Transmission Codes P0842, P0872, P0877**UPDATE**

[donjetman]

07 Denali w/6L80 tranny and has 191k miles, is shifting okay to me, but I borrowed a MAC Tools code reader and found codes for the tranny. So I think its time to replace the TEHCM pressure switches with seals & membranes, Sonnax kit # 124740-70K and Sonnax tool kit # 124740-TL70. @NickTransmissions

 

[NickTransmissions]

07 Denali w/6L80 tranny and has 191k miles, is shifting okay to me, but I borrowed a MAC Tools code reader and found codes for the tranny. So I think its time to replace the TEHCM pressure switch membranes with Sonnax kit # 124740-TL70. @NickTransmissions

Test the pressure switches before spending $$$ on any parts...if they dont pass, TEHCM has to be replaced...I have no clue who that is in the video but if the instructions are clear/accurate, use it....ill be putting out some TEHCM-related videos including switch service, soon...

 

[donjetman]

Sonnax info and video
https://www.sonnax.com/tech_resourc...-gm-6l45-50-80-90-gen-1-6t70-75-transmissions

 

[donjetman]

2007 Yukon Denali with 6L80 with 193k miles.

Got around to replacing the 4 Sonnax pressure switch laminates on the 6L80 TECHM in our Denali 6L80 tranny
.
Removed:
front sway bar
frt drive shaft
trans cross member
exhaust Y-pipe
trans pan & fluid (took a sample for analysis)
filter
6 bolts holding the valve body/TECHM to the trans.

Parts:
6 qts Dexrom6 GM # 88865618
1 trans filter = GM # 24236933
DS metal exhaust seal = GM # 15077362
Pass side exhaust dounut gasket = GM # 15035747
Sonnax 124740-TL30 pressure switch repair kit & tools (ebay)

then
watch this video: about valve body/TECHM removal:

then
watch this video about installing new laminates on TECHM:

then
watch this video about valve body/TECHM install:

You should read @skpyle thread: https://www.tahoeyukonforum.com/thr...-flush-in-2013-escalade-esv-pic-heavy.130110/

I been driving it and its working good, no more 2-3 flare and no codes.

 

[donjetman]

Pics
3 of the 4 laminents were torn/bad.

I change the the atf in the pan (6 qts) every 25k miles
and
the filter and fluid every 50k miles

 

[donjetman]

and more

 

[Foggy]

What exactly are the "laminents" you speak of ?? (which picture maybe)
and what do you think they do ???
Did this fix your issues ???

 

[NickTransmissions]

What exactly are the "laminents" you speak of ?? (which picture maybe)
and what do you think they do ???
Did this fix your issues ???

He seems to be referring to the TEHCM pressure switch diaphragms which can get brittle and crack when the trans runs hot for prolonged periods. The diaphrams serve as an intermediary between the switches themselves and environment inside the trans...When they crack or get distorted, the switches underneath have trouble communicating information to the rest of the TEHCM and ECM and shifting/drivability issues result. Its generally a good idea to service them and their respective seals every 70k or so as a preventative measure.

Transgo and a few others make these service kits. They do not fix malfunctioning pressure switches; replacing the TEHCM is the only cure for that type of problem.