Odd transmission (seemingly) issue

[ZiggyStardog]

My 2008 Versa S Hatchback with non-CVT automatic transmission has been acting up since the battery went dead.

Had the battery replaced, and everything was fine until a few days afterwards someone mentioned that the brake lights weren't working.

Replaced the bulbs (per instructions in this forum), and still NG-- so I replaced the switch for the brake pedal, and the brake lights worked.

The next day, went for a longer trip and then the engine and/or transmission apparently went into a limp or failsafe mode with no check engine light. Car sat for a while, and drove about 15-20 miles at highway speeds no problem. Day after that drove fine for a couple 4 or 5 mile trips, and then went into failsafe/limp mode again.

While in this mode car drives increasingly more slowly, until it won't do much more than 20-25 MPH. Contrary to what I've heard about failsafe mode, it will use 1st and 2nd gears as well as third depending on how fast it allows you to go. Stop engine, and let sit for a while, and it will behave normally for about 4-5 miles and it starts up again. AT fluid levels seem okay, fluid could use changing but haven't done that yet.

Tried to read engine codes both the manual methods and a code reader to no success. Check engine light doesn't come on. Tried manual reset of ECU, no difference. Found procedure to read TCM "codes" and get P0720 which is supposed to be a "AT revolution sensor" but the manual says something about if you are in failsafe mode, you'll always first get this code and more beyond that or some-such.

While in this mode, transmission seems to "drag" as if you have more engine braking than usual. Engine also appear to hesitate or knock or something like that, but it's hard to tell. Also requires you to press the accelerator to move forward whether in reverse or neutral, doesn't "creep". Yet, start it from a cold start and everything behaves normally for about 5-6 miles or so.

I never went of automatics much... too complicated, and too much to go wrong. But I don't drive this one much. I'd like to have a clue as to what's going on before I take it in.

Anyone have any ideas? Is this truly failsafe mode, or is this something else? Thanks.

[Athikerguy4life]

Take it to the dealership. Unless you're over 50,000 the transmission is still under warranty so they should be able to take care of it for you.

[ZiggyStardog]

Just over 80,000, so no warranty possibilities here. They did cover a bad fuel pump just before it expired, though.

It will probably end up at the dealer anyway, but I didn't need it right away so I thought I ask if anyone had any ideas what this might be, before I take it in.

[Francesco]

Any chance the new brake switch is misadjusted and causing control problems for the transmission?

Frank 2009 Versa S sedan MT-6 with 24000 mi

[ZiggyStardog]

Didn't think so. Replacing was a twist/snap-in, so no adjusting was involved. I suppose I could put in the old one back in and try that minus the brake light function, and see if things change at all.

[Francesco]

Didn't think so. Replacing was a twist/snap-in, so no adjusting was involved. I suppose I could put in the old one back in and try that minus the brake light function, and see if things change at all.

I know that the CVT transmission gets signals from the brake pedal, however, I do not know if 4 speed auto does. Good luck in solving the problem.

Frank 2009 Versa S sedan MT-6 with 24000 mi

[ZiggyStardog]

I think it may only apply to the interlock where you are required to apply the brakes to shift out of park. I have a copy of the wiring diagram, so I'll try to trace this down.