Gasp! It's the "Gas Cap Code"!

Oh no, you just pulled a code P0422, evaporative purge small leak detected… Here goes the needle in the haystack syndrome.

So what do you do? Recommend a new gas cap and ship it? Well you could do that, but would that be in your or your customer's best interest? You might get lucky and fix some like that. However, that type of approach is a recheck waiting to happen. With very strong communication skills up front, you may get away with it with that customer that day, but what about when the car comes back? Then what? The car still has to be fixed. What's worse is that the customer will likely return on a busy day and mention in the lobby in front of other people how they had to come back.

That's not good publicity for your other customers to overhear, since they don't fully understand the reasons for that customer coming back. So, wouldn't it be better to have fixed the car on the first visit? Obviously, yes. So, let's cover basic evaporative emissions system theory and operation. Afterward, we will look at a couple of evaporative emissions system problems and diagnose them. Technically specific information found in this article will be based on Ford vehicles. However, much of this information also can be applied to other makes. Always consult your repair information resources for vehicle-specific information.

Theory and Operation
Due to the volatile nature of gasoline, vap...