Technical Definition:

O2 Circuit Low Voltage (Bank 2, Sensor 3)

Technical Description:

The code refers to a fault in one of the post-catalyst O2 sensors on Bank 2. This oxygen sensor is used for a specific purpose. This is it in a nutshell: The Catalytic Converter is used to help control emissions, to “clean up” the exhaust gasses. The PCM (Powertrain Control Module) uses the signal from post catalyst heated oxygen sensors to monitor the catalyst’s efficiency by comparing it to the O2 sensors in front of the catalyst. If the PCM sees little or no difference between the exhaust quality in post- and pre- catalyst sensors then it knows that the catalyst is not working properly.

Possible Causes:

• Air leaks in exhaust in front of O2 sensor giving false reading
• Engine running excessively lean
• O2 sensor connector damaged/corroded
• O2 sensor signal circuit is shorted to ground
• O2 sensor ground circuit is open
• O2 sensor has failed (it may be contaminated with fuel or coolant)
• PCM has failed

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Engine performance issues
• Engine running rough
• Engine running rich (only if PCM is trying to add fuel to compensate for low O2 sensor voltage reading)
• Engine running lean (only if vacuum leak is large enough that PCM can’t compensate by adding fuel)
• Poor idle

O2 Sensor Circuit Low Voltage Bank 2 Sensor 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust