Code 52 knock sensor

[Adam-Gt-]

When I bought my car it chewed big end bearing so I put a new engine in it

I noticed that the knock sensor wire had been cut and a random knock sensor had been put in and wires just twisted together !!

I got a knock sensor from my mate so I put that in

It's showing up code 52 but I'm not sure if it's the wiring or the sensor it's self how do I tell ?

Also is there a specific way of connecting two pieces of shielded cable together ?

Thanks Adam