Take to your nearest partshouse ( Kragen, Autozone) They will usually plug it in and tell you what is wrong for free
With a scan tool.
That requires a scan tool.
With an OBD2 scan tool.
There are pages of causes, you need to have it checked for codes.
Put the key in the ignition, and turn it from "off" to "run" (WITHOUT STARTING) Three times. The odometer screen should then start to read out the stored fault codes.
That is the check engine light. You will need to have the system checked for codes to know posssible causes.
With a scan tool.
There are pages and pages of codes for a 2005 ram. You need to have it checked for cades to know what is the cause.
Cylinder #7 Misfire
turn the key to on and then off 4 times. any codes will appear in the mileage box. If there are no codes, it will read p done. If there are codes it will show P??? and then P done.
Trouble code P0700 means: Automatic Transmission Control System Malfunction You need to check the TCM for codes
If the check engine light is or has illuminated, have it scanned for codes. They may help find the cause.