my engine light stays on. everything is new for parts and even dealer ship gas cap is new. what else could be the problem.
Until you find out the exact diagnostic trouble codes that have been stored by the car’s OBD system, nobody could possibly provide any specific repair advice.
Most auto parts stores (Advance, O’Reilly, AutoZone, possibly others…) will “read” the trouble codes for you w/o charge. Then you can come back to this thread, post the codes, and get some specific advice. The codes will be in a format similar to P0123.
Since you mention a gas cap, I assume you have one of the evaporative emission codes. They can be triggered by ANYTHING that lets air into the system. The system inluder the gas tank, filler neck gas cap, gas tank vent, purge valve, charcoal canister and all the metal and plastic tubing,fittings and clamps that are part of the vapor recovery system.
I had a leak it took me 4 years to find. Actually I looked for 4 years before I took it to my mechanic who found it. It was a crack in the metal plate that screws into the plastic gas tank that the fuel lines go through and that supports the weight of the fuel pump. The weight of the pump bouncing up and down
cracked the plate on my 2002 Town and Country. He showed me two plastic tanks where the rust on the metal threads of the plate had made hokes in the plastic tanks screw threads. Luckily he was able to get mine apart without ripping a hole in the threads so all I had to buy was the fuel lines and fixture.