POST UPDATED IN January, 2023

P1801 Code failures by brands


Description of DTC code P1801

The variable intake air system has a solenoid that is responsible for creating interruptions in the multiple vacuum signal voltage, thereby regulating valve operation. The solenoid is activated or deactivated as needed by the Engine Control Module (ECM).

While the variable intake air system solenoid is not operating, the vacuum signal to the intake manifold is interrupted. By the time the ECM determines that the solenoid should operate, a coil energizes the plunger, thus producing a vacuum feed signal to the valve actuator.

The P1801 OBDII fault code setting on Infiniti and Nissan vehicles is due to the fact that the signal received by the ECM from the variable intake air system solenoid 2 does not match the parameters set for proper operation.

Symptoms of fault code P1801

  • Check Engine light comes on.
  • The engine is unstable in operation.

Causes of OBD2 P1801

The DTC P1801 OBD2 is stored by one of the following factors:

  • Variable intake air system solenoid 2 wires or connectors may have common damage.
  • Solenoid 2 circuit connections may be faulty.
  • The variable intake air system solenoid 2 could be defective.

Possible solutions of the DTC code P1801

To troubleshoot the P1801 OBDII diagnostic code consider the following

  • Consult Technical Service Bulletins. The information contained in them is very useful.
  • Check that the electrical components of the variable intake air system solenoid 2 are in good condition for proper operation of the system. If corrosion, burning, or wear conditions are detected, make corrections.
  • Measure the supply circuit and ground circuit voltages for solenoid 2. If inconsistent voltages are found resulting in a short or open circuit, make the appropriate repairs.


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