I have a hand held 2 way radio for the local logging roads and I was using it today and noticed whenever I would key the mic to talk my oil pressure gauge would drop right off and the “check gauges” alarm and light would come on. As soon as I would let off the mic the gauge would go back up to normal. Really had me confused/nervous the first couple times it happened before I put the 2 together. 

 

so what could be causing this to happen and why? 

Possibly a bad ground somewhere on the truck. 

8 hours ago, skyhigh4by said:

I have a hand held 2 way radio for the local logging roads

 

Handheld radio has no electrical connection to the truck. This is all RF (Radio Frequency) energy causing this. In the owners manual, there is a section about how caution should be used with strong RF signals in the vehicle. 

 

If you had an external antenna it might resolve this issue.  

Could be connected thu cigarette lighter socket for power. That's how my CB gets its power. Never any interference on the gauges though. All my grounds are tight and clean and does have an external antenna.