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Hi, the first thing I would do is remove the starter relay and jump from terminal 30 to 87 in the relay connector to see if the starter operates. You might just have a bad starter. If the starter works when you jump the relay you might have a bad starter relay. The relay is located in the module box under the hood on the passenger side. I've attached a picture below. Let me know what you find.
Okay. Let me know what you find.
First I would make sure that your battery is good. It sounds like it could be borderline. If the starter still will not operate with a good battery and the jumper in place you will need to replace the starter.
You have some strange electrical things going on with the key and the gauges. That's why I would make sure the battery is good. Connect a set of jumpers from another car to be sure.
Jumping the relay is a direct connection to the starter. You should make sure that the jumper is a good jumper and is making connection in the slots. You should also make sure that there is 12V at one of the two terminals you are jumping. If you have 12V at one of the terminals and nothing happens when you jump to the other terminal that would indicate a bad starter.
It's not good if you can't turn the key. That could be a problem with the key or with the lock or switch that you already replaced. Try disconnecting both battery cables and jumping the two cable ends together for 5 minutes then reconnect them to the battery and see if the key will turn. I'm going to be out of touch until later this evening. Let me know how you make out and I will reply back asap.
The lock, switch and ECU all need to be from the same vehicle. I'd perform the last tests I gave you so we can see if you are getting 12V to the starter. I wouldn't worry about the key not turning at the moment. Let's first find out if the starter is bad then we will deal with the switch.