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Adventures with P0442 / P0455 small / gross evap leak

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Crossposted from my post on Chevytalk, figured it directly applies to any SS or Silverado in general, hope it's helpful:

Patient is a 2006 Silverado SS - Intimidator edition, about 90K miles on it. A little while back began getting the TIGHTEN FUEL CAP error on the driver display. Code check showed P0442 small evap leak; further driving resulted in P0455 gross evap leak. Began having trouble filling the tank as the pump would constantly click off even at the slowest setting.

When it was just P0442 first hope was just needing a gas cap, since the one I had was an aftermarket locking cap with a very cracked O-ring seal. Installed new AC Delco # GT225 (GM # 15763225) a little different from original, doesn't have a "line" style tether on it but surround-style, but it's OEM and works fine. Cleared code and it came back, not really a surprise.

Next up, ordered AC Delco # 214-2082 (GM # 19207763) revised canister purge valve assembly. There are 2 different part #'s depending on your year model of GMT800 truck so look it up before ordering. This is the revision where the filter is separate so it can be remote mounted.

Old purge valve/filter assembly removed. Take care removing the clip from the white plastic connector to the canister; fingernail or a small screwdriver to gently push the tabs loose and slide the clip out - you're re-using the white plastic piece, which requires carefully cutting the plastic hose off with a utility knife, small side cutters, etc. I also used needle nose to help peel the hose off.


Purchased 12' of 1/2" hose, need about 16" of it to attach new purge valve to the canister, the rest of it to remote mount the filter towards the front of the truck. This is enough for my 2006 extended cab with purge valve at rear of tank and my chosen place to mount the filter by the transmission; measure your own installation to be sure.


New purge valve in place and connected, and found it easier to feed the hose from the large hole in the frame ahead of the tank and push towards the rear, then route the rest along the frame above the fuel line clamps and ABS module bracket.


Mounted remote filter above transmission tailshaft housing, zip-tied to the transmission vent hose, not too tight so the hose doesn't get pinched.


Cleared codes using Torque Pro, BAFX Products bluetooth OBD2 adapter, and my trusty BlackBerry Passport SE. :)


Post-mortem on the old filter showed a little bit of dust, not a ton of it, so I'm hoping my canister is still good. Some driving when I return to work Friday should show whether the codes come back, if they do, I'll do the canister next.


Edited by someotherguy (see edit history)
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