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I had my 2015 infiniti Q50 Engine error code P0720 show up after which I replaced it with speed sensor part # 31935-1XJ0D but the same Engine error code persisted and the transmission jerks and shudders and behaves erratic just like before. Please advise on how to resolve solve this transmission error as I'm confused by the advises given by various mechanics like
1. Replace the entire gearbox
2. It's a Valve body valvetronic issue and to replace it with a new modified TCM valvetronic part # 31705-x985b

PLEASE ADVISE, I'm loosing sleep over this transmission issue as it concerns the safety of my family and those who drive along with me. Many thanks.
 

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How does the harness look? Did you clean it up while replacing the sensor? The next step would be to check the continuity of the harness wires.
 

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Infiniti Q50 '17 Redsport, Dynamic Sunstone. Trunk Strong Arm struts. Red
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Jerky shifting transmission problems solving 101 is to disconnect the battery for a couple hours or overnight. But I'm going to guess this was done during component replacement?
 

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I had my 2015 infiniti Q50 Engine error code P0720 show up after which I replaced it with speed sensor part # 31935-1XJ0D but the same Engine error code persisted and the transmission jerks and shudders and behaves erratic just like before. Please advise on how to resolve solve this transmission error as I'm confused by the advises given by various mechanics like
1. Replace the entire gearbox
2. It's a Valve body valvetronic issue and to replace it with a new modified TCM valvetronic part # 31705-x985b

PLEASE ADVISE, I'm loosing sleep over this transmission issue as it concerns the safety of my family and those who drive along with me. Many thanks.
I have 2015 hybrid and I got the same code plus others codes with it, the dealer told me to replace the entire gearbox.
However, I fixed it by replacing the valve body only with a used one in a small local garage. But you need to reprogram the TCM.
 

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I had my 2015 infiniti Q50 Engine error code P0720 show up after which I replaced it with speed sensor part # 31935-1XJ0D but the same Engine error code persisted and the transmission jerks and shudders and behaves erratic just like before. Please advise on how to resolve solve this transmission error as I'm confused by the advises given by various mechanics like
1. Replace the entire gearbox
2. It's a Valve body valvetronic issue and to replace it with a new modified TCM valvetronic part # 31705-x985b

PLEASE ADVISE, I'm loosing sleep over this transmission issue as it concerns the safety of my family and those who drive along with me. Many thanks.
I'd take it to a dedicated transmission shop to get looked at, the P0720 indicated the output speed sensor is having an issue. If I recall its part of the Valvebody
and Infiniti considered it an (Unserviceable part).

You should be able to find a replacement Valvebody from Ebay or another site for pretty cheap Nissan used that 7-speed
in everything for the better part of a decade.

A DIY thread for this particular problem can be found below if your looking for more info.
2014-16 Q50 3.7 Valve Body Replacement / P0720 Code

2014/5 Q50s with the 3.7s have tons of problems with the valve body crapping out. It wouldn't be out of line of that's what's wrong.
I'd say the valve body is more of an issue with the 3.5L Hybrid Q50 and wasn't super common with the 3.7L.
but it did end up getting a TSB so it could be more wide-spread then what I've observed over the years on the forums.
 
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