2018 GMC Sierra P0455: Large EVAP Leak Repair

Solving P0455 on Your 2018 GMC Sierra

P0455 on your 2018 Sierra (K2XX) means a large EVAP leak. At 6+ years, the vent valve solenoid and gas cap are prime suspects. Check for P0449 too.

Symptoms

• Check engine light on
• P0455 and possibly P0449
• Fuel smell near rear
• Emissions test failure

Causes Ranked

1. Gas Cap Seal (Very High Likelihood): 6+ years of wear. $10–$25.
2. Vent Valve Solenoid (High Likelihood): Very common at this age on GM trucks. $100–$220 installed.
3. Purge Solenoid (Medium Likelihood): Worn. $110–$240 installed.
4. Vapor Lines (Low-Medium Likelihood): Age/truck use damage. $80–$220.
5. Charcoal Canister (Low Likelihood): Saturated. $180–$380 installed.

DIY Approach

Gas cap: easy. Vent valve solenoid: easy DIY near the charcoal canister. 30 minutes with basic tools. The purge solenoid is on the engine. Both are affordable GM parts.

Warranty

Basic warranty expired. Federal emissions (8yr/80k) covers EVAP through 2026—last chance.

Safe to Drive?

Yes. P0455 is vapor only.

Frequently Asked Questions