I recently installed a 6liter in a v6 99 model truck. I had a donor truck and swapped motor, tranny, and pcm with harness. Had a check engine light that had me chasing o2 sensors. I bought 2 new GM units(117$ a pc.) and the code is still coming on. My tuner and I scanned and data logged. The o2's are working but are very slow moving. It's like watching a data log from a normal tune in slow motion.(the o2 mv's) All other parameters are in good shape.Any ideas?

 

Any ideas out there?

 

Do you have power to them? If you don't have 12 volt power to them they will switch very slow. They need to have power to heat up.