Stuck in high gear after period of time at highway speed?

2009 MERCEDES BENZ E320
150,000 MILES • 3.0L • 6 CYL • 2WD • AUTOMATIC
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RYAN.TIM.J
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Hi, E320 3.0 V6 Diesel. Drives great around town. When on highway, gets stuck in overdrive, will not downshift when you step on gas to accelerate. Have to downshift manually. Getting off highway, seems to be stuck in higher gear than it should be. Goes back to normal after turning car off but goes back to stuck condition when going highway speed again.

Check engine light was on, but no engine codes when reader connected. I "erased codes" and the light went out.

Could this be a sensor on the engine? Like a throttle position? Or is it in the transmission?

Any guidance is greatly appreciated.

Thanks,
Tim
Jul 4, 2023 at 4:44 PM
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STRAILER
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This can be a problem with the adaptive learning program, to restart this process, please check out this video:

https://youtu.be/BQkj3UK37u8

If this doesn't work the turbine shaft sensor could need replacement. Also, we should check the transmission fluid level and condition, this guide may help as well. Please check the images below for instructions on your car.

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

For transmission 722.55 in model 164.195 (ML 450 hybrid)

Type .................... DEXRON VI

If the fluid is burnt, I would check the fluid and filter. Here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car:

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Check out the images (below). Please let us know what happens.

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Jul 5, 2023 at 12:42 PM
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RYAN.TIM.J
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Thanks Ken,

There were two pictures attached to the reply, looked inadvertent. The first two are for Lincoln A/C compressor, were there two others intended?

I have been changing A/T fluid every 40k miles, so I hope it is not the fluid, if burnt, would be an indicator of something bad.

That speed sensor is on the bottom accessible with the pan off, picture is upside down? Or is that picture identifying it right side up, have to dig through several layers to get to it?

I right side up, I have no experience rummaging though transmissions, might leave this to a shop.

Thanks again, this website is always so helpful.
Jul 5, 2023 at 5:31 PM
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STRAILER
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No problem, please let us know how it goes.
Jul 6, 2023 at 10:06 AM
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RYAN.TIM.J
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Does anyone know where the boost pressure sensor is on this model? For the v-6 turbo diesel?
Aug 21, 2023 at 1:39 PM
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STRAILER
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Sorry, we only handle one problem per thread, please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
Aug 22, 2023 at 10:35 AM