6l80 stuck in 1st and dash cluster glitching out

[07blackeddenali]

So I have a ‘07 Yukon Denali 6.2/6l80/awd with approximately 187k and I’ve recently developed an issue that’s a weird one. Couple weeks ago on my way to work the transmission defaulted to 1st gear (only 2.5 miles from my work), let it sit all day and on my way home it was doing the same thing but this time the dash cluster started glitching out going from my speed to 0 and back up again, all my other gauges would stop working also then work and constantly doing this for my drive home. Let it sit over the weekend and has not skipped a beat for the past 1.5/2 weeks I’ve driven it until today where I went to unlock it when I was at the store (drove fine to the gas station then to the store) then all of a sudden as soon as I went to start it the yukon wouldn’t start, cycled the key then it started but as soon as it put it into drive the door locks kept trying to lock every 20/30 seconds then as I got 1/2 mile down the road it defaulted into 1st gear again and the dash started freaking out. I’m hoping someone can point me in the rough direction. Only code I have is P0700 Transmission Control Module (TCM) Requested MIL Illumination (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Test Not Passed Since Power Up, Current DTC Since Power Up.

 

[mikez71]

More than once, I have heard of gauges glitching, and engines dying, due to loose battery cables... (or corroded cables)
Hopefully that's it.. If not, you may need a better scanner to get the TCM codes.. (That P0700 is set by the ECM, despite being TCM related)

 

[07blackeddenali]

More than once, I have heard of gauges glitching, and engines dying, due to loose battery cables... (or corroded cables)
Hopefully that's it.. If not, you may need a better scanner to get the TCM codes.. (That P0700 is set by the ECM, despite being TCM related)

More than once, I have heard of gauges glitching, and engines dying, due to loose battery cables... (or corroded cables)
Hopefully that's it.. If not, you may need a better scanner to get the TCM codes.. (That P0700 is set by the ECM, despite being TCM related)

Cables are good cause I just replaced the battery about a month ago and can rule the scanner out cause I’m using a snap on Zeus

 

[the 18th letter]

Cables are good cause I just replaced the battery about a month ago and can rule the scanner out cause I’m using a snap on Zeus

Check that all your grounds are clean. That’s another issue that can cause strange electrical issues.

 

[Joseph Garcia]

It is most likely an electrical issue. Check your ground connections in the engine bay and on the frame under the truck about where the driver's feet are. Also, as stated above, the battery cable typically rot from the inside out, so a good looking battery cable insulation tells you nothing about what is going on under the insulation. Use an Ohm meter to measure the resistance within the battery cables.

 

[swathdiver]

So I have a ‘07 Yukon Denali 6.2/6l80/awd with approximately 187k and I’ve recently developed an issue that’s a weird one. Couple weeks ago on my way to work the transmission defaulted to 1st gear (only 2.5 miles from my work), let it sit all day and on my way home it was doing the same thing but this time the dash cluster started glitching out going from my speed to 0 and back up again, all my other gauges would stop working also then work and constantly doing this for my drive home. Let it sit over the weekend and has not skipped a beat for the past 1.5/2 weeks I’ve driven it until today where I went to unlock it when I was at the store (drove fine to the gas station then to the store) then all of a sudden as soon as I went to start it the yukon wouldn’t start, cycled the key then it started but as soon as it put it into drive the door locks kept trying to lock every 20/30 seconds then as I got 1/2 mile down the road it defaulted into 1st gear again and the dash started freaking out. I’m hoping someone can point me in the rough direction. Only code I have is P0700 Transmission Control Module (TCM) Requested MIL Illumination (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Test Not Passed Since Power Up, Current DTC Since Power Up.

@NickTransmissions Hey, What do you think of this?

@07blackeddenali How old is your battery and what was its voltage this morning (engine off) and the temperature outside?

 

[07blackeddenali]

@NickTransmissions Hey, What do you think of this?

@07blackeddenali How old is your battery and what was its voltage this morning (engine off) and the temperature outside?

View attachment 446249

Battery is only 2/3 months old and I have no clue lol I’m gonna mess with it tomorrow morning on my day off

 

[NickTransmissions]

Battery is only 2/3 months old and I have no clue lol I’m gonna mess with it tomorrow morning on my day off

Check the transmission plug/case connector, make sure it's actually plugged in to the TEHCM, if you havent resolved the problem already.

Someone else had a similar problem on Silveradosierra.com and the plug wasn't fully connected to the TEHCM.

 

[petethepug]

Hopefully it’s just the simple stuff like a bad electrical connection somewhere. Is the clamp tight holding the battery down? Any major battery / starter cables warmer than others (resistance)?

The fuse box under hood - d/s gets bad contacts under the board sometimes from loose bolts and / or crud.

@NickTransmissions hell of a weekend over there. Take care buddy!

 

[07blackeddenali]

So I checked all the ground I could find under the chassis and this are good, found a couple in the dash that I could access with tearing the dash apart and those are good. As I just went out to start it to go home for lunch it now won’t start, all lights are on the dash, battery has 12.2v but it won’t crank. I’m leaning towards checking the fuse box cause also as stated above it’s a known issue a coworker had to change his on his 2010 Silverado 1500