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Jared D
Jared D, ASE Master Mechanic
Category: Transmissions
Satisfied Customers: 1782
Experience:  Shop Supervisor at County Fleet
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08 pontiac soltice 2.4 eng vehicle at ghway speeds when gas

Customer Question

08 pontiac soltice 2.4 eng vehicle at highway speeds when gas pedal is pushed a little bit the vehicle downshifts by it,s self and will not come out of the lower gear until you let up off pedal and coast for a while. saw a glich when grafting the app sensor so replaced the pedal assy customer drove vehicle for 3 days until it happened again on a longer drive .
I did not get it to do it my self but customer did show me a video when it did it.
Submitted: 1 year ago.
Category: Transmissions
Expert:  Jared D replied 1 year ago.

I assume there are no codes right?

Check the transmission fluid level. I know that sounds weird, but If this transmission is even slightly over filled it will do exactly what you are describing and won't set any codes. The trick is to get the transmission to show between 86-122 degrees on the scan tool and then check the fluid level idling in park. If a bunch of fluid pours out of the check plug just let is run out until there is just a little dribble then plug it up. It's a terrible way to check a fluid level, but that's all you can do on this model.

Customer: replied 1 year ago.
you re right with the no codes but the fluid level is right on the money customer wanted fluid change pan was clean ad the problem
was there be fore and after any other sugustion.
Expert:  Jared D replied 1 year ago.

The only other thing I have heard about on this type of car is that it will not up-shift until the pedal is released if the exhaust system is restricted. For some reason the exhaust backpressure prevents the TCM from sending the shift command if there is more than 2 PSI of exhaust backpressure.

The only real way to test it is to remove the catalytic converter and drive drive it without it and try to duplicate the problem. You would have to go through the trouble of mocking up a straight pipe, and you are also going to trigger p0720 codes, but other than replacing the cats outright that's the only way I can think of to test it.

Someone might offer an exhaust pressure testing device that screws in in place of the upstream O2 sensor, but I've never used one.

Expert:  Jared D replied 1 year ago.

I just wanted to check in and see if you needed any additional information on this question? I haven't yet seen a response from you since my last suggestion and was hoping to help in any way I can.

Expert:  Jared D replied 1 year ago.

I hope I have been of some assistance and would really appreciate a positive rating. Please let me know if there is anything I can do to help in the future.

Customer: replied 1 year ago.
The dealer already went that route and replaced the exhaust cats. Still has problem again the transmission sensor and computer comands look to be well with in specifications. trim information right on also.
Expert:  Jared D replied 1 year ago.

Ok. Well I don't think there is much more insight I can offer on this one without being able to check it out in person and see the problem myself.

I hope you get it sorted out!