C1744

SUSPENSION CONTROL: AIR SUSPENSION SYSTEM: C1733/33: Rear Height Control Gate Solenoid Valve Circuit Malfunction

DTC C1733/33 - Rear Height Control Gate Solenoid Valve Circuit Malfunction

DTC C1734/34 - Rear Height Control Leveling Solenoid Valve Circuit Malfunction

DTC C1735/35 - Exhaust Solenoid Valve Circuit

DTC C1744/44 - Tank Solenoid Valve Circuit

DESCRIPTION

The suspension control ECU opens the height control valve to lead the compressed air to the height control cylinder (pneumatic cylinder) and to raise the vehicle height.
When the vehicle height is lowered, the suspension control ECU opens the height control valve to store the compressed air in the low pressure tank temporarily, and then operates the exhaust solenoid valve to release the compressed air to the outside.
Further, the height control solenoid valve (gate solenoid valve) opens and closes the passage between the right and left pneumatic cylinder.
The height control valve is on the low pressure tank and consists of 3 valves in total, leveling solenoid valve, gate solenoid valve and tank solenoid valve.
The leveling solenoid valve opens and closes the passage between the compressor and the pneumatic cylinder. The gate solenoid valve opens and closes the passage between the right and left pneumatic cylinder. The tank solenoid valve opens and closes the passage between pneumatic cylinder and the low pressure tank. The exhaust solenoid valve is on the compressor unit and has only one valve.





HINT:
- Once the ECU stores DTC C1733/33, C1734/34, C1735/35 or C1744/44 in the memory, the vehicle height control is suspended out until a normal signal is input to the ECU from the height control solenoid valves and the exhaust solenoid valve. However, control is resumed if the ignition switch is turned OFF, then ON again.
- Malfunction in the gate solenoid valve and the leveling solenoid valve:
The height control operation is suspended, and the height control indicator light does not change by operating the height control switch.
- Malfunction in the exhaust solenoid valve:
The vehicle height is lowered to the normal height within 30 sec., and then the height control operation is suspended. The height control indicator light "N" comes on or blinks, and that of "HI" and "LO" do not illuminated by operating the height control switch "UP" and "DOWN".
- Abnormality of the tank solenoid valve:
Although the height control is still possible, the vehicle lowering speed may be slower.

WIRING DIAGRAM





INSPECTION PROCEDURE
HINT:
- Proceed to troubleshooting following the flow chart, regardless of whether or not DTC C1733/33, C1734/34, C1735/35 or C1744/44 is displayed.
- If DTC C1761/61 (ECU malfunction) and/or C1774/74 (power source circuit) is displayed, perform the inspection necessary for DTC C1761/61 Air Suspension System and/or C1774/74 Air Suspension System first.
(If DTC C1761/61 and the 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 Techstream, and start from step 2 when not using the Techstream.
- Since the exhaust solenoid valve cannot be tested in Active Test, start the inspection from step 2.

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and the Techstream on.
(c) Select the item "Rear Leveling Solenoid", "Rear Gate Solenoid", "Low Pressure Tank Solenoid", "Exhaust Solenoid" in the Active Test, and operate it with the Techstream.
(d) Check whether the solenoid makes sound.
(e) Check whether the height control valve has continuity (will vibrate).
OK:
The solenoid makes sound, and the height control valve has continuity (will vibrate).
OK -- REPLACE SUSPENSION CONTROL ECU
NG -- Continue to next step.
2. INSPECT HEIGHT CONTROL VALVE OR EXHAUST SOLENOID VALVE





(a) Disconnect the valve connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:





HINT: The height control solenoid valve has 2 connectors.
- The gate solenoid valve and the leveling solenoid valve have a 3-pole connector.
- Tank solenoid valve connector has a 2-pole connector.
(c) Check the operating sound of the valves when battery positive voltage is applied to the terminals as shown below.






OK:
It should make an operating sound (click).
HINT:
- When a malfunction is found in the gate solenoid valve, the leveling valve or the tank solenoid valve, replace the height control reservoir assembly.
- When a malfunction is found in the exhaust solenoid valve, replace the height control compressor assembly.

NG -- REPLACE HEIGHT CONTROL COMPRESSOR ASSEMBLY
NG -- REPLACE HEIGHT CONTROL RESERVOIR ASSEMBLY
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR
(a) Check for open and short circuit in the harness and the connectors between height control solenoid valve or the exhaust solenoid valve and the suspension control ECU Electronic Circuit Inspection Procedure.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE SUSPENSION CONTROL ECU