Medium and Heavy Trucks
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Hi my name is***** post the complete model of your transmission from the ID tag on the transmission and also any fault codes you are getting.
CH is just system check. SM is a system malfunction detected. Click this link for more information, diagrams, and fault codes.
Check the harness and connections for the speed sensor on the transmission for a possible poor connection or corroded damaged wire or connector pin causing a loss of speed signal. Check for fault codes and see what you get for codes. SM means there are codes logged.