Question about 2009 Hyundai Sonata

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My 2009 Sonata cruise control causes the transmission to shift down on every minor grade. Causes me very poor fuel mileage and has to shorten transmission life. Shifts 1 or more times in most every mile.I read on a forum that you can lock the shifter into overdrive which does help but then the torque converter shifts in and out of lock-up all the time. I don't know if this hurts the torque converter but it still lowers fuel mileage. No help from Hyundai, they say this is normal on 2009 and newer models and there will be no repair. In my 62 years I have never owned or driven a car that does this includeing other Hyundais.

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I have a 2009 hyundai sonata v6 should I have the auto transmission flushed. I have been told I would have problems after?

Transmission services are part of routine maintenence. Flushing the system on a high mileage vehicle where the fluid has been neglected can cause issues as it stirs up and removes deposits of varnish and worn band/clutch debris through out the system. Most vehicles are usually drain and fill. Others are pan removal with filter and fluid change. Not many companies still do "flushes" but will recommend one of the above services be performed during routine maintenence

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P0826 Nissan - Rogue 2009

P0826 Nissan - Manual Mode Switch Circuit
Possible causes: - Faulty Manual mode select switch (Built into control device, shifter)
- Faulty Manual mode position select switch (Built into control device, shifter)
- Faulty Control Device (Shifter)
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- Control Device circuit poor electrical connection

When is the code detected? When an impossible pattern of switch signals is detected, a malfunction is detected.

Possible symptoms: - Engine Light ON (or Service Engine Soon Warning Light)

P0826 Nissan Description: Manual mode switch is installed in shift control device. The manual mode switch sends shift up and shift down switch signals to Transmission Control Module (TCM) with Control Area Network (CAN) communication.

TCM sends the switch signals to combination meter via CAN communication line. Then manual mode switch position is indicated on the shift position indicator.

P0826 Nissan Manual Mode Switch Circuit

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1 Answer

05 sentra 1.8 L transmission speed sensor and vehicle speed sensors have both been continue to come up and vehicle randomly miss shifts then cruise is inop. Also shifts back and forth...

after having replace sensors with new items ( not 2nd hand units ) and the codes reappear then the problem was not fixed by the sensor replacement. IN the list of possible causes for the codes ,the TCM will be a prominent failure point and the wiring and connects are next. Down the list will be mechanical failure and this need to be checked out by a pressure test being done on the transmission, adjustments to the band and clutch packs. Check all wire connections for clean pins and tight connections . The cruise controls requires a constant circuit for it to work so that any failure of a circuit indicates the need for the driver to resume control of the vehicle ( braking-)

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Possible causes of this code are: - Low transmission fluid level
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Read more:

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1 Answer

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These are a few questions I need to know to try to isolate the problem, but to put you in a ballpark of possible causes, causes could be (but not limited to):
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a faulty map sensor
a faulty egr valve
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low transmission fluid level
partially or blocked transmission fluid filter
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I don't know from where you bought the car but do you feel certain that typical causes such as fouled plugs or clogged air filters are not at fault?
Most dealers, even the shlocks don't normally skimp on the simple stuff but who knows about a private source?
That does seem low, especially the city numbers. I don't think Hyundai is any leader in gas mileage but they are better than what you are getting.  

Dec 24, 2008 | 2006 Hyundai Sonata

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