1998 GMC Sonoma Q&A
1998 GMC Sonoma Question: trouble code "transmission module unstable"
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. - Oakman
code checker used shows a code "1870" trans module unstable, have cleared it several times, comes on after 40-75 miles. What are possible fixes? Where is transmission module?