Ping is a sound similar to having metallic ballbearings in a tin cup, you hear it when the car is accelerating hard.
You shouldnt hear it at idle, my car has had this issue since new a 2009 Lux, dealer has done all the neccassry
required fixes.. I now only use Caltex 98 RON and this has rectified the problem 98 % I no longer worry about it.
If you have to have your head removed to get to the knock sensor you should be asking how much will this cost you....
My car has 45,000kms and love driving it pity the Japs didnt round the kilowatts to 150
Anyhow this car works a treat when you give it a good flog every now and then..
The mumbo begins at 4000rpm