99 Durango O/D off light comes and will not go off

The O/D off light will come on the truck comes out of OD and will not go back into overdrive. Turn vehicle off and restart it will act normal. It may be fine for a few days then it does it again. Any ideas
Andy
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Could be a faulty temperature sensor in the transmission. The PCM will lock out OD if it thinks the fluid is too hot. The only way to know for sure is to hook a DRB3 (dealer scan tool) and see what temperature the sensor is reporting. If it's the sensor, replacement is simple enough, but you should make sure that's what's wrong before just replacing it. The PCM may also set an OBD-II code for trans temp., which could be picked up by any generic OBD-II scan tool.
I take it there's no drivability problems with the transmission? No slipping, or anything else that might actually cause the trans fluid to overheat? A non-contact IR thermometer pointed at the transmission pan could verify the fluid temp - if it's under 140F or so, everything's fine.
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The trans works fine and the fluid is not burnt. I have a generic scaner and i will keep it in the car till it happens again. where is the temp sensor thanks andy

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How often has the fluid been changed? How about the filter? OD will come off if the tranny is getting hot.
Andy wrote:

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Part of the governor pressure sensor, in the valve body
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had initiated the no OD mode and it was "stuck" until you discovered that off/on/restart would "reset" it? Have you used the "OD/off/on" switch very often? I am guessing that you very likely seldom if ever use the switch, which leads to my "theory" of the root cause of the problem:
It almost sounds as if the "OD/off/on" mode switch has slightly corroded internal contacts, maybe from lack of, or even no use. I assume when you first noticed the behavior you cycled the OD switch several times convincing yourself that it could not be changed via that approach. The switch cycling may have been juist enough to "clean" the internal mechanical contacts slightly allowing it to regain functionality after you turned it off and restarted it. Then, after no further use the corrosion/dirt would again "contaminate" the contacts after a few days. If my theory is anywhere close to the reality, then the problem shouldn't come back if you make a point to cycle the switch several times each time you operate the vehicle. The cycling would keep the corrosion at bay(at least until you could verify or invalidate my idea) via the friction from the contacts opening and closing on a regular basis. Easy enough to verify or prove the theory wrong.... regards, Joe (were there any unusual OBD-II scan codes logged? Perhaps another thing to check to get more info on the issue, most auto parts store chains will either loan you a scanner, or do it for you at no cost these days...)
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