146U)
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 connectionResistance
3 ± 510 kW or higher
3 ± 5
Below 1 W
(When battery voltage is applied to ter-
minals 1±2)
NG Replace AIR SUS relay.
OK

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).

DI±752
± DIAGNOSTICSAIR SUSPENSION SYSTEM
946 Author: Date:
2005 SEQUOIA (RM1146U)
DTC C1742/42 Height Control Compressor Circuit
CIRCUIT DESCRIPTION
When the ºUPº side of the height control is pressed, a signal is sent from terminal RC of the suspension con-
trol ECU to switch the AIR SUS relay ON. As a result, the relay contacts close and the compressor motor
turns on, producing compressed air.
The suspension control ECU detects the amount of current flow to the compressor motor by means of the
differences in potential at terminals RM+ and RM± of the suspension control ECU. In this way, the suspen-
sion control ECU monitors the compressor circuit for abnormalities.
DTC No.DTC Detecting ConditionTrouble Area
C1742/42
With the AIR SUS relay activated, a lock, open or short signal
of the height control compressor motor is detected for 4 sec. or
more.
Height control compressor assy

Height control compressor circuit

Suspension control ECU
HINT:
Once the ECU stores DTC C1742/42 in the memory, the vehicle height control is not carried out until the
normal signal is input to the ECU from the compressor motor. However, the control automatically resumes
approx. 70 min. after the ignition switch is turned ON.
DIDDU±01

F19444
Height Control Compressor
(Compressor/Height Control Dryer)
H133
Engine Room R/B No. 2
W±B
Battery J28
J/CR±L
BM23
IN115
S2520
2
3
25
1W
9B
5
J8
J/C
AAW±B
1K12
1F9
A W±B
IESuspension
Control
ECU
RC F10
Fusible Link Block
AIR SUS
Instrument
Panel J/BRM+ R±L R±L
H134
BR±Y
BM24
IA121S2521
BR±Y BR±Y
RM±
AIR SUS Relay H131
W
BM21
IC48
WW W
22
2 S255
G±Y IN16
IA125
G±Y
BJ H132
BM22
W±B
AJ19
J/C W±BALT
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±753
947 Author: Date:
2005 SEQUOIA (RM1146U)
WIRING DIAGRAM

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

F16805
Suspension Control ECU
Wire Harness View:
S25
RM+
RM±
F19461
Height Control Compressor
Connector Front View:
H13
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±755
949 Author: Date:
2005 SEQUOIA (RM1146U)
2 Check harness and connector (height control compressor ± Suspension control
ECU).
PREPARATION:
Disconnect the ECU connector.
CHECK:
Check for an open or short circuit in the harness and the con-
nector between terminals 3 and 4 of the height control compres-
sor and terminals S25±20 (RM+) and S25±21 (RM±) of the sus-
pension control ECU.
OK:
There is no open or short in the wire harness.
NG Repair or replace harness or connector.
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