P0796 Replacing valve body and techm

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Shawgeorge11

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2009 GMC Yukon 5.3 V8 2wd 6L80 124,000 miles

I had a heater hose bust on me a few weeks ago, coolant leaked pretty good within engine bay, mostly towards passenger side towards firewall. I replaced heater hose and refilled the coolant. Rpm's would go up and down a little when driving at a constant speed, no check engine light. I notice the air filter where it connects to the throttle body was a little loose (pretty sure that was my fault, just forgot to tighten the clamp). A few days later I get code 700 and 1516. I replace tps sensor and pigtail connector as well as maf sensor and its pigtail connector. 1516 goes away, but 700 stayed and 2723 popped up. Shifting becomes erratic, with transmission 'feeling' like it is slipping, but I can't tell if it is mechanical or electrical. A few days later 2723 goes away but then I get 796. That's where I'm at today. Not driving the car anymore. ATF was replaced around 100k. Transmission never had any issues beforehand. The fluid is of a brownish red color with a bit of a bad smell, but not too bad.

I have had two mechanics look at it. One thought I needed to replace whole tranny. The other did not agree based on the fact that the car still drives forward and reverse and there are no other codes. They both got code 796 on their scanners, but we have not checked the pan yet.

I know I should have at least checked the pan first before ordering parts, but I am pressed for time and also just hoping its the tcm/techm which is where said stuck solenoid is located.
I've ordered the new VB and pre programmed techm from Street Smart.

Anyone out there with experiences replacing techms or get code 796 and how did you get it fixed? God bless and thank you in advance!
 

swathdiver

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You can first try to rebuild your TECHM, that's basically what the troubleshooting guide says to do for P0796.

It can be done on the kitchen table and several guys on here have done it and they have posted lots of pictures but it is pretty intuitive.



 

rockola1971

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I guess it all depends on your budget and whether you want to gamble how long the tranny is going to lastby just DIY or have a shop take care of the stuck pressure switch. But none of that changes the fact that "fluid is of a brownish red color with a bit of a bad smell, but not too bad.". That brownish color and that bad smell means you burnt your tranny fluid and that was caused by slipping clutches. The damage is done and it will go downhill from here. Tranny may last another year or so or may only last weeks.
 

Just Fishing

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pressure switches are common.
There are a few really good youtube videos covering how to rebuild them.
buy the sonnax tool to help with the laminate install and the seal install.
It's worth every penny, the tool runs like $40 and comes with a set of laminates and seals.
 

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