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Code P0456

3414 Views 1 Reply 2 Participants Last post by  wmburns
My inspection is due this month and although my car is running just fine the check engine light decided to pop on this morning, the day I was going to take her to get inspected of all days. I read other's suggestion to change out the gas cap and unfortunately it didn't due anything. Any suggestions as to how to go about investigating an Evap leak and a recommend next step would be greatly appreciated.
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It might be real handy to mention the model year of your Mustang. Why? The EVAP system is very different between a 96-98 and a 1999+.

Regardless of which Mustang you have for an older Mustang one of the 2nd places to look (after the gas cap), is the gas tank filler neck. There are two problem areas. The filler neck grommet and the filler neck itself rusting through. Especially if your filler neck has the plastic rock shield.

Finally, on some older model year Mustangs, an EVAP related DTC will not clear on it's own. The DTC code will have to be reset with an ODB2 reader or battery disconnect.

On newer Model year Mustangs, the DTC code will reset after a few successful drive cycles.

Soooo if you didn't reset the code, it's actually possible that the problem has been resolved but you just don't know it.
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