How can i make sure the gas cap is the problem

Question

Have two codes pP0442and pP0456put new gas cap on and still get the codes but cap seams to be not locking

Answer 1

Hi there,

Really the only way to know is with a smoke test. This is a very small leak in the system someplace. If you aren't sure the gas cap is locking or if you didn't use a factory replacement from the dealer, then it's possible it is the problem. Again, a smoke test on the evap system is the only way to locate the small leak. The gas cap can be tested as well.