Originally Posted by GM
Subject: Fuel Tank is Slow to Fill and/or DTC P0446
Models: 2005-2007 Chevrolet Cobalt
2007 Pontiac G5
2005-2006 Pontiac Pursuit (Canada Only)
2003-2007 Saturn Ion
This PI Supercedes To Include 2007 Model Year. Please Discard PIP3627.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
On rare occasions, the gas station fuel nozzle may shut off intermittently or prematurely while filling the fuel tank and/or the SES lamp may be illuminated due to a P0446 DTC. This condition may be caused by a partial restriction of the EVAP canister vent pipe, typically caused by insect nests in the pipe. Since a very sensitive measurement (Inches of H20) is used to monitor the EVAP system pressure/vacuum level, this pipe does not have to be 100% restricted for this concern to occur.
If the SI diagnostics do not isolate a cause for this concern, inspect the EVAP canister vent pipe for a partial restriction that may be caused by insect nests, etc. The EVAP pipe in question has one end attached to the EVAP canister (Item # 1 below) and the other end attached near the top of the filler neck. To determine if this is an issue, remove the pipe, hold a shop rag at one end of the pipe, apply shop air to the other end of the pipe, and determine if any debris is collected on the shop rag. If debris is present, this is most likely the root cause of the concern. Depending on how much debris is present, it may be necessary to use pressurized water to remove all of the debris.
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.