Knock Sesnor Code - Honda CRV 2002

Hi experts,

I need your help. I have bought Honda CRV 2002 5 days ago. The owner said that everything is fine. When I took test drive, the car was heated up as it has been driven for some time and there was no check engine light on.

The check engine light is coming on and off. I took it to mechanic when there was no check engine light and he said it is knock sensor code. He cleared the code and told me to come back to him when the light is on. The driving is fine and the car runs smooth even if the sensor shows up.


Details:

When I start my car in the morning, after driving around 0.5 km, the check engine light comes up and stays on until I reach office after driving around 10 km (Car is heated up). If I restart the car immediately, no engine light. If I keep driving, the light does not come back. However, if it is parked for 2 hours, it cools down and if I drive then, the light again appears after driving 0.5 km.


I have done minor service recently with oil change.

What could be the reason from the following? Please advise.

Faulty knock sesnor?

Low octane fuel?

or something else

Regards,
Zubair