Solving P0455 on Your 2020 Chevrolet Silverado
A P0455 on your 2020 Silverado means the ECM detected a large EVAP leak—a breach of 0.040 inches or larger. Your T1-platform Silverado is out of GM's basic warranty but covered by the federal emissions warranty. The gas cap is overwhelmingly the most common cause.
What You'll Notice
- Check engine light with P0455
- Possible P0449 companion code
- Faint fuel odor near the rear
- Gas cap seal worn after 5+ years
- Failed emissions test
Suspects by Probability
- Gas Cap Seal (Very High Likelihood): Worn rubber seal after 5+ years. Replace for $10–$25.
- Vent Valve Solenoid (Medium Likelihood): GM's vent solenoid sticking open. $100–$200. Check for companion P0449.
- Purge Solenoid (Medium Likelihood): Stuck open or leaking internally. $80–$180.
- Vapor Line Crack (Low Likelihood): Hose under the truck bed cracked from road debris. $80–$200.
- Charcoal Canister (Low Likelihood): Saturated from overfilling. $200–$350.
Diagnostic Path
Replace the gas cap ($10–$25), clear the code, drive 2–3 cycles. If P0455 returns, get a smoke test. On Silverados, also check for P0449—if present, the vent valve solenoid is the cause.
Warranty Coverage
GM's basic warranty (3 years/36,000 miles) has expired. The federal emissions warranty (8 years/80,000 miles) covers EVAP through 2028. Contact your dealer for mileage verification.
Safe to Drive?
Yes. P0455 doesn't affect the Silverado's engine, transmission, towing, or 4x4.