Tapping engine when hot

I Belive that I have two problems or more. When the rover is cold the engine is runs quietly but after it warms up there is a tapping noise. The engine is not overheating so the temp guage says. I only take the rover on short trips about 5 miles to work with no problem, but I went into town and I herd the tapping. The temp guage was still normal temp, I turned on the heater on high seemed normal temp,

When the engine idles in drive my oil light comes on I put it into netural and the light goes away.

I also just got a 48 code, witch is the stepper motor and Idel control. I tried to clear it but it came back.

Any info would help, should I get a real temp and oil pressure guage what brand would you recomend, should I change my oil pump, stepper motor
anyway thanks for the help last time, Rockon

Rocker arms?

Man, wish I had joined this forum sooner.
The oil you are using is to thin. My guess is that you are using a 5w-30, which is fine for the winter time in the Mid West, East Coast, etc. but not for Southern California for example.
When there is a load on the engine it idles at a lower speed.
No load idle speed is 600-700 rpm, with a load it will be lower by as much as 100-150 rpm.
A slower engine speed will mean the oil pump is pumping slower which relates to lower oil PSI.
Oil thins as it gets hot, the hotter it is the thinner it gets.
I use 15w-40 in my truck in the summer and 5w-40 in the winter.
Switch to a thicker oil and if that does nto help then you need to check your oil pressure.
But I am willing to bet that the thicker oil will cure your problem.