Evap System Leak (ideas please?)
 

I've been getting P0442, P0442P and P0456P on my 2005 Camry 4cylinder standard since about December 2011. For some odd reason, lately P0456P stopped when scanning when the CEL comes on again after erasing the code.

There's no symptoms of any problem so I think it's likely to be some small leak in the evap. Looking at my gas cap, it's a little dirty, but I don't see any cracks or damage, and I always make sure to fasten it on tight.

Should I still buy a new gas cap as a 1st step of troubleshooting.

I have emission test coming up soon. Will my car pass the test after I erase the codes and take it in for test? Any advice?

(Actually this happened for 1st time like about 4 years ago when the car was under warranty. The dealer simply said that I didn't fasten on the fuel cap right, and erased the codes and sent me home. After about 4 years, same codes now that the warranty has expired....)

Codes are for an air leak in the fuel tank or EVAP system.

P0422, P0422P
Gas cap, bad, wrong cap, cap not fully tightened.
Small leak a fuel vapor hose or EVAP system

P0456
Gas cap ditto.
Small leak in EVAP or fuel tank hoses, purge or gas tank vent or EVAP canister leak.

Given the cap is a cheap and easy attempt to fix, might replace it.

Depending on the state your in the emission site may check the cap for leaks.

Once the codes are cleared the computer needs to run through a preset test cycle (time/MPH/etc) and fail two times before resetting the codes. This takes driving time. Just because the check light is off does not mean the problem is solved as the testing may not be complete.

Not sure if cleaning the codes will get the car through emissions. If the test taps into the ODBII system any pending codes can be read. Pending means a test failed once and is pending the second test. A decent code reader will read out pending codes. Pending codes may fail the test.

Resetting the codes will have the computer running a lot of tests, the emissions test station equipment can determine how many. The emissions like the car to have completed all its self checks even if nothing is wrong or a test has failed.

Your state may allow only so many incomplete test, perhaps 2. If more the car will fail.

Typically states have websites with their test procedures.


If changing the cap does not solve the problem someone, you or a mechanic, is going to need to check the system for leaks which means getting under the car.