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Ok guys so I have a problem that I believe is immobilizer/relay related but I can't seem to find any threads with anyone experiencing the same symptoms and I've checked off some of the remedies to those other problems.

First a little background:
-Car sat for 6 months, no issues with starting prior
-Old battery was dead, so I replaced it with a new one with the same group and specs as the previous one.

Now...

When the key is turned to the second position:
-No sign of the Green Key symbol at all. Doesn't even flash briefly and disappear.
-No sound from the Fuel Pump
-Clicking/Tapping noise coming from below the steering column
-Starter turns over fine, engine doesn't start

Given all the above, I'm getting the feeling that something to do with the anti-theft/immobilizer system is causing an issue and cutting off the fuel pump so the car won't start. I've had this problem with a previous generation civic but that ended up being a bad tumbler, and in that case the green key was indicating the problem being with the immobilizer. In this instance, I'm getting no key symbol at all which leads me to believe it's the immobilizer but a different issue.

Checked all the fuses and they are all showing continuity. Haven't tried relays yet as I'm not 100% on how to use a multimeter to test those.

 
Rep Power: 224

I'm assuming you posted this in the correct section even though your username suggest you own a 7th gen. Check fuse 2 (15 amp) in the under-dash fuse box as well as fuse 23 (10 amp) in the under-hood fuse box.

 
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Doh! Didn't realize I forgot to identify the car. It's a 2007 Civic LX. The username is from one of my previous Civs.

Anyway, after spending some hours pulling my hair out over this, I stumbled upon this video:
Tried using a jumper wire in pins 4 and 5 of the diagnostic plug in to verify if I was having a grounding issue and the car started right up. The missing bolt he points out in the video ended up being my culprit. I had forgotten that a few months ago a friend dropped a socket that got wedged under the harness and he took those bolts out to be able to free the socket and must not have put them back in. I put the bolts in and the car is starting up with no issues without the jumper in place.

 
Rep Power: 224

Nice find! That's for sharing your solution