1995w4.3 obd1.5 0172 Troubleshooting nightmare.
 

I have replaced everything in the emissions system including Spider assembly... The code reader I have access too is funny because the year/obd1.5 ... I am trying to figure out the Rich Condition. I guess my first question for now to keep it simple and give me ideas is:::: This model only has TWO O2 sensors. I precat where the left and right exhaust meet... One post CAT... HOW does the computer read Right BAnk Rich with only ONE O2 sensor.... I am Confused and speculate but have yet to find out exactly how the PCM?ECM knows??? I love my Rig but it has become a constant headache and it's my only vehicle.

hi. I would start by clearing the codes and then 1) see if it comes back, and 2)unplug one of the O2 sensors and see what the code reads. I suspect that the upstream sensor is bank 1 (left) and the downstream sensor is bank 2 (right). I could be wrong. next check for any vacuum leaks. more o2 in the system will give you a rich reading. are you seeing any black smoke from the tailpipe? too much fuel. check for fuel pressure to high or leaking injector. check the plugs for a black sooty one, not firing. bad plug or wire. a faulty or out of spec MAF sensor can cause this code also. good luck.