Ford Mustang Forum - View Single Post - Help with 2002 V6 Coupe & PO455 code
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post #4 of (permalink) Old 02-19-2011
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b1lk1's Avatar
Joined: Jul 2008
Location: Long way from home
Posts: 2,747
The EVAP system can be a downright pain in the a$$ to diagnose properly. The codes can be misleading and you gotta really do proper troubleshooting to get it nailed the first time. All manufacturers use different codes for different faults yet the OBD2 codes are standardized so one code can mean something else on a different car.

As for the gross leak code, as I said, most of the time it is because the vent solenoid is stuck or broken. Many times, it will still report correct voltages to the ECM/PCM so it will not cause the CEL. But, when the car does it's self diagnostic test on the EVAP system, it will not be able to pressurize the system so it reports a gross leak. A leaking gas cap almost never reports as a gross leak as well.

Technically, you REALLY need a bi-directional scanner and a smoke machine to work on the EVAP system. The scan tool can force the EVAP test and cycle the solenoids so you can in it down there if that is the problem. If everything works then you know you need the smoke machine and test for leaks. Also, even if the scan tool cannot force the solenoid to function you still gotta check the wiring to be sure there are no breaks in the wires to the solenoid.

I've been a mechanic for 20+ years and if there is one system that is really annoying to work on it is the EVAP.

1988 Mustang LX coupe will miss you greatly
traded for:
2004 Mazda 6s 5 door Sport w/5spd/3.0/RX8wheels/Kon/Eibach/and then some

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