My 2 rear's are fused in place; used acetalene torch, had them glowing and still could not get them to turn; gonna have to cut out the mounts and weld in new ones, then install new sensors; likely got the same problem with the fronts; carbon filth the engine builds up bit time on sensors; codes went away for a while after heating them up I guess because I burned off all build-up. they just get fouled badly