Faulty vacuum cut valve bypass valve (solenoid) itself; Damaged or disconnected electrical connector at the valve; Open or shorted wire in the valve circuit (including chafed harness); Corroded or loose terminals in the connector or at the ECM; Failed ECM driver for the valve circuit (less common); Vacuum hose leaks or blockages affecting valve operation (indirectly causing circuit codes)

DTC codes / Nissan codes / P1490

P1490 · NissanVacuum Cut Valve Bypass Valve Circuit

Q: What does code P1490 mean?

Vacuum Cut Valve Bypass Valve Circuit. P1490 on Nissan vehicles indicates that the engine control module (ECM) has detected an electrical fault in the vacuum cut valve bypass valve circuit, which is part of the evaporative emission (EVAP) control system. The ECM monitors the circuit for expected voltage or current and sets the code when the signal is out of range, often due to an open, short, or excessive resistance in the valve or its wiring.

P1490 on Nissan vehicles indicates that the engine control module (ECM) has detected an electrical fault in the vacuum cut valve bypass valve circuit, which is part of the evaporative emission (EVAP) control system. The ECM monitors the circuit for expected voltage or current and sets the code when the signal is out of range, often due to an open, short, or excessive resistance in the valve or its wiring.

SystemPowertrain

Code typeNissan specific

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light (malfunction indicator lamp) with no other noticeable symptoms
A slight fuel odor may be present if the valve fails to seal properly
Rough idle or hesitation in some cases if the valve affects vacuum routing
Failed emissions inspection due to the stored code
In rare instances, a hissing sound from the engine bay if a vacuum line is disconnected

Common causes, most likely first

Faulty vacuum cut valve bypass valve (solenoid) itself
Damaged or disconnected electrical connector at the valve
Open or shorted wire in the valve circuit (including chafed harness)
Corroded or loose terminals in the connector or at the ECM
Failed ECM driver for the valve circuit (less common)
Vacuum hose leaks or blockages affecting valve operation (indirectly causing circuit codes)

How to diagnose and fix it

Verify the code with a scan tool and check for any related EVAP or vacuum codes.
Inspect the vacuum cut valve bypass valve connector and wiring for damage, corrosion, or looseness.
Test the valve's resistance with a multimeter and compare to the manufacturer's specification.
Check for continuity and shorts in the wiring between the valve and the ECM.
Apply vacuum to the valve and verify it holds and releases properly when powered.
If the valve fails electrical or vacuum tests, replace it and clear the code.
If wiring and valve are good, diagnose the ECM driver circuit or replace the ECM as a last resort.

Don't overlook the simple connector first

A loose or corroded connector at the bypass valve is a frequent cause of P1490, so always inspect and clean terminals before condemning the valve.
The code can be set by a valve that tests fine electrically but has a stuck mechanical plunger, so a vacuum test is essential.
Nissan EVAP systems often use a pressure sensor that can trigger this code indirectly if vacuum lines are misrouted after repairs.
Replacing the valve without clearing the code and performing a drive cycle may lead to a false return of the code if the ECM hasn't re-learned.
Some aftermarket valves have different resistance values and can cause repeat codes; always verify against the factory specification.

Can I keep driving with P1490?

The vehicle is generally safe to drive with P1490 because it primarily affects emissions and not engine performance, but avoid long trips until repaired and address it promptly to prevent EVAP system complications.

Tools that help

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Guidance is general and written for Nissan vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.