DTC 31

DTC 31 - OPEN OR SHORT CIRCUIT IN #1 HEIGHT CONTROL VALVE CIRCUIT

CIRCUIT DESCRIPTION
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.

No.1 height control valve is for the front suspension control. It has two solenoid valves to control right hand and left hand pneumatic cylinders separately. No.2 height control valve is for the rear suspension control and consists of two solenoid valves as does No.1 height control valve. Unlike the No.1 solenoid valve, they do not operate separately. In the No.2 height control valve, there is a relief valve to prevent an abnormal pressure build-up inside the air tubes.





Once the ECU stores diagnostic trouble code 31, 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.





*1: When the compressor motor, No.1 and No.2 height control valves and exhaust valve are actuated directly with the height control connector, the ECU stores diagnostic trouble codes 31, 33, 34, 35 or 41 in memory.

*2: When a problem cannot be found by performing the inspection in step [1] and [2], the circuits for the No.1 and No.2 height control valves and the exhaust valve can be judged NORMAL.

DIAGNOSTIC CHART

HINT: Proceed with troubleshooting in accordance with the flow chart shown below, regardless of whether or not diagnostic trouble code 31, 33, 34 or 35 is displayed.
However, if diagnostic trouble codes 31, 33, 34 or 35 were displayed prior to step [1] and [2], check and replace the suspension ECU.





WIRING DIAGRAM

Step 1:

*1: When the compressor motor, No.1 and No.2 height control valves and exhaust valve are actuated directly with the height control connector, the ECU stores diagnostic trouble codes 31, 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 voltage is not applied to terminal 1 of the height control connector.

Step 2:

*2: When a problem cannot be found by performing the inspection in step [1] and [2], the circuits for the No.1 and No.2 height control valves and the exhaust valve can be judged NORMAL. However, if diagnostic trouble codes 31, 33, 34 or 35 were displayed prior to step [1] and [2], check and replace the suspension ECU.

Step 3:

INSPECTION PROCEDURE

HINT 1:
- Proceed with troubleshooting in accordance with the flow chart shown below, regardless of whether or not diagnostic trouble code 31, 33, 34 or 35 is displayed.

HINT 2:
- When diagnostic trouble code 31 is displayed, check the No.1 height control valve circuit.
- When diagnostic trouble code 33 is displayed, check the No.2 height control valve RH circuit.
- When diagnostic trouble code 34 is displayed, check the No.2 height control valve LH circuit.
- When diagnostic trouble code 35 is displayed, check the exhaust valve circuit.

HINT 3:
- If diagnostic trouble code 72 (suspension control actuator power source circuit) is displayed, perform inspection necessary for diagnostic trouble code 72 first.