This happened to me too. The emissions test broke the diaphragm in the gas cap. Bought a new gas cap and it fixed everything.
The light is one because there is a problem with the emissions system. Once the problem is corrected the service tech will reset the light.
the vehicle has to be put on a computer to get the code. it could be emissions, but the computer will tell you what part of the system is failing, such as the oxygen senser.
The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to a parts store or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.
The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to a parts store or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.
The 2015 GMC Yukon has a V8 engine.
The 2004 GMC Yukon has a V8 engine.
The 2001 GMC Yukon has a V8 engine.
The 2008 GMC Yukon has a V8 engine.
The 2010 GMC Yukon has a V8 engine.
The 2006 GMC Yukon has a V8 engine.
The 2005 GMC Yukon has a V8 engine.
The 2009 GMC Yukon has a V8 engine.