C1740 - FAULT CODE - OBD2

POST UPDATED IN February, 2023

C1740 Code failures by brands

C1740 LEXUS, TOYOTA: LEFT REAR HEIGHT CONTROL SOLENOID VALVE CIRCUIT

Description of DTC code C1740

The Electronic Suspension Control Unit activates the height control solenoid, which opens the valve and conducts the compressed air to the pneumatic cylinder. This action raises the height of the car. When the vehicle height is low, the ECU energizes the solenoid and the exhaust valve that opens the valve and discharges the compressed air in the pneumatic cylinder into the atmosphere.

The front and rear height control valves have some solenoid valves that control the right and left pneumatic cylinders separately. On the compressor unit you may find the exhaust valve, there is just one valve there.

The diagnostic code C1740 OBDII is set when a malfunction is detected in the left rear height control solenoid valve circuit.

Symptoms of fault code C1740

Causes of OBD2 C1740

The C1740 OBD2 fault code is set for the following reasons:

  • The left rear height control solenoid valve may have damage to its wiring.
  • The left rear height control solenoid valve circuit connections may be in poor condition.
  • The left rear height control solenoid valve may be faulty.
  • Maybe the Electronic Suspension Control Unit is damaged.

Possible solutions of the DTC code C1740

To troubleshoot DTC C1740 OBDII, try this:

  • Consult the TSB (Technical Service Bulletins).
  • Check the wiring related to the Left Rear Height Control Solenoid Valve for burnt or worn wires in the circuit. Also, perform some electrical tests on the circuit and check for deficient voltages. Fix if necessary.
  • Check the left rear height control solenoid. Measure the resistance of the solenoid and verify that it is within the acceptable parameters for proper operation. If you determine that the solenoid is damaged, you may replace it.

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