Reading GM/Delco's Mode 6 for P0711

[dwchapmanjr]

I got the dreaded P0700 & P0711 on Monday on a 2015 GMC Yukon Denali.  Cleared the code and it came back.  MIL hasn't iluminated yet so I'm waiting on another drive cycle before I schedule an appointment with the dealer.

In the meantime I wanted to understand the conditions of P0711.  GM has a great PDF but I can't quite understand it.

 

https://gsi.ext.gm.com/gmspo/mode6/pdf/2015/15OBDG08A Transmission Diagnostics.pdf

 

I don't quite understand how to apply the table to the conditions.

 

Further to add confusion, my scan tool is reading -40F for TFT although in tow mode my transmission temp reading hovers between 125 and 150.  I did watch it once and see it dip to 100 flat from 125-150 for a brief moment so I imagine its just a flaky sensor but I'm more curious about what triggers this based on those conditions.

Edited September 23, 2020 by dwchapmanjr
spelling

[Jsdirt]

A -40° reading on the scan tool is a dead ringer for an open circuit ( if I don't have that backwards ... ). Bad sensor, open in the wiring, or poor pin fitment / bad connection in the connector.

[dwchapmanjr]

I am sure the sensor is flaking but my my only hesitation on the open is maybe my scan tool is trying to read a wrong value because the dash is getting a value from something. Other people that have had the fluid sensor go out say the dash acts up or stays at 100.

 

More just curious to understand the conditions from the tables.  Any ideas on how to apply the 2d table to the conditions?

[Jsdirt]

It's all greek to me. Disconnect the sensor and look at what the scan tool is reading. Then, connect a INCANDESCENT (NOT LED) test light across the pins, shorting them together though the light. If the scan tool now reads some elevated temp in the upper 2- 300° range, then the wiring and the gauge is good. Just be aware this still doesn't rule out a loose pin fitment issue in the connector, or corrosion there. If the pins feel like they're gripping tight, and you're sure you have a good connection, replace the sensor.

[dwchapmanjr]

Interesting way to test. I will leave it to the dealer as I have a GM Protection Plan and hoping this is covered. Upvoted your answer, thanks for the info. If anyone else knows how to read that chart though I'm still interested in learning that. 

[Jsdirt]

Thanks, David. Yeah, hopefully you're still covered.

[dwchapmanjr]

For what its worth, my Foxwell NT510 Elite did seem to be reading a wrong value.  They sent me an updated fix and I see temps now so I'll graph it.

[dwchapmanjr]

I did find this on an unrelated but GM vehicle but I don't understand the terminology.

What is the TCM substrate temp and what is the power up temp?  Are there other temp sensors on the transmission?

Quote

• TCM detects a 36-90F or greater difference between the transmission fluid temp and the TCM substrate temp which depends on the average of the trans fluid temp, TCM substrate temp and TCM power up temp.
• TCM detects a 36-90F or greater difference between the trans fluid temp and the TCM power up temp, which depends on the average of the trans fluid temp, TCM substrate temp and TCM power up temp.
• Above conditions have been met for 5 min within a 6 min period.

 

[Doug_Scott]

Did you see this already..  https://www.dtcdecode.com/GMC/P0711

 

Also found a line in your original pdf link that says "TCM internal temperature (substrate)"  To me that means in their minds, substrate is internal temperature. 

 

Don't know why they would toss a different word there when they already had a nice descriptive phrase that was easy to understand.  I could understand it if this document was hand written, having to manually write out TCM internal temperature many times would make it worthwhile using a shorter word.  But this is a pdf file.  Just put the repetitive long phrases that are commonly used into a paste buffer, and use the couple of key strokes to paste the phrase in.  Substrate is not even close to being useful in describing anything to do with transmission temperatures.   

[dwchapmanjr]

3 minutes ago, Doug_Scott said:

Did you see this already..  https://www.dtcdecode.com/GMC/P0711

No, that's exactly what I'm looking for!  Human readable terms for the condition.

4 minutes ago, Doug_Scott said:

Also found a line in your original pdf link that says "TCM internal temperature (substrate)"  To me that means in their minds, substrate is internal temperature. 

Interesting, so that would imply there is a temp sensor somewhere other than the fluid?

 

I ended up finding a freeze frame on the code which was helpful and showed a TFT temp of around 48F which likely meets condition 3 as I imagine it dipped while driving.

 

Quote

• Condition 3
• The TFT changes 20°C (36°F) or greater in consecutive readings 14 times in 7 seconds.

In any case, thanks for sharing the DTCDECODE, I don't know why I couldn't find that before.  I still don't understand the charge of the "axis and curve" tables but now I don't have to.

[Doug_Scott]

3 hours ago, dwchapmanjr said:

No, that's exactly what I'm looking for!  Human readable terms for the condition.

Interesting, so that would imply there is a temp sensor somewhere other than the fluid?

 

I ended up finding a freeze frame on the code which was helpful and showed a TFT temp of around 48F which likely meets condition 3 as I imagine it dipped while driving.

 

In any case, thanks for sharing the DTCDECODE, I don't know why I couldn't find that before.  I still don't understand the charge of the "axis and curve" tables but now I don't have to.

I found it by clicking a link inside a link.  I wonder if they are actually talking about the fluid when they say "substrate".  It is still a completely incorrect use of the word, after all, fluid has less letters, with ATF having only the 3 letters.  The dip in temperature that is instantaneous (for ex. 102°F change to 48°F in one step) would indicate a connection issue.  The connection issue could be in the connector at the temp sensor, or one of the connections back in the harness.  I would expect to see corrosion in that connection if it is loose.  You could get the transmission hot, then put the front end of the truck on stands, and take your scan tool under the truck with you or have someone watch the temp its displaying while you go under the truck and jiggle the wire at its connection points looking for a temp change of more than a degree at a time.  No idea how much a sensor is, but, if it is one of those $10 ones, just change it.  Time it takes to check it is longer than $10 worth of time.  Check connections first though.

 

Back when I became a mechanic you had to be 18, and have at least a grade 10 education.  We have had licensed mechanics at least since the end of WW2 in Ontario Canada.  Growing up it was common to hear parents say that if little Jimmy doesn't smarten up he will end up being a mechanic, plumber or tv repairman.  Now you have to have some 2 year college course in order to technically get a license.  And even after making the education change, no mechanic would ever use GMs definition of substrate.  My first guess was the stuff you put under paving stones in your driveway.  Then again, I only left high school with my grade 10.  Having fun was much entertaining than school.  Besides, I wanted to be a mechanic.

[dwchapmanjr]

2 minutes ago, Doug_Scott said:

The dip in temperature that is instantaneous (for ex. 102°F change to 48°F in one step) would indicate a connection issue.

Would not surprise me.  This is on an 8L90 which is known for its temp sensor issues.  Its part of the wiring harness in the transmission pan.  If I have the single piece harness the valve body has to get removed too but I think its a two piece.  A bit more than I want to get involved with since I have a GM Protection plan.  I can do some basic mechanical stuff but want to waive voiding the warranty and generally not comfortable dropping the pan on a transmission.  But I can plug in a scan tool and read codes and freeze frames like nobody's business!

Freeze frame on it has shown a failure 3 out of 11 times, 7 passes and one canceled test.  The thermostat isn't opening so the issue may be that the sensor is not very accurate at the lower temps or it could be starting to flake out.  When its a cold start in the morning, the fluid sensor does read within 10F of ambient temp and close to coolant temp.

 

I took a few years of advanced chemistry in higshcool and college and I don't ever recall using the term substrate.

[dwchapmanjr]

For what its worth, even-though its tangent to the topic.  I brought it in and they caught the temp reading -48F.  Replaced harness because they detected high resistance and temp hung around 175.

[Jsdirt]

"Substrate" in the automotive world is a strange term. It's stuff like this that makes me firmly believe that automakers are actively attempting (and succeeding) in sabotaging DIY repair attempts with confusing terminology, and illogical part design, location, and assembly. I sure wish I stockpiled vehicles from the 30's to 1972, when I was younger ...

 

Not surprised with the harness - always either a bad sensor, or bad connection. Bad connections & broken wires account for a large percentage of failures up here. They've even managed to cheap out on wiring by using tiny wire gauges, and substandard copper.

[dwchapmanjr]

3 minutes ago, Jsdirt said:

"Substrate" in the automotive world is a strange term. It's stuff like this that makes me firmly believe that automakers are actively attempting (and succeeding) in sabotaging DIY repair attempts with confusing terminology, and illogical part design, location, and assembly. I sure wish I stockpiled vehicles from the 30's to 1972, when I was younger ...

 

Not surprised with the harness - always either a bad sensor, or bad connection. Bad connections & broken wires account for a large percentage of failures up here. They've even managed to cheap out on wiring by using tiny wire gauges, and substandard copper.

To me, I am amazed that electronics and wiring can be submerged in transmission fluid and work properly.  I realize this is common place but still amazed me the first time I saw it.