I hope this helps someone. I have a 2000 Winnebago with an F53 chassis. I replaced the engine battery a short time ago and when I took her on a short trip she threw a PCM trouble code P0720. She also started stalling whenever I backed out of my driveway (very uneven driveway). Of course I replaced the rear axle speed sensor which did not help.
To make the story short, there is a ground connection bar in the battery compartment under the stairs on the passenger side of the coach. It is a little hard to get to and it has four 3/8 holes with ground connections. Three are for the house and engine batteries and one is for what appears to be the ground wires that go to important components like the PCM. I removed ALL the battery cables, lengthened the ground PCM ground wires (which were too short and may have been pulled when the coach flexed) and replaced the ring terminals on the PCM ground wires with soldered (not crimp) terminals.
There is also a separate chassis ground stud near the ground bar with a single ground wire attached.
I sand-blasted the chassis ground connection bar to bare metal (where the 4 grounds attach to the chassis) and the lone ground stud and also sand-blasted the end of each battery cable and the positive stud in the battery compartment where all the positive cables connect. Essentially, I cleaned everything to metal that needs to conduct current to bare metal.
I have only driven the coach twice but there is no stalling and no trouble codes and no pending trouble codes.
The work takes 4 to 6 hours because the ground bar is not easy to get to and all batteries have to be removed. Be sure to make a wiring diagram before you start disconnecting things. And be sure to go to bare metal and tighten everything well. A small sand blaster is really essential because its very hard to get to the ground bar with a file or Dremel tool.
If you are willing to invest 6 hours you should try this before you start replacing expensive components because it costs almost nothing.
