Check with your dealer about the tcm (transmission control module) recall. GM sent out a recall to dealers telling them to reprogram the tcm to remedy the p0700 codes. I was getting these codes too until I took my truck in had it reprogrammed and have had no problems since. By the way I drive an 07 duramax lbz. Hope this helps
Let us know how that goes.
I always thought that the computer on the trans had to have some learning time of the extra power our tunes give to get the engine and trans power in sinc.
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