Technical Description of OBD-II Trouble Code
02 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)
What is the meaning of this code?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The catalytic converter is responsible for controlling emissions. The o2 sensor on Bank 1, position 3 is located after the converter and monitors the efficiency of the catalyst. The Powertrain Control Module (PCM) compares the post-cat o2 sensor to the pre-cat o2 sensors to perform this function.
The o2 sensor is a four-wire sensor. The PCM supplies a reference voltage of approximately half a volt to the sensor and also provides a sensor ground and 12 volts for the heater element. The fourth wire serves as a ground for the heater element, which helps the sensor warm up faster and allows the engine to reach closed loop sooner.
The sensor adjusts the supplied reference voltage based on the oxygen content of the exhaust. Oxygen sensors can vary their voltage output between 0.1 volts and 0.9 volts. A lean exhaust produces low voltage, causing the supplied 0.45 volts to drop. A rich exhaust produces high voltage, causing the supplied 0.45 volts to increase. Pre-catalyst o2 sensors rapidly switch between low and high voltage, while a post-cat o2 sensor may switch slower and not vary as much, which is considered normal. If the sensor does not respond as expected or there are too few voltage switches within a given time period, the P0146 code may be set.
Symptoms
The symptoms of a P0146 DTC may include:
Causes
Potential causes of a P0146 code include:
Possible Solutions
1. Start the engine and allow it to reach operating temperature. Use a scan tool to observe the voltage reading of the Bank 1 position 3 o2 sensor. If the voltage does not fluctuate between 0.1 and 0.9 volts, increase the engine RPM to a fast idle and recheck the sensor voltage reading. If it starts switching at this point, the sensor may be sluggish or intermittently going dormant. It would be advisable to replace the sensor in this case.
Visually inspect the o2 sensor for any contaminants. If it appears to be contaminated with coolant or oil, it should be replaced.
a. If the sensor still does not respond after increasing the engine RPM, turn off the engine and unplug the o2 sensor in position 1/3. With the key on and the engine off, check for battery voltage and ground to the o2 sensor heater element. If there is no battery voltage to the heater element, it can cause the o2 sensor to go dormant and not switch properly, resulting in a P0146 code. Therefore, it is important to diagnose this problem first (there will usually be other codes present).
b. If there is power and ground to the heater element, check for the presence of sensor ground. If it is present, connect a jumper wire between the sensor ground and signal wire. The voltage reading of the 1/3 o2 sensor should now be low. If it is, replace the Bank 1 position 3 o2 sensor.
c. If, after connecting the jumper wire, the o2 sensor reading remains stuck, check for wiring problems, harness contact with exhaust components, or broken connectors. Repair any issues found and then recheck.
d. If no wiring problems are found and the o2 sensor reading on the scan tool does not change after installing the jumper wire, recheck at the PCM connector. If there is still no change, the PCM may be at fault.
