My check engine light just came on and and scanned for codes and got:
PO441
P0456
P0441 p
P0456 p

Anyone know what these codes mean and the best way to resolve the problem or part needed? I'm not a mechanic but I'm an engineer and usually repair my own vehicles. This is for a 2004 Mazda3 Hatchback. 2.3L Manual Trans. Thank you!

 

Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened.

Any of the following could also be the cause:

A small leak in any of the EVAP hoses or fuel tank hoses
A small leak in the purge valve or vent valve
The EVAP Canister may be leaking

Possible Solutions:

First, using a scan tool activate the vent solenoid, sealing the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the number will stay consistent. If is isn't, the pressure sensor will show that as well. If the system slowly leaks, use a smoke machine and watch for smoke exiting the system at any EVAP component. Any where there is smoke exiting the system, that is the faulty component. Do not pressurize the EVAP system with air pressure. Doing so can damage the purge and vent solenoids in the system.


A code P0441 could mean one or more of the following has happened:

Bad vacuum switch
Broken or damaged EVAP line or canister
Open in PCM purge command circuit
Open or short in Voltage feed circuit to Purge Solenoid
Faulty purge solenoid
Restriction in EVAP solenoid, line or canister
Corrosion or resistance in purge connector
Bad PCM

With a P0441 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

Repair damaged EVAP lines or canister
Repair open or short in voltage feed circuit to Purge Solenoid
Repair open in PCM purge command circuit
Replace purge Solenoid
Replace vacuum switch
Repair restriction in Evap line or canister or solenoid
Repair resistance in purge connector
Replace PCM

FROM: OBD-II Trouble Code: P0456 Evaporative Emissions System - Small leak detected

The 2 are obviously related. First do gas cap, then purge solenoid valve.

 

biggest issues are the fuel cap and the purge valve. the purge valves on the earlier 3,5,and 6's are junk. the fuel caps also stop sealing the evap system due to wear and poor design. i would replace both parts generally when its just the cap it wont set all 3 evap codes but the purge valve will.

 

This engine light seems that about powertrain in engine. Also this diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using engine intake manifold vacuum. ( P0456 Engine Trouble Code - P0456 OBD-II Diagnostic Powertrain (P) Trouble Code | EngineTroubleCode.com )