Ok- thats all i needed to know.
The P0457 is the code for "Loose or Missing Fuel Cap" - although this may not be the main cause, seeing as the P0456 is set as well, it's a good idea to check it. Remove the fuel cap and check the o-ring on the underside for any cracks or chips missing from it. Make sure the cap seal tightly. Check the fuel filler neck for damaage or debris that may cuase the cap to not seal tightly.
The P0456 is a little tough to diagnose, and there is some visual inspections to perform first:
Perform a visual and physical inspection of the entire Evaporative Emission system.
Check for the following conditions:
- Holes or cracks
- Loose seal points
- Evidence of damaged components
- Incorrect routing of hoses and tubes
- Loose or missing Fuel Filler Cap
- Improper installation of the Fuel Fill Cap
- Damaged Locking tabs on Cap and/or fill tube
- Damaged seal points on Cap and/or fill tube
- Fuel cap gasket seal
If the above checks ok, the most common fail item with the P0456 is a faulty EVAP Purge Solenoid. Check the electrical connector for any loose or broken wires. Check, and then double-check the vacuum lines to and from this solenoid. If the visual inspection check ok, the solenoid is the best place to start. Another option is to have the EVAP system "smoked" - this is where a machine forces smoke throught the EVAP system, and the "small leak" will reveal itself. Most shops charge around $45-$65 for this service, but it's money well spent as chasing down an evap small leak "by eye" isn't very easy.
The duty cycle EVAP canister purge solenoid (1) is located in the engine compartment. It is attached to a tongue-type bracket near the brake power booster (3).