RepairPal is your advocate for car care advice and guidance

Q: Code PO455 has been detected. My check enging light came on. on 2004 GMC Envoy

What can I check for the cod PO455? I changed the gas cap, light went off and the came back on. Was told to put vasoline around the seal in gas cap.
Get a Repair Estimate
Guaranteed by certified locations nationwide. Learn more
RepairPal estimates are guaranteed at over 1,700 quality certified locations nationwide. Learn more
Assumming you purchased the gas cap from the dealer here is another posibilty.

Customer Concern: Evaporative (EVAP) DTC P0455
Tests/Procedures: 1. Start and run the engine.

2. Activate the purge solenoid using a scanner and check for vacuum through the solenoid.

3. Activate the vent solenoid and apply 2 inches of vacuum to the fuel tank and check Fuel Tank Pressure (FTP) sensor voltage. It should go up above 1.3-1.7 volts and hold steady.

4. Perform TSB #05-06-04-014A. It is possible that a fracture as small as 0.508 mm (0.020 in) may be found in the fuel tank filler neck, causing a DTC P0440, P0455 and/or P0442 to set. Due to the location above the liquid fuel level, this small fracture will not cause a visible fluid leak.
Potential Causes: Filler Neck
Fuel Tank Pressure (FTP) Sensor
Gas Cap
Purge Solenoid
Vent Control Solenoid
Wiring Connection

Diagnostic Codes: P0455
Potential Causes:Filler Neck,Fuel Tank Pressure,(FTP) Sensor,Gas Cap,Purge Solenoid,Vent Control Solenoid,Wiring Connection. There are numerous test that would need to be ran to pinpoint exact problem. Cheapest route would be to get a new gas cap from a GM dealer, aftermarket caps usually do not work and vasoline is a wives tale. There are numerous confirmed fixes:OEM Fuel Filler Cap,Fuel Filler Neck,EVAP Canister Vent Hose,Evaporative Emissions (EVAP) Canister Purge Solenoid/Valve,Fuel Tank,Vent Control Solenoid. As I said without performing proper test the only other option is to replace part by part, but I would definetly start with GM gas cap.
Didn't find what you were looking for?