How do you know if the pcm is failed ? And how do you fix a pcm

The powertrain control module (PCM) almost never "fails". Modern day PCM's (in the last 20 or so years) are programmable modules that can be updated as needed, and don't get malfunction typically unless exposed to unwelcome moisture and corrosion or electrical surges from modifications. Simply put - I unilaterally doubt any PCM concerns until absolutely everything else is exhausted as a possible cause. If it's a "no crank" issue, it's even less likely to be PCM related. Your PCM controls engine performance - not starting system concerns. Check your engine's 12 volt battery first and make sure there is a fully charged battery capable of handling a load. Your check engine light could be malfunctioning because of low electrical voltage, or even a burned out bulb. Focus on the starting system. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops