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Mazda 626 Overdrive keeps shutting off

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New User

Sep 25, 2017, 4:21 PM

Post #1 of 5 (783 views)
Mazda 626 Overdrive keeps shutting off Sign In

My car is a 2000 Mazda 626 2.0L automatic with 137,000. I believe that this car sat for a while before I bought it. There was dry rot all over it when I bought it. From the tires, to the axle boots.

The overdrive keeps turning on and off randomly. The switch on the shift lever rarely has any effect on turning the OD on or off, but it does every once in a while. The OD off light never flashes (which I believe indicates high temperatures), it just comes on, and you can feel the transmission change to a lower gear, or the car just does not go into high gear at higher speeds.
Two years ago when I bought it, I had the transmission rebuilt. The shop knew that this model of transmission was a common problem on this car, and installed heavier parts. On a mazda626 forum, I read that the neutral safety switch can cause this problem, so I replaced that. The problem still exists. I have deducted that the transmission itself is probably not the problem but it must be some type of sensor, or electrical. But nowhere I look can I find a solution to the symptoms. Some have said it could be low fluid, but not here, and there is not a transmission fluid leak. Some said high temps, but the OD off light is supposed to flash when that happens, and the fluid does not smell burnt.
If a pattern exists, I cannot figure one out. The OD off light is what I refer to here. When I start the car, rarely does it start with the OD off light on. But it can come on nearly right away, or it may drive a few miles before coming on. And you can feel when it comes on, as the car down shifts. Most of the time it does come on while the car is stopped and running though, or at low speeds below 40 MPH. Never above 40 mph. Once the light comes on, it does not shut off. If I shut off and restart the car, usually that seems to reset it for a while. Once in a while I can drive the car more than 10 miles without the OD light coming on.

(This post was edited by Novicemech on Sep 25, 2017, 4:24 PM)

Ultimate Carjunky / Moderator
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Sep 26, 2017, 7:10 AM

Post #2 of 5 (754 views)
Re: Mazda 626 Overdrive keeps shutting off Sign In

Someone needs to connect a high end scan tool up and monitor the OD switch status and the TCC solenoid command when the problem is occurring. With that information you can get direction on where to look for the issue. It is either going to be an input issue or and output issue and the only way to know is to monitor transmission data stream information or connect up meters or scopes to those circuits involved with TCC apply to see what is actually going on.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Sep 26, 2017, 7:54 AM

Post #3 of 5 (747 views)
Re: Mazda 626 Overdrive keeps shutting off Sign In

You for sure need this scanned for codes, on this transmission, the A solenoid which is internally grounded goes bad, when this happens it knocks it out of 4th gear, you may have a P0750 code stored. Gary

New User

Sep 26, 2017, 9:45 AM

Post #4 of 5 (739 views)
Re: Mazda 626 Overdrive keeps shutting off Sign In

Thanks, good info. I'll take it in to have them hook it up. I was hoping it would be a quick fix. I'll let you know what they find.


Sep 26, 2017, 12:21 PM

Post #5 of 5 (726 views)
Re: Mazda 626 Overdrive keeps shutting off Sign In

ok, let me know what they find. Gary

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