Currently in every state in the United States it is now acknowledge that the at-fault party is liable for the Diminished Value of a vehicle they have damaged.
Technically the at-fault party is liable, not the insurance company. But the insurance company, through the purchased insurance policy, is obligated to defend and pay damages of the insured. Each state has different laws about claim limits, and how long you have to file a claim, but if you have been in an accident that resulted in significant damage you most likely have a Diminished Value claim.
What if the at-fault insurance company denies your claim? What was the basis for their denial? It