2016 Infinity QX80 throwing Transmission code P1734

Deere Guy

Newbie
Joined
Mar 12, 2024
Messages
4
Points
1
Make
Infinity
Model
QX80
Year
2016
Miles
92000
Engine
5.6 Liter
Hello All,

New to forum.
I have a 2016 Infinity QX80 with 92000 miles.
Was having a problem with the engine rpm surge / fluctuating and converter chatter.
I changed the transmission fluid with OEM fluid and also added a friction modifier to it.

Went on test drive of about 5 miles and the problems I was having were gone.
No engine RPM surge and no converter chatter.

I took on a longer drive later and at 20 miles it goes into what I would call limp mode.
Wouldn't go over about 40 mph.
Throwing code P1734.

If I take the transmission to manual when it does this, It's in 5th gear and will not go to 6th gear.

Also, If I shut the car off and then drive again all seems fine for approximately 5 miles and then goes into limp mode again.

The problem with the engine RPM surge and the converter chatter are still gone.

Thanks in advance for any advice!

David
 

bp042665

transmission guy
Joined
Nov 26, 2012
Messages
818
Points
28
Location
Iva South Carolina
this code is for a 7th gear ratio code could be a possiable stuck valve or electrical but also a internal leak at a seal. try to drive it in manuel shift mode and only shift to 6th gear and see if it goes into limp mode
 

Deere Guy

Newbie
Joined
Mar 12, 2024
Messages
4
Points
1
Thanks for the reply!

I took it to 6th gear and drove it for about 24 miles tonight and then it went into limp mode.

After it went into limp mode I stopped and turned car off and started back.
I started driving again and went to manual and found out what my RPM was at 60 mph when
shifting into 6th and 7th gear. I did this because it doesn't show the gear it's in when in automatic.
It appears it's shifting into 6th and 7th gear in auto based on my speed and watching the rpm's drop when it shifts.
I drove another 40 miles the second trip and it didn't act up. I'm not saying it's fixed just some info.
There is still nothing that appears to be a problem as to how the car drives or shifts.

So in my original statement I said it wouldn't go into 6th or 7th gear.
I'm certain that was because of the lower speed I was at in limp mode.
Didn't have any trouble shifting in manual to those gears tonight.

Thanks again for your time.

David
 

Mrs.meyer

Newbie
Joined
Apr 7, 2024
Messages
4
Points
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I am having the same issues with my infinity. Have you had any success in figuring out the problem? I am going to have infinity check the TCM box to see if there is a malfunction and then check the solenoids.
 

Deere Guy

Newbie
Joined
Mar 12, 2024
Messages
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Points
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So after my last post it continued to throw the P1734 code and go on to limp mode for another 200 miles or so. I just continued driving it hoping it would clear up since it didn’t start till I changed the fluid. First it got where we could drive longer distances without the issue. Then luckily it just cleared up. It hasn’t caused a problem for approximately 1200 miles.
Wife even took it to beach on a 1000 mile trip with no problems. I wish I could tell you what the problem was but I don’t know.
This car did sit for a week from the time I started the fluid change. It’s typically a daily driver. I wondered if there was a solenoid valve that possibly could have gotten sticky sitting for a week and just time freed it up. Probably not but just a thought. This is my wife’s car and she did say that when it typically threw the code and went into limp mode she was starting to go up a hill or grade.

Good Luck!
Keep us updated on what you find out.
 

bp042665

transmission guy
Joined
Nov 26, 2012
Messages
818
Points
28
Location
Iva South Carolina
most likely you had a valve in the valve body stick you could try a bottle of lube gaurd platium to keep it from sticking again
 

Mrs.meyer

Newbie
Joined
Apr 7, 2024
Messages
4
Points
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Infinity is wanting me to replace my whole transmission and they also stated that I needed new fuel injectors as it was running lean. I have taken it to multiple shops and nobody can guarantee that the problems I am having will be fixed with a new transmission. It’s hard to pay $10,000 when they can’t guarantee it.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,960
Points
63
List your specific problems/symptoms, in your own words, along with any codes set. I suggest you start a new thread, to avoid confusion.

Yeah, $10K is a pretty painful blast of the "parts cannon". Post where you are located, somebody here may be able to recommend an independent shop that is more reasonable.
 
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