LEXUS LS430 2003 Factory Repair Manual

Fig. 3: Air Suspension System Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
1.AIR SUSPENSION SYSTEM DESCRIPTION

a. The suspension control ECU operates the compressor & motor with the dryer and uses the solenoid
valves to control the vehicle height by analyzing the information based on the switches, sensors and
input signals.
b. Through the 4 height control sensors, the suspension control ECU detects the changes in the vehicle
height that results from the number of occupants or the amount of the load. Then, the suspension
control ECU controls the height control solenoid valves and the compressor & motor with the dryer
in order to automatically adjust the vehicle height to a constant (normal) level.
c. Furthermore, two vehicle heights can be selected by operating the height control switch: HI and
Normal.
d. In cases such as when the vehicle is jacked up, the auto leveling function is prohibited by turning
the ignition switch off.
If the vehicle is raised with its engine running, connect terminals OPB and CG of the DLC3 so the
vehicle height control is not carried out.
e. The absorber control switch selects the shock absorber damping force (normal or sport).
f. w/ Pre-collision safety system:
The suspension control ECU changes the stiffness of the suspension to the hardest setting by
receiving signals (collision unavoidable) from the cruise control ECU.
Function of Components

Fig. 4: Function Of Components
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
The hand-held tester can be used at steps 5, 8 and 11.
1.VEHICLE BROUGHT TO WORKSHOP
2.(SEE CUSTOMER PROBLEM ANALYSIS CHECK
)
3.PROBLEM SYMPTOM CONFIRMATION
SYMPTOM DOES NOT OCCUR (Go to step 4)
SYMPTOM OCCURS (Go to step 5)
4.SYMPTOM SIMULATION (SEE HOW TO PROCEED WITH TROUBLESHOOTING
)
5.(SEE DTC CHECK/CLEAR
)
NORMAL SYSTEM CODE (Go to step 6)

TROUBLE CODE (Go to step 7)
6.(SEE PROBLEM SYMPTOMS TABLE
)
7.(SEE DIAGNOSTIC TROUBLE CODE CHART
)
8.CIRCUIT INSPECTION (SEE DTC C1711 RIGHT FRONT HEIGHT CONTROL SENSOR
CIRCUIT, DTC C1712 LEFT FRONT HEIGHT CONTROL SENSOR CIRCUIT,DTC C1713
RIGHT REAR HEIGHT CONTROL SENSOR CIRCUIT, DTC C1714 LEFT REAR HEIGHT
CONTROL SENSOR CIRCUIT to TD TERMINAL CIRCUIT )
9.IDENTIFICATION OF PROBLEM
10.REPAIR
11.CONFIRMATION TEST
END

Fig. 5: Air Suspension System Check Sheet
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
1.TEST MODE

HINT:
By switching from normal mode into test mode, you can inspect the height control switch, absorber
control switch, front acceleration sensor and rear acceleration sensor.
When entering the test mode, the suspension control ECU sets all the test mode DTCs first.
After completing the test mode for each check item, the test mode DTCs that are determined
normal by the suspension control ECU will be erased.
The test mode DTCs for other check items may not be erased when only a certain signal is
inspected.
When the test mode returns back to the normal mode, all the test mode DTCs will be erased.
a. Procedure for Test Mode.
1. Make sure that the ignition switch is off.
2. Set each of the check items to the condition in Operation (A) in the Test mode table below.
3. Connect the hand-held tester to the DLC3.
4. Turn the ignition switch to the ON position.
5. Select the SIGNAL CHECK mode on the hand-held tester.
6. Set each of the check items to the condition in Operation (B) in the Test mode table below.

Fig. 6: Connecting Hand-Held Tester To DLC3
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
TEST MODE
HINT:
In step (6), all signals can be checked together.
Check ItemOperation (A)Operation (B)
Height control switchNORM
positionHIGH position
Absorber control
switch-Slowly move the absorber control switch "NORM"
<--> "SPORT" both ways once
Right front acceleration
sensor-Keep the vehicle still without any vertical
movement for 1 second
Left front acceleration
sensor-Keep the vehicle still without any vertical
movement for 1 second
Rear acceleration
sensor-Keep the vehicle still without any vertical
movement for 1 second

7. Read the test mode DTCs by following the prompts on the tester screen.
HINT:
Refer to the hand-held tester operator's manual for further details.
DTC of Air Suspension System test mode function:
If a malfunction code is displayed during the test mode DTC check, check the circuit listed
for that code. For details of each code, refer to "See Procedure" under the respective "DTC
No." in the chart.
Fig. 7: DTC Of Air Suspension System Test Mode Function

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
8. After completing the test mode, disconnect the tester and turn the ignition switch off.
If a normal system code is displayed during the DTC check but the problem still occurs, check the circuits for
each problem s
ymptom in the order given in the table below and proceed to the relevant troubleshooting page.

Fig. 8: Problem Symptoms Table
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
HINT:
Inspect the connectors from the back side while connectors are connected.
SUSPENSION CONTROL ECU:
Fig. 9: Identifying Suspension Control ECU Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
TERMINALS NUMBER AND SPECIFIED CONDITION
Symbols
(Terminals No.)Wiring
ColorTerminal DescriptionConditionSpecified
Condition
B (A20-1) - GND
(A20-4)W-R - W-
BBatteryAlways10 to 14 V
VT (A20-3) -
GND (A20-4)Y - W-B
Absorber control
indicator lamp output
signalIG switch ON, absorber control
switch "SPORT"0 to 1.5 V
VT (A20-3) -
GND (A20-4)Y - W-B
Absorber control
indicator lamp output
signalIG switch ON, absorber control
switch "NORM"10 to 14 V
GND (A20-4) -
Body groundW-B -
Body
ground
GroundAlwaysBelow 1
ohms
SLEX (A20-5) -
GND (A20-4)V-Y - W-BExhaust solenoid valveIG switch ONBelow 1 V
SLEX (A20-5) -
GND (A20-4)V-Y - W-BExhaust solenoid valveEngine idling, absorber control
switch from "HIGH" to "NORM"8 V or more
RC (A20-6) -
GND (A20-4)Y-R - W-BAIR SUS relayIG switch ONBelow 1 V