No power at key

WHAT year/ model is your vehicle?

VERY first thing I'd do is yank the battery posts off and CLEAN them. CLEAN. Put them back on tight

If the problem still exists, FIND the problem using the "voltage drop" method.

Let's say you cleaned the battery terminals so now do this:

Turn on the headlights, verify "they are dim."

Put one probe of your meter DIRECTLY onto the BATTERY NEGATIVE POST and the other probe on the block. Should measure VERY little voltage, the less the better. Zero is perfect, anything over a TENTH (.1V) is way too much

Leave one probe on the battery negative post, transfer the other "stab" into clean metal up near the headlights onto the unibody metal. Once again, you are looking for a LOW or zero reading.

If that is OK, make sure the headlights are "still dim."

Now stab one probe DIRECTLY onto the battery POSITIVE POST, and the other on the large exposed stud on the starter relay. Once again, zero or maybe .1V, higher is bad

If that is OK, Find the terminal on your bulkhead terminal that is fed by the fused link off the starter relay stud. If that is OK, and the headlights are still dim, it PROBABLY is internal in the bulkhead connector. Time to go inside the car, if you can reach it, and probe this same feed terminal in the bulkhead connector INSIDE the car.

If that is bad, time to yank the connector apart. If good, try to get a clip lead onto the ammeter posts, one at a time. Once again, you are measuring from the battery POSITIVE POST to first one, then the other, ammeter posts.

If that is good (zero or very low drop) post back, we have harness problems