On the 2006 GMC Envoy, the P0455 is a very general code that simply states there is a large leak in the EVAP (emissions control/recovery) System. First place to start here is with the fuel cap. Check the underside of the fuel cap for any cracks or signs of defects that may keep the cap from sealing correctly. If there are any doubts about the inspection of the cap, replace it. Keep in mind, you will need a cap that meets OE Specs. Those “universal” or “locking” fuel caps sold at after market parts stores do not meet OE specs. They will not seal the system correctly. Check the top of the fuel filler neck for any signs of damage or debris. Check under the vehicle, around the rear areas of the vehicle, looking for any vacuum lines that have dry-rot cracks, holes or loose/missing connections. If these all check out, then the next course of action is to have the EVAP System “smoked”. This is where a machines forces smoke through the system and any leaks can then be more easily found and repaired. If the smoke test proves no leaks, then individual items in the EVAP System will need to be tested. Very commonly on GM vehicles, a faulty Fuel Tank Pressure Sensor can set this code as well.
Does your vehicle have a similar problem? Get connected to a Live Q&A session with a certified Auto Mechanic and get your answers on this problem now!
If this article was helpful, leave a rating: