GTSMark

I have 2012 Porsche 911 GTS with 23,000 miles. Had the oil changed at an Indy shop and a few drives later got a CEL, so took it back in case it was related to that servicing. They pulled the CEL code as P0456 Evaporative Emissions System Leak(small leak-exceeds limit value). They said the gas cap was on wrong(I did not believe that!), reset the CEL and did a system test. All was OK for about 5 short trips and the CEL came on again. Back to Indy shop and the code was the same. They did a "smoke test" to try and find a leak and then diagnosed the problem as a faulty DMTL leak detection module. This part was replaced, the system checked, CEL cleared and hoped the problem was solved. About 5 drives later the CEL came on again and took it to the Indy shop. Same code. Gas Cap was replaced and code cleared along with system test passed. Drove the car multiple times including a 550 trip, with multiple fuel fill ups. CEL came on yet again, so went to AutoZone(since travelling). They pulled the same CEL code. They guy was nice enough to lend me a code scanner and I cleared the CEL(this was just a few hours from when it came on). Have now driven 550 miles home without the CEL coming on again, but expect it to come on again. The CEL comes on when the car starts(both cold and warm) and so far has not come on when the car is in use. I live in VA, which does Emissions and Safety Inspections, so a CEL will be a fail. I don't know whether the inspector uses a scanner as part of the inspection--so that the CEL code history can be read and if that is a failure. Any suggestions on what to do next to fix this intermittent problem and pass VA inspection are much appreciated. Thanks.

911-997

If you have a CEL, you will not pass emission tests in VA. Been there, done that!

ChicagoSpeed996

Sounds like what is happening is the CEL is being reset and so is the emission drive cycle. As you start driving, going through the drive cycle, the emissions system is doing the EVAP check. The EVAP check is looking for leaks in the emissions system. The EVAP test is done in between 3/4 and 1/4 tanks of fuel to do anomalies in the other ranges of fill. Sounds like you may have an evap issue. They should be able to smoke the emissions evap system and look for leaks. Check the tubes going to the intake manifold near the throttle body in case they bumped them loose during the oil change.

DC911S

Get the evap system checked. There is a check valve and a canister and hones.

nivlak

I had the same P0456 code appear and needed to get my car Maryland emission tested. I cleared the code with my Durametric the day before I took it in. In their testing they could see that the codes had been reset recently so asked that I drive the car around and come back in two weeks. I went back in 2 weeks and the CEL had not reappeared yet. The car passed emissions inspection and two days later the CEL came back on. Glad it passed but like everyone else it would be great to know the source of the problem. Im new to using the Durametric tool. It specifies a part number 997.618.655.06 but i cant seem to find that part anywhere. Is anyone familiar with this part? Thanks!

GTSMark

Update to my OP. I have not had the CEL come on again and have driven about 2000 miles since April when I cleared the CEL. My emissions was still valid when I renewed the VA registration, so I did not have to have the emissions check this time in July. I don't have an OBD to check whether the drive cycle is completed, suspect it has. So, just waiting for it to happen again.