C1742

SUSPENSION CONTROL: AIR SUSPENSION SYSTEM: C1742/42: Height Control Compressor Circuit

DTC C1742/42 - Height Control Compressor Circuit

DESCRIPTION

When the "UP" side of the height control switch is pressed, a signal is sent from terminal RC of the suspension control 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 suspension control ECU monitors the compressor circuit for abnormalities.





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.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK DTC
(a) Check if the other DTC is recorded Air Suspension System.
Result:






B -- REPAIR CIRCUIT INDICATED BY OUTPUT DTC
A -- Continue to next step.
2. INSPECT HEIGHT CONTROL COMPRESSOR ASSEMBLY




(a) Disconnect the height control compressor assembly connector.
(b) Apply battery voltage between terminal 1 and 2 of the height control compressor assembly.
Standard:
Compressor motor operates.
NOTICE:
- Do not operate the height control compressor assembly 90 sec. or more.
- Since short and lock inside the height control compressor assembly causes enormous current to flow, stop the operation immediately when it dose not rotate.

NG -- REPLACE HEIGHT CONTROL COMPRESSOR ASSEMBLY
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (HEIGHT CONTROL COMPRESSOR ASSEMBLY - SUSPENSION CONTROL ECU)
(a) Check for open and short circuit in the harness and the connector between the height control compressor assembly and the suspension control ECU Electronic Circuit Inspection Procedure.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (HEIGHT CONTROL COMPRESSOR ASSEMBLY - AIR SUS RELAY)
(a) Check for open and short circuit in the harness and the connector between the height control compressor assembly and the AIR SUS relay Electronic Circuit Inspection Procedure.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
5. INSPECT HEIGHT CONTROL SOLENOID VALVE OR EXHAUST SOLENOID VALVE
(a) When using the Techstream:
(1) Connect the Techstream to DLC3.
(2) Turn the ignition switch ON and the Techstream on.
(3) 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.
(4) Check whether the solenoid makes sound.
(5) Check whether the height control solenoid valve has a continuity (will vibrate).
OK:
The solenoid makes sound, the height control solenoid valve has a continuity (will vibrate).




(b) When not using the Techstream:
(1) Disconnect the valve connector.
(2) 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).
- 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.
6. CHECK AIR TUBE CLOGGED
(a) Check visually for clog, damage or breakage on the air tube Adjustments.
NG -- REPAIR OR REPLACE AIR TUBE
OK -- REPLACE SUSPENSION CONTROL ECU