Will leaving gas cap off cause engine light to come on

SOURCE: The check engine light just

yes it most certainly will. people dont know this. but its very true. have a nice day

SOURCE: replaced gas cap engine light came back on

Aftermarket gas caps are not always good. Suggest a cap from dealership. These evap systems are equipped with a purge valve and a vent valve. The purge valve is located at the front of the intake manifold(top). The vent valve is located under the vehicle just above the front of the spare tire. The most common failure is the vent valve due to exposure to road debris and water. Check with your dealer for design revisions to the replacment valve and vent hose routing to keep contaminants out of the new valve.

SOURCE: I have been getting a check gas cap notification on my 2006 chevrolet uplander. i check it and it seems to be fine. Then i get a check engine light. Can the gas cap cause a check engine light to come

Yes. Any leak in the evap system can cause a check engine light. A smoke machine can be used to isolate the leak. You most likely have a purge solenoid or vent solenoid leaking when commanded closed. The most common being the vent solenoid, located under the vehicle