I was checking the o2 sensors and while checking the ground wires with my multimeter, I got three dings when checking the female end connector for the passenger side o2 sensor. Now shouldnt there only be two ground wires for both the sensors? I only get two dings when checking the driver side o2 connector. And if I'm getting a bad ground wire on the passenger side connector would that be causing the rich condition?

 

LTFT indicates it's running rich, and the O2 sensor readings confirm it. O2 sensor voltage is supposed to cycle up and down between 0 and .9VDC, perfectly normal. In post #2 I asked about fuel pressure and leakdown, your response was, "The fuel pressure is also fine, checked that when checking the lines for clogs." What are the readings using this procedure:
1) Key ON, engine OFF, fuel pump running?
2) What is the pressure 10 minutes after the pump shuts off?

 

Im curious if you were able to resolve your p0172 and p0175 DTCs. My 1999 blazer is throwing the same codes. Any update would definetly be appreciated.