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 Control System Diagnostic Procedure
The enhanced Evaporative System Diagnostic is a precise series of eight operational subtests on the system. In some cases, the failure of only one subtest will end all evaporative system testing; however, in many cases, the on-board system will conduct a series of subtests before storing any DTCs.
The diagnostic codes associated with the system include DTC PO440, PO442, PO446, PO452, PO453, and PO144. Refer to FAULT ISOLATION article.
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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.