EVAP Large Leak Detected - keywords P0455

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

If the vehicle exhibits a DTC P0455 perform the following.

Do not reprogram or replace the ECM. There is no ECM software or calibration issue that will cause this DTC to set.

1. Check for loose gas cap and check condition of the gas cap seal and gas cap threads. The threads are damaged during refueling at times causing a leak
2. Check to see if fuel tank is nearly full (indicating a recent trip to the gas station).
3. Check for leaks / disconnects between all EVAP system hoses using EVAP tester. EVAP test may need to be connected at underhood port in order to check for fuel cap leak.

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.