Trying to tune and have issue with readings...trying to trouble shoot issue with short term fuel on B2...swapped o2 sensors and high reading was same on B2 (guess eliminated sensor as the problem) Did wiring check from harness conn to PCM pins all ring good and correct. Have high reading on B2 (99.2% see pic)) with engine off, o2 sensor disconnected. When running o2 readings on b1 0.445v steady b2 - 0.45 - 0.85v bouncing. The PCM is a GM truck 98-2000, eng Ls3 variant, truck harness, DBW



. Not sure what this means, any advice appreciated.

 

The 99.2% value shown for the secondary O2 sensor short term fuel trim are indicators that the sensors are not used for the short term fuel trim calculation. So no need to worry about the seemingly high numbers.