TOYOTA SEQUOIA 2001 Service Repair Manual

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±699
893 Author: Date:
2005 SEQUOIA (RM1146U)
Input and output signals of each ECU.
Transmitting ECUReceiving ECUSignalCommunication method
ECM

Translate ECU

Suspension control
ECU

Engine speed signal

Transmission signal

Shift position signal

L4 switch signal

TC signal
CAN
Translate ECUSuspension control
ECU
Vehicle wheel speed signal

TS signalCAN
Suspension control ECUTranslate ECUAir suspension setting signalCAN

DIDCN±01
F19465
: CAN
Compressor Assy
Combination Meter
Suspension
Control
ECU Exhaust Solenoid
Valve
Gate Solenoid Valve
Leveling Solenoid ValveAIR SUS Relay
Height Control Cylinder
(Pneumatic Cylinder)
Height Control Sensor
Sub±assy : ECU Output Signal
: ECU Input Signal
: Air Flow Path
Dryer
Height Control Cylinder
(Pneumatic Cylinder)
Speed Sensors

Engine Speed

L4 Switch

Shift Position
Information

Transmission
Model Informa-
tion

Height Control Mode Select
Switch

Height Control Switch

Courtesy Light Switches

Stop Light SwitchHI
N
LO
MAN. DI±700
± DIAGNOSTICSAIR SUSPENSION SYSTEM
894 Author: Date:
2005 SEQUOIA (RM1146U)
SYSTEM DESCRIPTION
1. GENERAL
This system uses pneumatic cylinders instead of the coil springs that are used in a conventional rear
suspension. The suspension control ECU analyzes the information based on the switches, sensors,
and input signals, operates the compressor assy, and uses the solenoid valves to control the vehicle
height.
The suspension control ECU detects, via the height control sensor, the changes in the rear vehicle
height that results from the number of occupants or the amount of the load. Then, the suspension con-
trol ECU controls the height control solenoid valves and the compressor assy in order to automatically
adjust the rear vehicle height to a constant (normal) vehicle height.
Furthermore, three vehicle heights can be selected by operating the height control switch: HI, NOR-
MAL, and LO. The HI vehicle height ensures the vehicle's drive±through performance on rough roads.
The LO vehicle height facilitates the entry and exit of the occupants and the loading and unloading
of cargo. The NORMAL vehicle height helps realize excellent controllability and riding comfort during
normal driving.

± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±701
895 Author: Date:
2005 SEQUOIA (RM1146U)
2. REAR AIR SUSPENSION SYSTEM DESCRIPTION
(a) Auto leveling function
The function to keep the rear vehicle height fixed regardless of the change in the number of the occupants
or the load.
(b) Vehicle height control function
(1) Mode change:
The mode can be changed between the auto mode and the manual mode by operating the
height control mode select switch.
Vehicle height control can be canceled by changing the height control mode select switch
to manual mode.
(2) Auto mode:
Vehicle height can be set to NORMAL, HIGH (+40 mm (1.57 in.)) or LOW (4WD: ±30 mm
(±1.18 in.), 2WD: ±15 mm (±0.59 in.)) by operating the height control switch.
When vehicle speed is 12 km/h (7.46 mph) or less, vehicle height is LOW.
When vehicle speed is 30 km/h (18.64 mph) or less, vehicle height is HIGH.
(3) Manual mode:
Vehicle height can be set in any level within the vehicle height adjustable range by operat-
ing the height control switch.
Vehicle speed is 30 km/h (18.64 mph) or less.
(4) Adjusting time:
Approximately 20 seconds is needed to adjust vehicle height to UP (+40 mm (1.57 in.)).
Approximately 30 seconds is needed to adjust vehicle height to DOWN (±40 mm (±1.18
in.)).
(c) Vehicle speed detection function
When any of the following conditions are met with the vehicle height set to any position other than
NORMAL, vehicle height is automatically adjusted to NORMAL.
AUTO MODE: When vehicle speed is 12 km/h (7.46 mph) or less, vehicle height is LOW.
AUTO MODE: When vehicle speed is 30 km/h (18.64 mph) or less, vehicle height is HIGH.
MANUAL MODE: Vehicle speed is 30 km/h (18.64 mph) or less.
(d) Vehicle height adjustment control after turning the ignition switch off
If the rear vehicle height is raised after the ignition switch is turned off, such as when the occupant gets out
of the vehicle, vehicle height is lowered to the correct position for several seconds even after the ignition
switch is turned off.
(e) Fail±safe
If the vehicle control switch is operated frequently to change vehicle height, vehicle height control is sus-
pended for a while to prevent the compressor from becoming overheated.

DI±702
± DIAGNOSTICSAIR SUSPENSION SYSTEM
896 Author: Date:
2005 SEQUOIA (RM1146U)
3. FUNCTION OF MAIN COMPONENTS
ComponentOutline
Height Control Mode Select SwitchUsed to select vehicle height control mode (Auto/Manual).
Used to operate or stop auto leveling control.
Height Control SwitchAuto mode: Used to select vehicle height (HIGH, NORMAL, LOW).
Manual mode: Used to select vehicle height optionally.
Height Control SensorConverts the vertical change of the rear axle, in proportion to the standard, to sig-
nals and detects vehicle height.
Height Control Indicator Lamp (Combination Meter)Auto mode: Target vehicle height is displayed (HIGH, NORMAL, LOW).
Manual mode: Current vehicle height is displayed (HIGH, NORMAL, LOW).
Height Control Manual Indicator Lamp (Combination Meter)
Comes on during manual mode.
Blinks when the suspension control ECU detects a system malfunction.
Blinks during test mode.
Displays output DTC.
Stop light SwitchDetects braking condition.
Used to clear DTCs.
Pneumatic Cylinder (Height Control Cylinder Assy)Supports the vehicle body and adjusts the vehicle height.
Height Control Compressor Assy (Compressor/Height Con-
trol Dryer)The compressor generates compressed air that is necessary to raise vehicle
height and supplies it to the height control cylinder assy.
The dryer removes moisture from the compressed air.
Exhaust Solenoid ValveDrains the air in the height control cylinder assy when vehicle height is lowered.
(Built into the height control compressor assy)
Leveling Solenoid ValveOpens or closes the passage between the height cylinder assy and height control
compressor assy.
Gate Solenoid ValveOpens or closes the passage between the right and left height control cylinder assy
(Built into the leveling solenoid valve).
Suspension Control ECU
Estimates vehicle condition based on the signals from sensors and switches, and
outputs the control signals to the compressor and valves.
Blinks the height control manual indicator light when a system malfunction is de-
tected.
Air Suspension RelaySupplies power to the height control compressor assy.
Door Courtesy Switch (Body ECU)Detects whether the 5 doors, including the back door, are opened or closed, and
sends the signals to the suspension control ECU.
ECMSends the engine speed signal, etc. to the suspension control ECU through CAN
communication.
Speed Sensor (Skid Control ECU)Sends the vehicle wheel speed signal, etc. to the suspension control ECU through
CAN communication via the translate ECU.

F19466
Compressor Motor Exhaust Solenoid
ValveDryer
Compressor Portion
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±703
897 Author: Date:
2005 SEQUOIA (RM1146U)
4. CONSTRUCTION AND OPERATION OF MAIN COMPONENTS
Compressor Assy
The compressor and motor are used to make the compressed air necessary for raising the vehicle
height.
The exhaust solenoid valve is provided on the compressor assy. The exhaust solenoid valve dis-
charges compressed air from the pneumatic cylinders to the atmosphere in order to lower the vehicle.
The dryer is used to eliminate the moisture in the compressed air made by the compressor and motor.
To protect the battery, this compressor assy operates only when the engine is running.
Specification
MotorTypeDC
MotorRated Voltage12 V
Exhaust Solenoid ValveRated Voltage12 V
Exhaust Solenoid ValveOperating Voltage Range10 to 15 V
Exhaust Solenoid ValveResistance10 to 14 W

F19467
Height Control Cleaner
Exhaust Chamber
OUT IN
F19468
Compressed Air DI±704
± DIAGNOSTICSAIR SUSPENSION SYSTEM
898 Author: Date:
2005 SEQUOIA (RM1146U)
Height Control Cleaner
The height control cleaner consists of a filter to remove dust and debris, and an expansion chamber
to reduce the intake sound. In consideration of dusty areas, this cleaner draws air from the inside of
the vehicle cabin.
This cleaner cannot be disassembled; therefore, it is not possible to replace only the filter element.
Height Control Cylinder Assy (Pneumatic Cylinder)
The pneumatic cylinder consists of a signal type air chamber with a large compressed air capacity in order
to realize excellent riding comfort.

F19469
Gate Solenoid Valve
Leveling Solenoid Valve
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±705
899 Author: Date:
2005 SEQUOIA (RM1146U)
Height Control Valve
The height control valve consists of a leveling solenoid valve, and gate solenoid valve.
Specification
Leveling Solenoid ValveRated Voltage12 V
Leveling Solenoid ValveOperating Voltage Range10 to 15 V
Leveling Solenoid ValveResistance10 to 14 W
Gate Solenoid ValveRated Voltage12 V
Gate Solenoid ValveOperating Voltage Range10 to 15 V
Gate Solenoid ValveResistance17.5 to 21.5 W

F19470
Low
High
Link
Arm
DI±706
± DIAGNOSTICSAIR SUSPENSION SYSTEM
900 Author: Date:
2005 SEQUOIA (RM1146U)
Height Control Sensor
The height control sensor detects the vehicle height. One sensor is located in the center of the rear
frame, which is connected to the center of the rear axle via a link, in order to detect the vehicle height.
The sensor has an arm that moves along with the change in vehicle height, and the resultant change
in voltage enables the suspension control ECU to detect the vehicle height.
A semiconductor type sensor has been adopted to make it compact and heat±resistant.
HINT:
Refer to the following factors when adjusting the link of the height control sensor:
The vehicle height changes approximately 4 mm (0.16 in.) with each turn of the link.
The vehicle height changes approximately 2 mm (0.08 in.) by moving the link installation position by
1 mm (0.04 in.).

DIDCP±01
± DIAGNOSTICSAIR SUSPENSION SYSTEM
DI±707
901 Author: Date:
2005 SEQUOIA (RM1146U)
HOW TO PROCEED WITH TROUBLESHOOTING
1 Vehicle Brought to Workshop
NEXT
2 Customer Problem Analysis (See page DI±710)
NEXT
3 Check CAN Communication System (See page DI±1065)
Check if any DTCs are output.
HINT:
The suspension control ECU of this system is connected to the CAN communication system. Therefore, be-
fore starting troubleshooting, make sure to check that there is no trouble in the CAN communication system.
CAN System DTC is Output (Proceed To ºCAN
COMMUNICATION SYSTEMº (See page
DI±1065))
No CAN System DTC is Output (Go to step 4)
4 Check and Clear DTCs (See page DI±723)
NEXT
5 Problem Symptom Confirmation
Symptom Does Not Occur (Go to step 6)
Symptom Occurs (Go to step 7)

DI±708
± DIAGNOSTICSAIR SUSPENSION SYSTEM
902 Author: Date:
2005 SEQUOIA (RM1146U)
6 Symptom Simulation (See page IN±35)
NEXT
7 DTC Check (See page DI±723), Test Mode (See page DI±711)
Normal System Code (Go to step 8)
Trouble Code (Go to step 9)
8 Problem Symptoms Table (See page DI±716)
NEXT Go To Step 10
9 DTC Chart (See page DI±729)
NEXT
10 Circuit Inspection (See page DI±731 to DI±793)
NEXT
11 Identification of Problem
NEXT
12 Repair
NEXT