2005 G35 Auto - codes (P1716, P1815)

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2005 G35 Auto - codes (P1716, P1815)

Postby cfauvel » Fri Jan 10, 2020 8:37 am

ok so in the mornings when cold (florida cold, so we're are talking at worst 50 degrees), the trans shifts REAL hard going up and down(throws the codes), until it warms up, then it behaves.

so P1716 is the turbine revolution sensor, which is the first sensor (closest to front of car) on the tcm (Transmission Control Module - on the valve body itself)...not replaceable by itself. Don't know what the second sensor is called that is right next to it(again on the tcm)

Someone I spoke with who sells remanufactured valve bodies says the sensors need to protrude through the tcm's plastic housing the thickness of two nickels. If it is 1mm short of that the sensor might not read the speed and throw the code.

P1815 is the manual switch circuit...now when you use your shift lever and push it to the right to go into Manual Mode that depresses a micro switch and tells the tcm that you are in manual mode, when you push up on the lever it momentarily presses another micro switch and tells the tcm to up shift, and when pulling back on the lever there is yet a third micro switch to tell the tcm to downshift.

My problem is I don't know if P1815 is referring to the shift lever's switches or the switches inside the tcm. I suspect it is inside the tcm

I have a nice scanner that reads live data from various systems, and under the transmission system I can read live data from the micro switches and see that the micro switches does indeed tell the tcm that the switch is on or off .

My gut is NOW telling me that when the TCM can't properly read the Turbine revolution Sensor's speed, it puts the transmission in Limp Mode (or similar) and prevents Manual mode (when the transmission acts up the display on the dash stays as D even if I try to go to manual) and throws P1815 too.

has anyone drop the valve body, taken off the TCM and inspect the two sensors to see if the amount they protrude can be adjusted?

Two places I found that remanufactures valve bodies are
https://streetsmarttransmission.com/rem ... alve-body/ - and will cost $740 (in Tampa, Florida)
www.softelectronic.com (out of Bulgaria of all places) and will cost $400...I don't think I'll go that route
(the valve bodies need to be flashed properly for your specific vehicle so be careful with that....both companies will do that)

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Re: 2005 G35 Auto - codes (P1716, P1815)

Postby audtatious » Wed Feb 05, 2020 3:56 pm


Don't know if you have looked through the FSM for this but it's linked above. This could be anything from faulty switches and components to bad electrical connections. Unfortunately I don't work on transmissions and can't help too much. Based on what you are seeing it seems to not be the micro switches but I would check proper continuity anyhow.

Good luck, hope you figure it out.

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Re: 2005 G35 Auto - codes (P1716, P1815)

Postby cfauvel » Thu Feb 06, 2020 7:05 am

Thanks for the reply , yep read the sections over and over again.

I've come to the conclusion that the TCM is putting the transmission into a mode that Manual Shifting is disabled when it throws the 1716. So concur that the microswitches in the shifter is NOT the problem.

So here is our new SOP (standard of operation).
We warm up the car to operating temp for about 5-7 minutes, before we attempt to drive it. AND surprisingly that DOES IT!!

Using my new scanner and reading live data of the engine rpm compared to input shaft rpm....I can see that ONCE warmed the RPM are close to being even, which is what the FSM says it should be....when cold the numbers are WAY off and when the CEL will come on and shifting acting poorly.

SOOOOOOO at this point I believe it IS an electrical connection on the TCM that makes a proper connection once the fluid is warm.

Just haven't dropped the valve body yet to inspect the TCM....and not sure I would find something either....

It is a messy job...but a couple of hrs to drop could lead me to finding the bad connection....but it could also NOT.....I am 99.99% a NEW-to-me remanufactured valve body would resolve everything...

I'll keep this thread updated.

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