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Discussion Starter #1
Alright, so I've done a bunch of searches (on here, on google, etc) where people have done this, and had similar issues, but I could not find anything.

What happened? -
I went to start my 2005 IS300 that had been sitting for a while, and the battery was dead. I was frustrated and in a rush, and managed to reverse the polarity of the terminals on my IS300. In my defense, whoever had the car before me, put new terminals on the car, and reversed them (the negative terminal is painted red) and in my haste, I hooked them up wrong.

What's the issue? -
When I realized what I did and swapped to the correct terminals, the car alarm started going off. I got the alarm turned off, disconnected the battery, and checked and replaced the fuses in both the driver and passenger side, and inside the engine bay fuse box. I replaced about 5 fuses in total (I forget which ones), and the rest checked good. I hooked the battery back up and charged it, the car started right up. I have some lingering issues however. My gauge cluster does not work(if I rev the engine up a bit, I can see a faint glow of a light trying to come on) other than that, no lights or needle movement, No radio, No clock, No power windows, No power locks, No seat warmers, No power sunroof, no power on my rear-view mirror, I believe my OBDII connection port is inoperable as well(I have an OBDII scanner that connects to my phone via blue-tooth, and my phone could not find the scanner when connected to my car). My power seats work, dome light works, as well as the horn, and I believe the headlights are working properly. I do not have access to the car right now, as I'm away at school. I'll be able to in a week or two. I just wanted to see if you guys could give me some suggestions on things I can check when I get back home to my car, relays? ECM? anything else?
 

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I imagine the OBD II reading module is toast, but the ECUs OBD II interface is fine (though of course I could just be entirely wrong).

Hooking up a battery in reverse is probably a common thing to protect against, so I'm hopeful you haven't burnt up any electronic modules (especially as the engine management seems to be operating fine as you say). That also makes me think it may be a common diagnostic issue with a procedure to resolve it detailed in the service manual; that'd be worth a check.

I would continue to check fuses/relays/modules related to those components that aren't working properly. It's possible that the interior dimming modules (I assume there is such a thing) need replaced, which would explain your "weak" lighting issue.

Just how long was the battery connected in reverse for? Did you turn on the accessories or ignition with it connected like that?
 

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Discussion Starter #3
Thanks for the reply.

The reading module was purchased after this happened, to resolve an o2 sensor wiring issue in my jeep. It has been used on a few different vehicles successfully after it failed to read in the car. This happened about a week ago, I tried figuring it out on my own for a while. As I recall, it was hooked up for maybe a minute tops, and I cannot remember if I turned the key in the car or not. I kinda entered a panic mode when I realized what I did. When I get back in town, I will check my manual for any procedures that might be in there.
 

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Discussion Starter #5
Today is my first chance to take a look at the car since posting this. I will be going through my manual and checking everything over again, and will post back when/if I find anything.
 

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Discussion Starter #6
Update: found that my 120a ALT fuse was blown. This could be my issue. Heading to AutoZone for a replacement fuse and will let you know how it turns out.
 

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Discussion Starter #7
That fuse was the culprit. All seems to be working normally now. Was hard to see that it was blown, so I missed it on my first walk-through of the fuses.
 

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Good to hear. I would imagine that in this day and age a car gotta have some sort of protection like this.
 
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