P0145 OBD-II Trouble Code: O2 Sensor Circuit Slow Response (Bank 1, Sensor 3)

Check Engine Light

P0145 code definition

O2 Sensor Circuit Slow Response (Bank 1 Sensor 3)

What the P0145 code means

P0145 is the OBD-II generic code indicating that the O2 sensor for bank 1 sensor 3 fails to have a voltage drop to below .2 volts for 7 seconds during a deceleration fuel cut off. The Engine Control Module (ECM) has determined the sensor response to be too slow.

What causes the P0145 code?

  • The ECM cuts all fuel to the engine during deceleration and the O2 sensors all should respond with a voltage output below .2 volts showing the exhaust stream is higher in oxygen content with no fuel.

  • The code is set if the O2 sensor for bank 1 sensor 3 does not respond to the fuel cutoff for around 7 seconds.

  • The O2 sensor may be defective or the fuel system injector is leaking.

What are the symptoms of the P0145 code?

  • The engine may stall or run rough on deceleration; fuel is getting in the engine when the ECM has cut the fuel.

  • The Check Engine Light will come on once the ECM sees a problem with the O2 sensor.

  • The engine may hesitate upon acceleration after a deceleration phase if the engine is loaded up with fuel.

How does a mechanic diagnose the P0145 code?

  • Scans codes and documents freeze frame data for the O2 sensor

  • Monitors the O2 sensor data to see if the voltage is dropping to below .2 volts during deceleration for all the O2 sensors

  • Checks the fuel injection system for leaking injectors if all the O2 sensors indicate voltages above .2 volts on deceleration

  • Checks the engine fuel pressure for a leaking fuel injector or fuel pressure regulator

  • Checks the O2 sensor for contamination with coolant or oil

  • Checks the O2 sensor harness for water contamination

  • Follows the manufacturer's specific pinpoint tests for further diagnosis

Common mistakes when diagnosing the P0145 code?

Follow these simple guidelines to prevent mistakes:

  • Check the complete fuel system for other problems before replacing any O2 sensor.

  • Check the fuel injection system for any leaking injectors, or a pressure regulator that is causing fuel fouled O2 sensors and catalyst.

  • Repair oil or coolant leaks onto the O2 sensor before replacing the sensor to prevent contaminating the new sensor.

How serious is the P0145 code?

  • The ECM cannot control the fuel shut off if the fuel injectors are leaking. This will lead to excessive fuel consumption.

  • Excessive fuel in the exhaust stream on deceleration can cause the engine to stall or run rough.

  • A failed sensor will not affect the ECM’s control of the air-fuel ratio for the engine.

What repairs can fix the P0145 code?

Additional comments for consideration regarding the P0145 code

The slow response of an O2 sensor may be due to a sensor that is just getting old and over time may get contaminated with time with carbon and other contaminants that deteriorate the sensors ability to respond to the exhaust changes.

Need help with a P0145 code?

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