1995 Explorer Turns Over But Belt Doesn't Turn

[afrase]

My 1995 Explorer with a 4.0 V6 and 175K died while driving up a hill and all power was lost after hearing a clunk. Now the truck turns over but will not start. When the engine is turning over the serpentine belt does not turn with it. The belt is mounted correctly on all the pulleys but the Harmonic Balancer is not turning. I’m not sure about the crank shaft itself. I assume the engine is turning over since the noise doesn’t sound like a free spinning starter. I tried to listen and look into the oil fill neck while cranking the engine but could not perceive if the valves were moving due to a long filler neck. I've checked the engine for any codes that shed more light on the issue and there were two, OBD I codes 13 and 14. Both were retrieved with KOEO.
13 - Cannot control rpm during KOER Self-Test low rpm check.
14 - PIP Circuit failure.
I'm not sure what these codes point to considering the other symptoms? Hopefully someone has some ideas as to what could be the cause. I'm worried the engine has seen its last day?
What steps should I take next?

 

[1Aauto]

Welcome to the site

 

[buckwill]

id pull the last two plugs or at least one easiest clost to the firewall,, put a remote starter wire on it or have your wife turn it obver,, stick your finger in the hole,, se if you have compression on the back of the engine,,, not likely,, as any break in the crank will usually make it turn but who knows,, if it did break its most likely in the last main just at the flywheel but id say u have to pull the engine if the flexplate ot crank is broken,, buck take the belt off the bottom pulley,, try turning the engine, then rock it back and forth,, not much,,, feel what is happening, u will feel something, let us know buck