What Does P0146 Mean?
The O2 sensor on Bank 1, Sensor 3 is showing no activity — its voltage output is stuck and not switching between rich and lean as expected. The PCM has determined the sensor signal is flatlined, indicating the sensor is not responding to changes in exhaust oxygen content. The driver may not notice any driveability symptoms, but the MIL will illuminate and the vehicle will fail emissions testing.
Common Causes
45%
Failed O2 sensor (Bank 1 Sensor 3) with no voltage output or internal open circuit
25%
Open or shorted wiring in the O2 sensor signal circuit
15%
O2 sensor heater failure preventing the sensor from reaching operating temperature
10%
Severe exhaust leak upstream of the sensor diluting exhaust gases
5%
PCM driver circuit fault or poor ground connection
Diagnostic Steps
1
Monitor Bank 1 Sensor 3 voltage on live data — a stuck reading near 0.45V (bias voltage) indicates an open circuit or dead sensor; stuck near 0V or 1V suggests a short to ground or power.
2
Disconnect the O2 sensor connector and check for 0.45V reference bias on the PCM side of the harness with the key on, engine off.
3
Measure the sensor's heater resistance at the connector (typically 2-25 ohms); an open reading (OL) confirms a heater failure preventing warm-up.
4
Inspect the wiring harness for heat damage, rodent chew, corroded pins, or water intrusion at the connector.
5
With the sensor reconnected and engine at operating temperature, briefly create a rich condition (propane enrichment) — the sensor should respond above 0.7V if functional.
Estimated Repair Cost
$100 - $300
Parts + labor, varies by vehicle and location
The O2 sensor on Bank 1, Sensor 3 is showing no activity — its voltage output is stuck and not switching between rich and lean as expected. The PCM has determined the sensor signal is flatlined, indicating the sensor is not responding to changes in exhaust oxygen content. The driver may not notice a...
The most common cause of P0146 (02 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)) is: Failed O2 sensor (Bank 1 Sensor 3) with no voltage output or internal open circuit
Typical repair costs for P0146 range from $100 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. Bank 1 Sensor 3 is a downstream monitoring sensor and does not directly control fuel delivery. The vehicle will not pass emissions testing and the check engine light will remain on.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0146 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions / Exhaust System
Difficulty
Type
Generic (SAE)
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