BUICK/CHEVROLET/HUMMER/GMC/PONTIAC/CADILLAC/SATURN: TECHNICIANS MAY FIND DTCS P0601, P0603, P0604, P062F OR P1621 STORED IN THE TCM AS AN ACTIVE OR A HISTORY CODE. SOME OF THESE DTCS CAN ALSO BE SET IN THE ECM OR FPCM. MAKE SURE THAT YOU KNOW WHICH MODULE (FOR EXAMPLE ECM, FPCM OR TCM) HAS SET THE DTC BEFORE ATTEMPTING TO DIAGNOSE AND REPAIR THIS CONDITION. *PE UPDATED 8/1/11. *PE