2012 Camry P0456

Ahhhh... the dreaded evap system DTC P0456.... don't you just love those evaporative emission system codes? They don't affect the performance of the car, but they turn the check engine light on anyway, and they can be highly annoying. I haven't seen many problems with the 2012 Camrys at all since they were introduced, and today I got the first I've seen with an evaporative emission system very small leak code P0456. Of course the first place I checked was the gas cap, and to be honest, its hard to tell if these things are locked down correctly, even when they were delivered from the factory. Toyota, for one reason or another, has changed gas cap designs. Now, instead of mulitple audible clicks when locking down a gas cap by turning it clockwise, the cap only makes one click to indicate that it's tight. Well, even when these caps are working correctly, its hard to tell if they are tight enough because of the 'one click' type action. First, I just cleared the code and performed an evap self test with a scanner and re-tightned the gas cap. The code returned, so I knew the cap wasn't loose but I still suspected that there was something wrong with it. So, before I proceeded to more complex evaporative emsission system diagnostics, I put a new gas cap on the car as a hunch and performed another evap self test. This time the evap system self test passed, and I knew for sure that the old gas cap was bad. Unfortunately, it appears that diagnosing these newer gas caps is going to be a bit tougher than the old ones. The older style gas caps were pretty easy to diagnose most times: they either locked down or they didn't. I wish I could say that I had a more scientific method to diagnosing this problem, but sometimes all you have to fall back on is experience and an educated conclusion as to what the problem is, and then replace the part based on that conclusion. If you don't have a scanner to perform an evap self test, a code reader should be able to clear the code for you once you replace the gas cap. The car's ECU will automatically perform another evap system self test within a couple drive cylces. If the check engine light doesn't come back on within a few drive cycles, you'll know that you fixed the problem.