Well, I dunno. The Soviet military refused to back the Communist Party in 1991; Churchill wrote that the German military was planning to overthrow Hitler in 1938 in what they thought was the likely scenario of his policies resulting in the UK and France entering into a war with Nazi Germany. So it all depends.

But did the communist party refuse to back the communist party? Because the PLA is part of the CCP. It's not a separate military. It's the armed wing of the Chinese Communist Party. Senior PLA officers are senior party members. The PLA, by design, owes its first loyalty not to the people, or the law, or the constitution, but to the CCP. Significant political education goes on, permanently, to keep it this way.

I'm not saying it's impossible, but it wouldn't be a military coup; it would be the CCP splitting and turning on itself.