SES MIL Evap DTC - keywords emission engine evap evaporative fuel large leak p0446 p0442 pressure purge solenoid tank vacuum vent

This PI was superceded to remove the statement: please submit a product report per Steve Bunce BQM= Engineering has enough info. Please discard PIT4347B.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some owners may comment that the SES or MIL is illuminated and when checking for DTCs the ECM will have set an Evap DTC. While performing normal diagnostics it may be noticed there is excessive moisture/water/corrosion at the vent valve solenoid, vent valve pipes, and/or EVAP canister. The vent valve solenoid draws fresh air from near the top of the fuel filler pipe. In some situations, it is possible that water spray from the rear wheels may be drawn in though the vent valve pipe at the top of the fuel filler pipe.

GM engineering is aware of this concern and working on a permanent correction. At this time clean and/or replace the affected components to correct the concern.

This PI will be updated or a bulletin will be released when a fix becomes available

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.