What this code means

The PCM detected fuel vapor flow through the EVAP system when it should be sealed (non-purge condition). The PCM seals the system by commanding the Purge Solenoid OFF and the Vent Valve ON, then monitors fuel tank pressure for unexpected vacuum changes. A leaking purge solenoid valve is the most common cause.

Symptoms

• Check Engine Light
• Rough idle
• Fuel odor
• Decreased fuel efficiency
• Poor acceleration
• Difficulty starting when engine is hot

Common causes

• Defective EVAP purge control solenoid (most common)
• Defective charcoal canister
• Leaking vacuum lines in EVAP system
• Loose or damaged gas cap
• Clogged EVAP canister
• Overfilling fuel tank (damages charcoal canister on GM vehicles)

Diagnostic steps

1. Test EVAP purge solenoid for leakage
2. Inspect vacuum lines for cracks or disconnections
3. Check gas cap seal
4. Smoke test EVAP system
5. Test charcoal canister for saturation
6. Monitor fuel tank pressure sensor with scan tool

Repair notes

Replace EVAP purge control solenoid first (most common fix). GM charcoal canisters are susceptible to damage from fuel tank overfilling. If canister is saturated, replace it.

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