1997 gmc 4l60e
The 1-2 accumulator is used during the 1->2 shift.
As mentioned, the most likely cause is the 1-2 Solenoid is disconnected, either because you didn't fully plug it in, its electrical tabs got broken or the new harness is defective.
As mentioned, the most likely cause is the 1-2 Solenoid is disconnected, either because you didn't fully plug it in, its electrical tabs got broken or the new harness is defective.








