My 2002 MC with 90,000 mi. shows a p0136 fault code which pertains to an
O2 sensor circuit (bank1 sensor 2). Should I consider this an indicator to change the sensor? Should I consider changing out both O2 sensors? I
understand they don't last much past 100k. Any tips would be appreciated.

 

Generally folks have had issues with the NON OEM sensors...so find a OEM one....sounds like it is the POST cat sensor....here are a few more of the O2 specific codes...

P0130 O2 Sensor Circuit
P0131 O2 Sensor Circuit Low Voltage
P0132 O2 Sensor Circuit High Voltage
P0133 O2 Sensor Circuit Slow Response
P0134 O2 Sensor Circuit No Activity Detected
P0135 O2 Sensor Heater Circuit
P0136 O2 Sensor Circuit
P0137 O2 Sensor Circuit Low Voltage
P0138 O2 Sensor Circuit High Voltage
P0139 O2 Sensor Circuit Slow Response
P0140 O2 Sensor Circuit No Activity Detected
P0141 O2 Sensor Heater Circuit
P0142 O2 Sensor Circuit
P0143 O2 Sensor Circuit Low Voltage
P0144 O2 Sensor Circuit High Voltage
P0145 O2 Sensor Circuit Slow Response
P0146 O2 Sensor Circuit No Activity Detected
P0147 O2 Sensor Heater Circuit
P0148 Fuel Delivery Error
P0149 Fuel Timing Error
P0150 O2 Sensor Circuit
P0151 O2 Sensor Circuit Low Voltage
P0152 O2 Sensor Circuit High Voltage
P0153 O2 Sensor Circuit Slow Response
P0154 O2 Sensor Circuit No Activity Detected
P0155 O2 Sensor Heater Circuit
P0156 O2 Sensor Circuit
P0157 O2 Sensor Circuit Low Voltage
P0158 O2 Sensor Circuit High Voltage
P0159 O2 Sensor Circuit Slow Response
P0160 O2 Sensor Circuit No Activity Detected
P0161 O2 Sensor Heater Circuit
P0162 O2 Sensor Circuit
P0163 O2 Sensor Circuit Low Voltage
P0164 O2 Sensor Circuit High Voltage
P0165 O2 Sensor Circuit Slow Response
P0166 O2 Sensor Circuit No Activity Detected
P0167 O2 Sensor Heater Circuit