96 blazer 02. Sensor locations
 

Hello all

I plugged my obd 2 reader in 96 blazer and its throwing o2 sensor codes. The codes are p0147,p0135,p0146,p0154,p0155,p0141. I do think the 02 sensors are bad and need to be replaced. I am not getting a check engine light on at all. I do think these codes fall under the o2 sensor area.

Each of these codes should result in a CEL if they are current codes (i.e. not 'pending' or 'history'). Does your scantool list whether the code is pending, current/set, or history?

P0147 - O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 3)
P0135 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
P0146 - O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)
P0154 - O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
P0155 - O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)

Given that there is a code listed for each of the sensor heater circuits, I would venture a guess that there is something wrong with the circuit that provides power & ground to the heaters. I would start by disconnecting all of the O2 sensors & testing for power/ground at each connector. I couldn't find a diagram specific to your year, but on the 98+ trucks +12V is a pink wire, ground is a black wire, and the sensor high/low lines are purple & tan (with varying stripes). The +12V wire should have power in start & run.

I'm not sure what might be going on with the no activity codes, but I do know that O2 sensors need to be hot to properly read so I would start with getting the heaters functioning.