Error Code P1800 is defined as Variable Intake Air System Control Solenoid Valve Circuit.

This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as Nissan, Citroen/Peugeot, Ford, GM, Opel, and Toyota. Specification on the definition, troubleshooting, and repairs still vary from one make and model to another.


As the engine runs at low or medium speed, the power valve is fully closed. During this condition, the effective suction portion length is equal to the total length of the intake manifold collector’s suction ports, which includes the intake valve. This long suction port provides the increased air intake, resulting in improved efficiency of the suction as well as higher torque generation.

Both the surge tank and one-way valve are provided. When the engine is running at high speed, the PCM (powertrain control module, also known as ECM or Engine Control Module in other vehicle makes) sends the signal to the VIAS (Variable Intake Air System) control solenoid valve. The signal is then introduced by the intake manifold vacuum into the power valve actuator, which then opens the power valve to the two suction passages, along with the collector.

During this condition, the effective port length is equal to the length of the suction port provided independently for every cylinder. Shortened port length will result in improved engine output with reduced suction resistance under high speeds.

The VIAS control solenoid valve cuts the intake manifold vacuum signal for power valve control. It responds to On/Off single from the PCM. The vacuum signal from the intake manifold is cut when the solenoid is off. When the PCM sends On signal, the coil pulls the plunger down, feeding the vacuum signal to the power valve actuator. Too low or too high of a voltage signal will be sent to the PCM through the valve.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the system. Other symptoms include:

  • Sluggish engine

Possible Causes

There are a couple of possible causes for this error code, namely:

  • Defective VIAS control solenoid valve
  • Open or shorted VIAS control solenoid valve circuit harness
  • Poor electrical connection in VIAS control solenoid valve circuit

How to Check

VIAS solenoid is a dealer item only. This component is bolted right in front of the intake manifold. If it’s what is causing the problem, then it’s not expensive to replace. 1/10mm nuts are all that holds this thing in place.

As said earlier, this component controls the power valves inside the intake manifold. It turns the vacuum On/Off to the power valves. If this thing is not working as it should, the engine will feel sluggish. The engine control module controls this based on the inputs from the sensors. It works at times the car won’t have the power band and get up and go.

How to Fix

The common repairs for this error code include:

  • Replacement of VIAS control solenoid valve
  • Repair or replacement of open or shorted VIAS control solenoid valve circuit harness
  • Repair or replacement of open or shorted VIAS control solenoid electrical connection

If you hear some ratline sound even by just barely stepping on the gas pedal, that means there may be some loose screws in the power valves, which is what usually causes the rattling. This also would cause the error code as they wouldn’t be opening properly. If this is the case, it is best to have your vehicle checked by a certified technician, as he/she can listen and identify that noise.