Ya don't listen to this guy ^ and just start wasting money replacing shit.... If the cel isn't turning off then it probably isn't the main relay... but you need to follow this check list to rule it out

techauto.awardspace.com/ignition.html#

The main relay will throw a faulty code if it's bad but like I said I don't think that's the problem here... after you go through that checklist and you rule out the main relay, follow up with the code it's giving you and replace the barometric sensor you will need to swap the ecu... this isn't a hard thing to understand, don't just go replacing random shit start where the ecu is telling you the problem is.