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Discussion Starter #1
2016 Limited LT. ENgine light came on this evening. I used my cheapo scan tool a couple different times and it can't seem to make up its mind. ONe time it threw P700 and P711, the second time it threw just P700, and then after running another errand, it went to just P711.
Checked Google and all I can find is these are generic codes for Trans control system and trans temperature sensor circuit range/performance.

The drivetrain is still under warranty for a few more years and I will be calling the nearest dealer first thing tomorrow. Curious if anyone has seen this and can give me a heads up on what to expect?
 

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I have seen it. Not very common issue and is for transmission temp sensor performance. The transmission temperature sensor is an integral part of the TEHCM assembly, aka TCM and electric valve body assembly, and will more than likely will need replacement. It's a 4+ hour job so bring a good long book if you decide to wait at the dealer to have it fixed.

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Discussion Starter #3
Thanks, that sounds reasonably likely. It must be rare, because my search on the forum for these turned up nothing. And this encyclopedic knowledge in this forum is massive.
 

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P0700 simply means the TCM has requested the MIL lit because of a transmission malfunction.

P0711 Is a performance code that indicates the TTS (transmission temperature sensor) is not changing value in a predetermined amount of time.

I would make sure the wiring and connectors are not at fault before digging into the transmission. Make sure your battery and the grounds to the engine are in good nick too.

For those that have a 2011 or earlier... The TTS is mounted below the valve body in the 4T65E. You have to drop the LH end of the engine/transmission cradle and pull the LH half shaft to pull the side cover so you can access the valve body. If you're digging into it that far I'd replace both shift solenoids along with the TCC and Pressure Control solenoids in the valve body.

The 2012-2016 6T7x valve body isn't serviceable without pulling the transmission.
 

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My reader showed it as P700. Maybe it was made in China and they leave off the extra zero to save on production costs.
Probably due to how the software is written. I'd bet it's set up to only display the first non-0 character - ie, it's not set up to display leading 0's. So when it sees 0700 come across the CAN bus, it gets displayed on the screen as 700.

Chances are the software writers for the reader aren't car guys and know just the bare minimum to implement this type of application.

Doug

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P0700 simply means the TCM has requested the MIL lit because of a transmission malfunction.

P0711 Is a performance code that indicates the TTS (transmission temperature sensor) is not changing value in a predetermined amount of time.

I would make sure the wiring and connectors are not at fault before digging into the transmission. Make sure your battery and the grounds to the engine are in good nick too.

For those that have a 2011 or earlier... The TTS is mounted below the valve body in the 4T65E. You have to drop the LH end of the engine/transmission cradle and pull the LH half shaft to pull the side cover so you can access the valve body. If you're digging into it that far I'd replace both shift solenoids along with the TCC and Pressure Control solenoids in the valve body.

The 2012-2016 6T7x valve body isn't serviceable without pulling the transmission.
The valve body on the 6t75e transmissions are serviceable without pulling the trans, I've never had to remove a transmission to service either the mechanical nor electrical valve body.
There is no wiring to check in the 6t75 transmissions for the trans temp sensor since all the wiring is integrated inside the TCM and electronic valve body, way different than the older 4t65e transmissions witch had an internal wiring harness that could be tested from outside the transmission since the TCM was located outside the trans.
The only test you can do on these 6 speed transmissions is use a scan tool that can display transmission live data and monitor the transmission temp sensor and the temp should steadily increase to normal operating temperature then stabilize, also check after the trans fully warms up the transmission fluid temp and TCM temperature should be within 20 deg C (36 deg F). If not, you need a new TCM and electronic valve body assembly.

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You may be able to monkey with the valve body and TCM with the transmission installed but it ain't gonna be fun.
IIRC... There's not a lot of room between the valve body cover and the front body crossmember under the radiator.
I suppose you could pull the radiator for a bit more room but it looked like it'd be darn tight on the last 6 speed Impala I looked at.
 

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Discussion Starter #10
Update:
I think I mentioned the engine light turned off on its own after a day. So when I called the Chevy dealer, they said there was no point bringing the car in since the engine light was back off. They said something to the effect that they can't diagnose anything unless the malfunction code is actively happening when they run the diagnosis. They said just knowing a P0700 code doesn't narrow down the problem down much.
About two weeks later and the engine light has come on and turned off within a day yet again. Once again, the stored code showing on my scan tool is P0700.
So are the Chevy mechanics incompetent, lazy, avoiding covering the certified warranty; or can they really only diagnose something if the error is happening constantly such that the engine light stays on all the time? Do I really need to wait for the TCM (or what ever the problem is) to fail so completely that they can diagnose it? Depending on what the problem is, couldn't this cause extra damage to the drive train while I wait?
 

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^+1. Those seem to be pretty generic codes. P0700= trans. control system malfunction. P0711= trans. fluid temp. (TFT) sensor circuit range/performance.
 

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As Sheila says. P0700 is a very generic code that literally means the TCM has requested that the ECM light the money lamp.
P0711 is a little less generic but it needs to be diagnosed with the problem present.
Intermittents are very frustrating for mechanics and customers. If the fault is not manifesting when you're troubleshooting you're stumbling around in the dark.
Intermittents that only show up occasionally generally turn out to be electrical issues. Your garden variety dealership isn't likely to have a good electronics tech on staff. Automotive electronic troubleshooting is a pretty specialized trade amongst automobile and truck mechanics and it isn't in the flat rate books so you can pay dearly for it if you can find a real expert. If you have the ability and the tools I'd run some tests with a scope and a meter. You might luck out and discover some odd behavior that's present all the time but doesn't quite make the TCM angry. You might also discover it's not presenting the issue at all when you look at it.
 

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This might sound trite and over-used but I'd clean up the main ground stacks on the transmission, body, and engine. Corroded grounds can cause all kinds of odd behavior. It might not fix a darn thing but it's worth a shot.:)
 

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Discussion Starter #14
Thanks everyone. Nice to hear my local dealer isn't completely incompetent, well, at least based on this issue. I will google/youtube some examples on how to for basic electrical tests and for cleaning ground stacks. May as well rule out a few of the simplest possibilities. After that, I am not really interested in pouring a bucket of money into chasing down a problem that may end up being nothing or may be something covered by the certified warranty. Guess I will just keep an eye on the problem and track the issue to see if any trends show up that might point to what the issue is.
 
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