Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Evaporative Emission (EVAP) Natural Vacuum Leak Detection (NVLD) Module: Notes
The NVLD module is located in the EVAP canister vent hose, under the vehicle. Battery voltage (VBAT) through an inline fuse (if equipped) is supplied to the NVLD module to allow EVAP system diagnostics to run after the ignition is turned OFF. The NVLD module electrical connector also incorporates a communication (NVLD) circuit and a ground (GND) circuit between the NVLD module and the PCM.
Internal to the NVLD module is a normally open vacuum switch (closes with vacuum), a normally closed vacuum relief valve (opens with excessive vacuum), a normally closed pressure relief valve (opens during refueling), an internal ambient air temperature sensor and a timer. The NVLD module completes a series of checks to confirm the integrity of the enhanced EVAP system components in the engine running state and the ignition OFF state. When the ignition is turned ON and the engine is running the NVLD module sends the information stored during the ignition OFF tests to the PCM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.