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P1800 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P1800 is an OBD-II Code that refers to Variable Intake Air System Control Solenoid Valve Circuit

Meaning

A P1800 code is a manufacturer specific diagnostic trouble code related to Nissan, Citroen/Peugeot, Ford, GM, Opel, and Toyota vehicles that occurs when the PCM/ECM detects a problem with the circuit that controls the Variable Intake Air System Control Solenoid Valve. The control solenoid valve of the VIAS cuts the intake manifold vacuum signal for power valve control. 

A signal is sent to the driver’s control unit, which turns on or off the power. When the solenoid is off, the vacuum signal from the intake manifold is terminated. When the PCM sends an On signal, the plunger is drawn down by the coil and delivered to the power valve actuator via the vacuum signal.

The P1800 code will be set when the signal from the PCM to the Variable Intake Air System Control Solenoid Valve is not within normal operating parameters.

Causes

Common causes for this code include:

  • Malfunctioned VIAS control solenoid valve
  • VIAS control solenoid valve circuit harness is open or shorted 
  • Bad electrical connection in VIAS control solenoid valve circuit

Symptoms

The symptoms of a P1800 code are:

Diagnosis

To diagnose a P1800 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the VIAS control solenoid valve and circuit for any issues.
  3. Check the electrical connection of the VIAS control solenoid valve for any corrosion or damage.
  4. Test the resistance of the coil in the VIAS control solenoid valve.
  5. Compare the results to manufacturer’s specifications.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1800 code:

  • Not thoroughly inspecting all the wiring and connectors for damage.
  • Not checking the VIAS control solenoid valve for proper operation.
  • Not clearing the codes after repairs have been made to see if the code returns.

How serious is this?

A P1800 code is usually not a serious problem, but it can lead to engine performance issues if it is not repaired in a timely manner.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Replacement of VIAS control solenoid valve
  • The harness of a VIAS control solenoid valve circuit is replaced or repaired if it’s open or shorted.
  • Repair or replacement of an open or shorted VAL control solenoid electrical connection

Related codes

A P1800 is related to and may be accompanied by the following codes:

P1700 – Variable Intake Air System Solenoid Circuit

P1801 – Variable Intake Air System Pressure Sensor Circuit Low

P1802 – Variable Intake Air System Pressure Sensor Circuit High

Conclusion

In conclusion, the P1800 code is a diagnostic trouble code that refers to a problem with the Variable Intake Air System Control Solenoid Valve Circuit. The most common causes for this code are a malfunctioned VIAS control solenoid valve, a VIAS control solenoid valve circuit that is open or shorted, or a bad electrical connection in the VIAS control solenoid valve circuit. The symptoms of this code are an illuminated Check Engine Light and bad engine performance. To properly diagnose and fix this code, a technician would scan for codes in the ECM, visually inspect the VIAS control solenoid valve and circuit, check the electrical connection of the VIAS control solenoid valve, test the resistance of the coil in the VIAS control solenoid valve, and compare the results to manufacturer’s specifications.