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.
EVAP monitor
The EVAP monitor's purpose is to check for EVAP leaks and EVAP VSV and CCV malfunctions. The monitor performs the check by first introducing the intake manifold's negative pressure (vacuum) to the EVAP system. Then, the monitor records change in the EVAP system's pressure levels. The monitor runs when the following conditions are met:
- The engine is in a state of cold soak. During cold soak, the ECT and IAT are nearly equal and both are within 4 to 35°C (40 to 90°F).
- The vehicle is stopped and the engine is idling, or the vehicle is being driven at a steady speed.
- The EVAP pressure is stabilized (fuel in fuel tank is not strong).
Refer to the table and illustration below for further details on the EVAP monitor processes.
| Order | Operation | Description |
|---|---|---|
| 1 | Fuel vapor measurement | EVAP VSV is turned OFF (closed) and EVAP pressure is measured. If EVAP pressure is not stable, EVAP monitor is canceled to prevent inaccurate monitor. |
| 2 | Vacuum introduction | EVAP VSV is turned ON (open) and CCV is turned ON (closed). As a result, intake manifold pressure (vacuum) is introduced to EVAP system. |
| 3 | EVAP leak check | EVAP VSV is turned OFF (closed) to seal EVAP system. EVAP pressure increase is measured for 5 seconds when EVAP pressure is -20 mmHg and -17 mmHg. If increase is large, ECM concludes EVAP system has leak. |
| 4 | Restore | CCV is turned OFF (open) to finish EVAP monitor. |
NO RELATED
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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.