Car just repaired, now check engine light is on

I have a 2008 Chevy Equinox, and recently I noticed a gas smell…I saw Chevy had a special policy to replace the fuel pump module, so I took it to the dealership hoping that would be the problem. Fortunately it was, and they replaced it for free. I got my car back Thursday afternoon, drove it Friday, and it sat yesterday without being driven. This morning I drove to the grocery store, and on the way home my check engine light came on. I have an ODBII scanner, so I plugged it in and got this code:

P0455: Evaporative Emission System Leak Detected (gross leak/no flow)

So I was wondering: (1) what is the cause and/or solution to this problem, and (2) is it possible the dealership caused this problem when they replaced my fuel pump module?

It seems awfully coincidental not to be related to the repair, since it is a fuel system problem, but I don’t know enough about cars to be sure…thanks for any help!

While it is possible that the repair itself is the proximate cause of this code popping up, it is also possible that the situation is just a coincidence.

The usual causes of this code are a loose gas cap, or damage to the evaporative emissions system itself. The damage could be the result of forcing more gas into the tank after the gas pump shuts off for the first time (which leads to a gasoline-soaked carbon canister), or it could be the result of a defective purge valve in the evap system, or it could be the result of a disconnected/broken evap hose.

If I was in your situation, I would first try removing and then re-tightening the gas cap.
If that doesn’t turn off the lit-up CEL (after going through several drive cycles), then a visit to the dealership is probably in order, so that they can check to see if an evap hose was disconnected or damaged when they did their work.

When they replaced the fuel pump module they had to drop the gas tank which requires disconnecting several fuel lines. This includes quick disconnect lines and clamped filler hoses. Most likely they didn’t tighten a filler hose clamp or didn’t seat a quick disconnect vent line properly. They may even have overlooked putting the gas cap back on.

The no-flow code usually means that an evap line (in my experience, often the one connected to the dump valve itself) is blocked or crimped, or the one end of the engine-connected side of it is laying loose. (That, by the way, would give you a fuel smell some of the time.) A quick visual check of the hose map for your vehicle vs what’s under the hood will tell you if there’s a line disconnected or misconnected; I’d start there.

I’ve seen this code pop up on a disconnected line for gross leak. Maybe the tank vent line was not reconnected correctly. Either way, return it to the dealer and have then recheck their work.

Thanks for all the information everyone - I’ll call the dealership tomorrow and see when I can get back in there.

crj123082 You have made a wise decision. It sounds like the dealership may have caused the current problem.