Persistent P0455 and P0456 Check Engine Light

A few weeks back I received both the P0455 'Evap System Large Leak' and P0456 'Evap System Small Leak'. I tightened my gas cap, cleared the alarm, and it came back a couple days later. I inspected the seal on the cap, and the rubber felt a little bit hardened, but nothing too concerning. Since I'm not aware of how small a leak will set this alarm off, I decided to replace the gas cap, as I read this was the most likely cause of the alarm.

For some reason a new Mazda gas cap costs $50! Regardless, I bought a new one and replaced the old one. Cleared the alarm, and two days later it's back again.

Before I go on a replacement spree, I was wondering if anyone has an opinion for the next likely cause of the leak? What does it mean that I am getting BOTH the P0455 and P0456? Looking back, if it was really only a small leak from the gas cap, should I have just gotten the small leak alarm, and not the large? Is the fact that I'm getting both alarms a clue as to what may be causing it?

I'm new to performing my own maintenance on my car, so if you could explain any troubleshooting in very simple terms, that would be appreciated. This alarm doesn't appear to be a major concern for the performance of my car, but it's still annoying having the CEL on all the time.

My car is a 2013 CX-5 Sport AWD. Thanks for your help.

Maybe get a diagram of the evap system under "engine" from the service manual on this forum and see wherever there's a rubber part and check that connection. I once had a cracked charcoal canister set off an annoying code.

straight from service manual
p0455
determination condition

P0455:00
l Hole of 0.09 in (2.25 mm) or more in evaporative gas passage

possible causes
l Missing or loose fuel filler cap
l Fuel filler cap malfunction
l Fuel tank pressure sensor malfunction
l CV solenoid valve malfunction
l Purge solenoid valve malfunction
l Evaporative gas passage malfunction
n Improper connection of evaporative hose
n Evaporative hose damaged
l Charcoal canister malfunction
l Catch tank malfunction
l Evaporative gas hose passage restriction
n Pressure control valve malfunction
l Fuel pump unit loose
l Fuel tank malfunction
l PCM malfunction

determination
P0456:00
l Hole of 0.02 in (0.5 mm) or more in evaporative gas passage

detection condition: (also precludes other codes possible causes if the code is thrown, which I bolded)
P0442:00, P0455:00
l Period ignition is switched off before engine starts: 120 min or more
l Engine coolant temperature at engine start: 2—43 C {36—109 F}*1
l Time elapsed from engine start: 6—90 min
l Fuel level in fuel tank: 10—90 %*1
l Desired ambient air temperature: 4.4—43.3 C {40—109 F}*1
l Barometric pressure: 72.23 kPa {0.7365 kgf/cm2, 10.48 psi} or more*1
l Charging efficiency: 3—65 %*1
l Vehicle speed: 64—144 km/h {40.0—89.4 mph}*1
P0456:00
l Engine coolant temperature at engine start: 2—43 C {36—109 F}*1
l Intake air temperature at engine start: 7 C {13 F} or more higher than engine coolant temperature at engine
start*1
l Time elapsed from engine start: 15—90 min
l Fuel level in fuel tank: 10—90 %*1
l Desired ambient air temperature: 5—37 C {41—98 F}*1
l Barometric pressure: 72.35 kPa {0.7378 kgf/cm2, 10.49 psi} or more*1
l Battery voltage: above 10 V*1
l The following DTCs are not detected:
n Fuel tank pressure sensor: P0451:00, P0452:00, P0453:00
n Purge solenoid valve: P0443:00
n CV solenoid valve: P0446:00
n EVAP monitor: P0442:00, P0455:00, P0457:00, P144A:00, P1450:00
n Fuel gauge sender unit: P0460:00, P0461:00, P0462:00, P0463:00
l *1: Value can be verified by displaying PIDs using M-MDS

it also goes into more detail and explanation. in paragraph form. pm me an email if you want a copy.

Aren't these covered by the factory warranty for 5/60 for powertrain and emissions?

2013 probably out of warranty although certain emissions items are covered for 10 years or something gotta look at the warranty booklet.

The emission items that are covered under the Federal 8/80 warranty are more often than not limited to the Cat converter and the ECU. I'm sure some one here will find something a little more specific. On the simpler side, OP's car is over 4 years old, not uncommon for rubber hose connections to start getting brittle and causing leak problems.

https://www.ncconsumer.org/news-articles/federal-extended-emissions-warranty.html

http://www.consumerreports.org/cro/...000-on-emissions-repair-for-his-bmw/index.htm