I have a 2000 Blazer LS, 4.3 V6 with 97,000 Miles. I recently got the code P0171( system too lean Bank 1 ) So I replaced all 3 Oxygen sensors with Bosch 4 Wire Ready Wired Sensors. The New sensors have 2 White wires for the Heater, 1 Black wire for the Signal and 1 Grey wire for the Ground. The original Sensors have 2 Dark Brown wires for the Heater, 1 Purple wire for the Signal and 1 Light brown wire for the ground. I double checked the wiring on the new sensors and they are correct. I unhooked the battery for 4 hours, Drove the blazer and now I have 6 codes that repeat when I disconnect the battery or erase the codes. They are P0146 ( o2 Circuit no activity detected on Bank 1 Sensor 3 ) P0154 ( o2 Circuit no activity detected on Bank 2 Sensor 1 ) and P0155 ( o2 Heater circuit Bank 2 Sensor 1 ). I checked the 20 Amp fuse for the O2 system and it is OK. Any suggestions on where I should go next? Thanks

 

P0146 - HO2S Circuit Insufficient Activity Bank 1 Sensor 3
P0154 - HO2S Circuit High Voltage Bank 2 Sensor 1
P0155 - Heated Oxygen Sensor Heater Circuit (bank 2, sensor 1)
P0171 - Fuel Trim System Lean Bank 1

Look for similarities in the wiring schematics between the indicated codes..

I hope this problem is not caused by your choice of O2 sensor. GM products do not tend to like Bosch O2 sensors over the long haul.

Why would you replace all 3 of the sensors anyway? Only the ones closest to the engine have anything to do with fuel delivery. And even at that, you need to determine what is the cause of the lean condition. Chances are, the O2 sensor is not at fault.