DTC 31

The ECU energizes the height control valve solenoid, which opens the valve and leads compressed air to the pneumatic cylinder, thus raising the vehicle height.

When lowering the vehicle height, the ECU energizes not only the height control valve solenoid but also the exhaust valve solenoid which open the valve and discharge the compressed air in the pneumatic cylinder to the atmosphere.

Front and rear height control valves have two solenoid valves to control right hand and left hand pneumatic cylinders separately.

The exhaust valve is located on the compressor unit, and has one solenoid valve only.

Code 31 corresponds to the front RH height control valve circuit.

Once the ECU stores diagnostic trouble code 31, 32, 33, 34 or 35 in memory, vehicle height control is not carried out until a normal signal is input to the ECU from the height control valves and exhaust valve. However, control is resumed if the ignition switch is turned off, then on again.

Hint:
If diagnostic trouble code 74 (power source circuit) is displayed, perform inspection necessary for diagnostic trouble code 74 first.
DTC 74

Wiring Diagram:

Inspection Procedure - Step 1:

Step 2:

Step 3:

*1: When the compressor motor, front and rear height control valves and exhaust valve are actuated directly with the height control connector, the ECU stores diagnostic trouble codes 31, 32, 33, 34, 35 or 41 in memory. Furthermore, if the vehicle height is not raised or lowered in step [1] , it may be possible that battery positive voltage is not applied to terminal 3 of the height control connector.

*2: When a problem cannot be found by performing the inspection in step [1] and [2] , the circuits for the front and rear height control valves and exhaust valve can be judged NORMAL.
However, if diagnostic trouble codes 31, 32, 33, 34 or 35 were displayed prior to step [1] and [2] check and replace the suspension ECU.