2004 Chevy Impala 2004 CHEVROLET IMPALA SS

U1040 isnt a code for wheel sensors or pump, it's a communication problem between the brake module and the rest or the modules, try inspecting the plug at the brake module. It's on left rear (drivers) side on ABS hydraulic modulator. Look for water intrusion, or bent or pushed out pins...broken wires! Check fuses! Under the hood there is a fuse box as well as in the car, look for all that refer to ABS or EBCM.