'01 Ranger Check engine light HELP

i have an 01' ranger 2.3L 5 speed. it has about 85,000 miles. i just had the clutch master cylender replaced. about 2 weeks after the
check engine light came on. brought it by auto zone to have it checked and they said that it had something to do with the transmission speed. the only odd thing i notice about it is the ideling seems alittle different. any suggestions?
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