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trouble code "transmission module unstable" on 1998 GMC Sonoma

Trouble code "transmission module unstable". What are possible fixes? Where is transmission module?

Asked by for the 1998 GMC Sonoma
The transmission on your 1998 GMC Sonoma is controlled by the PCM (Powertrain Control Module) The PCM combines the engine and transmission control modules. I have been a GM tech for over 25 years and I have never hear of a code description of "transmission module unstable" If you could send the code number Pxxxx that would be a big help.
The code checker I used only shows 1870, the book supplied with checker has "trans module unstable" as description. Thanks.