My father drives a 1999 3500 drw that he tows a 40' fiver with. He's complaining of a surging condition.

I'm told that when he disconnects the battery it "resets" it and the surging stops for a week or so then the surging starts again.

My first thought was a pump, but the fact that disconnecting the battery fixes it for a short while confuses me.

Any ideas?

 

Codes??

 

I will ask him what codes are being set, I forgot.