Home >> GMC >> 2021 >> Acadia AT4 >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission - 9T50 (M3H), 9T60 (M3G) Or 9T65 (M3W) - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC P18A2 or P18A4 >> Diagnostic Fault Information