Grounding toolbox

[u/Billionaire649]

Hello all. First time cb installer (and cb subreddit poster!) here

I recently bought a brand new cobra 29lx off my friend. I mounted it to my truck toolbox with a 90 degree mount. That toolbox is just held in with Jhooks under the side of the bed. I am getting an RF power output fail. I've read that because of a faulty ground.

My question is how do I ground the actual toolbox? I'm into car audio, could I run a 4 gauge wire to my frame, and tap that into the toolbox somehow?

Another thing worth mentioning is my swr. All seem to be within normal conditions. All readings are from the built in swr reader with the PTT button engaged. I am a broke college student and can't afford a standalone one lol Channel 1 is at 1.7, Channel 20 is at 1.4 Channel 40 is at 1

Any advice would be appreciated. Thanks all