92 MX3 trans slipping w/code 6- speed sensor

[Flash]

Trans slips a little in first, but with hold button in first gear it works ok. Pulled code 6 from the ECM. The speedometer works ok. Iv'e found the turbine speed sensor, is the speed sensor in the insturment cluster? I pulled the cluster but did not see one. Can anyone give me the diagnosis tree for a code six. The vehicle is an MX3 with a 1.6 lit. build date of 9/1991.
Thanks