From what I've read, a used cluster will not work because they are "locked" to the original vehicle.
I'm 95% sure mine is the instrument cluster but there is still a chance it is something else.
Have you gotten your alternator checked out yet? That was my next move before I started messing w/ the instrument cluster

 

If you replace a cluster it has to be factory new/virgin and you will need to do a software sync with it(autologic or SDD), period.

dont waste your time and $ with used clusters.

 

Had similar issues a few years back with my 06 FFRR and was wracking my brains out trying to find the cause of it. After much research and consultations with the members of the RR forum, we narrowed it down to the electrical system. Since these rigs require extensive amounts of electrical power to run all the sensors, etc., any glitch in the electrical system will throw out a bunch of codes and gremlins so I focused my investigation with the electrical system starting with the battery. Lo and behold, I discovered a hairline crack on the positive side of the battery case that wreaked havoc with the system when the battery would flex due to vibration, movement etc. but would be fine when the vehicle would be standing still, running on smooth surface or just start after a few minutes rest.

 

Thank you for the reply VegasLR3. The battery is only a couple of weeks old. I have a CTEK charger coming in today so I can keep it plugged in for a few days and make sure it is 100% charged.
UPDATE: I've been tinkering every night to see if I can nail down what the issue is. List of things I've tried:
- Went through the wiring under the passenger side door sill. Found 2 pairs of wires that were spliced. One pair looked like it was still the factory splice (it was 2 black/red wires crimped to 2 black/red wires. No corrosion evident on the wires). The other pair was 2 green wires feeding into one green wire. This splice had heat shrink over it and I assume it is not the original splice. However, it looked looked like it would sealed up nicely and the wire inside showed no corrosion.
- Removed battery, unplugged the 3 harnesses that plug into the TCM. I really though I was onto something here, as 2 of the 3 plugs had some corrosion, as well as where they plug into the TCM. Cleaned everything with CRC Electrical Contact Cleaner. Let it dry overnight, reconnected. No difference.
- Been watching the voltage to my OBD connection while driving. It normally sits between 13.5-13.7. Sometimes, first crank in the morning it will be up around 13.9-14.1
All of this brings me back to the instrument panel... I've been able to workaround the "flashers of death", door locks engage, etc issue by doing the following: Turn the key to the on position, disconnect the instrument panel, then reconnect and it will allow me to crank. Obviously this throws a bunch of communication codes, but it is the only thing I can do when I need to force it to crank.
To reiterate, this is an intermittent issue. Yesterday, I had to force it to crank first thing in the morning. Drove to a buddy's and left it all day while we went fishing. Cranked fine after fishing and drove home. After an hour or so, needed to go to the store, it cranked right up again without issue. Later last night, went to run an errand, wouldn't start (flashers of death again).
Any additional advice/ideas are greatly appreciated!

 

The characteristics you described sounds similar to how a immobilizer works, I don't remember but do these rigs come with it from the factory?

 

I've considered the immobilizer feature causing the issue as well VegasLR3.
Just not real familiar with how it works. I only have one key, it unlocks and locks the doors remotely without fail. However, when I insert the key and turn it to position 1, sometimes it says "key inserted" on the instrument panel, and sometimes it doesn't. If it says "key inserted" the truck cranks with no issue.
One thing I'm not sure of is how the chip in the key works. Is it only needed for cranking, or is it constantly verifying the presence of the chip? The reason I ask, is sometimes the truck will crank fine, but once driving, it will do the "flashers of death", radio off, etc. When this happens, the motor does NOT shut off and the truck is 100% still driveable.

 

Ok, it seems a little clearer now. From what I understand, BTW any veteran LR enthusiast can correct me if I am mistaken, is that the chip in the key fob operates separately from the electrical system of the ignition. The chip constantly sends a signal, like the ones for digital AV equipment, that request identity information from the computer systems inside the dash which in turn sends identity signals back to the key fob. When all the signals match, it then activates an unlock code that will allow the electrical current from the ignition switch to pass to start the vehicle. This also allows all security measures to be disabled since the brain knows that it is the right key.

Now while the engine is running and the signal from the key fob is interrupted, the computer will think that the system has been compromised since the engine is still running, and will activate security measures like lights flashing and doors locking. The engine will stay running as long as the main electrical system that operates the ignition and fuel delivery system is active. This also explains why the issue happens intermittently. If the key fob has been dropped, which happens with mine regularly that is why I bought a rubber case for it to protect it on impact, the PCB inside the plastic case may have a hairline crack that could be causing the signal interruption.

I am not saying this is the cause but base on my experience with RF and digital signals in terms of security, I would look into this probability. I welcome the LR professionals in the group to weigh in on my theory.

 

I thought that might be the cause of my problems so I tried my spare key which is new and I still had the same issues. I'm waiting on a instrument cluster to show up and see if that fixes my problems.

 

Please let us know the results of the new instrument cluster WYRover! Hope it works for you.
I'm still thinking my issue is instrument cluster as well. For now, I just have it free-floating and when I get the flashers/no radio or a/c, I tinker with it until it starts working again.
This morning I had to coax it to start, but the rest of the day I had no issues cranking it or while driving. It seems during the day, when the truck has been sitting in the Florida heat, I don't have the issue like I do when I crank it first thing in the morning.

 

There was another thread recently that led to replacing the instrument cluster and I think he/she tackled that same question as to whether or not it needed to be reprogrammed and how to do it. Try doing a search.

I'm nervous about this happening to me in the future. I had one similar incident where everything died when I went to crank it and it wouldn't crank and I got HDC and Transmission Faults displayed. Left it for 5-10 minutes and it started back up with no drama. I also have a persistent instrument cluster communication fault in the IID tool along with two others I can't quite remember (maybe parking sensors and height control?). Seems like they lose communication while cranking which might point to a weak battery/alternator or maybe instrument cluster woes.

Definitely test the alternator and battery. A bad alternator can quickly kill a brand new battery. However, since it seems to start right up later, it might be something messing with the communication between modules (like the instrument cluster or maybe corroded wires from a leak somewhere). Any damp carpets after rain?