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I have a 1999 Dodge Dakota. It is a V6, 3.9 Liter, auto transmission. I have a weird problem that no one has been able to answer for me.

HOW I CAME TO REALIZE THE PROBLEM:

One day I was driving home and had to stop at a stop light. The light turned green and I took off. For some reason it would not shift out of 1st gear at all. So, I was stuck driving at 3000 RPMs and 25ish MPH. I drove to a bank and parked it. The next day I went to get it. I was just going to drive it home and figure out what was wrong with it later. It was still acting the way it did the night before, not shifting. I noticed I didn't have enough gas to get home to I stopped at the gas station and filled it up. When I pulled out of the gas station it started shifting normally again.

So, I have had this happen to me a few times now. It is always when I am really low on gas. Once I fill it up with gas the problem goes away. It usually occurs around an 1/8 of a tank. Why is this happening? How does the level of gas in the tank have anything to do with it shifting?

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  • How low is this? I have seen auto manufacturers wire up some odd stuff in the electronics to ensure the owner's do something, but this is certainly odd - like an unknown bug!
    – jp2code
    Oct 13, 2012 at 1:36
  • You think this was intentional from the manufacturer? I have never heard of anyone else having this problem.
    – Linger
    Oct 14, 2012 at 2:02
  • I doubt it. But, I spend a lot of time on the Nissan Hardbody forum, and Nissan has coded in some strange behaviors whenever it gets bad readings from sensors. It could be that you have water in the bottom of the tank.
    – jp2code
    Oct 14, 2012 at 15:57
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    limiting the rev range and gears is a fairly common "limp-home" mode in many modern case. As Jp2code suggests, it is probably pickingup some sort of error from one of the sensors somewhere.
    – Nick C ♦
    Oct 15, 2012 at 13:08
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    Limiting the user to one gear when it is critical they efficiently reach a gas station seems like a liability...
    – Eric Fossum
    Nov 5, 2012 at 4:19

3 Answers 3

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This sounds like it could possibly be an Evaporative Emissions problem involving your fuel tank. The engineering side of fuel systems refer to the amount of air in a fuel tank as "Head Pressure". Since fluids are almost impossible to compress, as you gain more air (and use fuel) in the tank it's contents are more easily compressed. The vehicle's computer can see the fuel pressure or EVAP solenoids to see if they are falling within specification. Many times when you have a condition where the tank is empty and problems begin, it is due to either a EVAP problem or vacuum related issue. If you keep your tank filled up, you can actually run the engine on a faulty fuel pump for quite some time. The "Head Pressure" of the tank combined with the gasoline's weight will actually assist the pump in pushing it up to your fuel rail when its full. THAT being said, you could additionally have a faulty fuel delivery system and your ECU could be shoving it into limp mode to avoid damage to transmission or engine. Once you fill your tank back up you're essentially making the ECU think the problem is fixed. If it is a vacuum driven transmission, an EVAP leak or vacuum leak from the tank could also cause this.

One other possibility is foreign deposit in the fuel tank. This can temporarily or permanently clog your fuel pump. Once the fluid reaches a low part of the tank, it can cause a concentration of sediment to pool around where the fuel gets pulled into the pump. You would need to do a full diagnostic analysis of the system to ensure it's one of the above problems.

Lets not forget that Chrysler's computer systems aren't the best to begin with lol.

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  • It is a Dodge, not a Chrysler.
    – Linger
    Nov 20, 2015 at 15:51
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    Chrysler Motor Company owns dodge. They purchased it back in 1928 when the brothers that owned the company died. Fiat now owns Chrysler and Fiat owns Alfa Romeo, Chrysler, Dodge, Ferrari, Jeep, Lancia, Maserati, Ram and SRT. Chrysler owned Dodge and Jeep far before Fiat bought Chrysler.
    – cloudnyn3
    Nov 21, 2015 at 0:11
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Maybe when the tank is low you are effecting the vacuum on the engine. Many cars rely on the vacuum to tell the transmission when to shift.

Anyone have thoughts on this idea?

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I have this same problem on a 1999 Dodge Ram 4x4. Didn't start doing it Until it had 50,000 miles on it.

The 1999 has only one oxygen censor and throttle body. That said, itss not not a vary smart electronic system so I wouldn't think the system has a limp mode.

I also remember years ago that a deep snow broke a plastic vacuum line under the trany that causes the 4 wheel drive too stop working. I spliced a piece of rubber vacuum hose on the line to fix it.

I don't recall if the low fuel and shift problem started at this time.

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