P0146 code definition
O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)
What the P0146 code means
P0146 is the OBD-II generic code indicating the O2 sensor for bank 1 sensor 3 fails to have a voltage change from between 410-490 mV for more than 74 seconds.
What causes the P0146 code?
The O2 sensor for bank 1 sensor 3 does not respond to the fuel cutoff or fuel enrichment by the Engine Control Module (ECM) for more than 74 seconds indicating no response to enrichment.
The O2 sensor and mass airflow sensor comparison is misinterpreted by the ECM.
The mass airflow sensor is not indicating airflow correctly due to contamination or a defective sensor.
What are the symptoms of the P0146 code?
The Check Engine Light will come on indicating a problem.
There may be no drive symptoms since the sensor is not used as an input for the engine's fuel/air ratio.
If the problem is not isolated to just this code and other codes are retrieved, then drive symptoms would be for that code and not P0146.
How does a mechanic diagnose the P0146 code?
Scans codes and document freeze frame data
Monitors the O2 sensor data to see if the voltage is moving above or below 410-490 mV
Monitors the mass airflow sensor data for responses to throttle changes per specifications
Follows the manufacturer's specific pinpoint tests for further diagnosis of the code
Common mistakes when diagnosing the P0146 code
Follow these simple guidelines to prevent mistakes:
Do not assume the O2 sensor is bad by replacing a good part; do a complete pinpoint test.
Check the mass airflow sensor for proper operation and contaminations from dirt, oil and debris from a compromised air filter or an oil bath type filter.
How serious is the P0146 code?
This code can be due to problems with the mass airflow sensor, which is needed to calculate the proper amount of air entering the engine. Along with the O2 sensors, the failure of any of these components will cause the ECM to miscalculate the air going into the engine.
The ECM loses control or gets the wrong input from sensors like the mass airflow sensor or the O2 sensor if they are within specification, but incorrect.
The O2 sensor by itself will not cause a drive symptom, but will cause a failure during an emissions test.
What repairs can fix the P0146 code?
Replacing the O2 sensor if it does not respond
Testing the mass airflow sensor for the proper readings per specifications when the engine is off and running
Replacing the O2 sensor or mass airflow sensor if contaminated or fails tests
Cleaning out the mass airflow sensor to see if readings change
Disconnecting the O2 sensor to see if the voltage goes to zero to check the wiring to the sensor
Additional comments for consideration regarding the P0146 code
Check and clean the mass airflow sensor to make sure that it is not causing the O2 sensor input to be incorrect.
Need help with a P0146 code?
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This article originally appeared on YourMechanic.com as P0146 OBD-II Trouble Code: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 3) and was authored by Jay Safford.