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.
Circuit Description
EVAP system includes fuel tank, fuel tank pressure sensor, EVAP pressure switching solenoid, fuel lines and hoses, vapor and purge lines, fuel cap, EVAP canister, and EVAP canister purge solenoid valve. Once every drive cycle, EVAP system will run a 25 to 40-second diagnostic where it monitors possible leaks at fuel tank pressure sensor, vent valve and canister purge valve.
This diagnostic has 5 phases and can set different DTC depending on which part of the diagnostic fails. If tank pressure is too slow reaching a certain value in the first phase, this DTC will set. It can also set in the third phase if tank pressure fails too slowly when vent and purge are both opened. This DTC indicates that the vent valve is either blocked open or closed.
DTC will set when:
- Vehicle speed is zero MPH.
- Engine at idle.
- Fuel system in closed loop.
- Battery voltage greater than 11 volts.
- Engine run time greater than 1.45 minutes.
- Altitude less than 9000 feet.
- Fuel level between 1.85-14.0 gallons.
- No TP, ECT, VSS, fuel tank pressure, O2S, idle control, purge valve, vent valve, battery voltage, misfire and EGR DTCs set.
When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. ECM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.
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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.
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