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P0163 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


DTC codes are alphanumeric designations used by the vehicle’s On-Board Diagnostic (OBD) system to pinpoint specific issues within various components. P0163 is a DPC that relates to the O2 sensor circuit located in Bank 2, Sensor 3 and is also referred to as an external O2 sensor. This sensor is an essential element to monitor the oxygen content in exhaust gases after they are discharged into a catalyst converter.


P0163 indicates that there is an issue with the reaction from the Downside O2 Sensor on Bank 2. In particular, the sensor’s slow response has been detected, which means that it is taking longer than expected to transition between rich and poor conditions. Some factors affecting the ability of a sensor to detect precise readings may contribute to this discrepancy.


  • Defective Oxygen Sensor: One of the main root causes of the P0163 code is a deficient downstream O2 sensor. Slow reaction times can be caused over time by polluted or worn-out sensors.
  • Problems with the wire or connections: Corroded or damaged wiring and connectors connected to the downstream O2 sensor might obstruct the signal’s path and impair the sensor’s responsiveness.
  • Exhaust System Leaks: Any leaks in the exhaust system close to the O2 sensor’s downstream location might inject misleading air into the system and affect the sensor’s response.


  • Check Engine Light Illumination: The Check Engine Light illumination on the dashboard of the car is the P0163 code’s most obvious symptom.
  • Lower Fuel Efficiency: Inadequate fuel mixture management caused by a downstream O2 sensor that is faulty and has a poor reaction time might result in lower fuel economy.
  • Problems with engine performance: Due to inaccurate sensor readings, your engine may have less power, a rough idle, or trouble starting.


The P0163 code has to be diagnosed using a methodical process:

  • OBD-II Scanner: A skilled mechanic will access the vehicle’s Engine Control Module (ECM) with an OBD-II scanner to extract the recorded DTCs.
  • Visual Inspection: The downstream O2 sensor, its cabling, and its connections will be visually inspected by the technician for any obvious flaws or damage.
  • Sensor Testing: To evaluate the downstream O2 sensor’s reaction time under varied exhaust circumstances, specialized diagnostic equipment may be employed.
  • Cross-checking: The technician can validate the problem by comparing the upstream O2 sensor readings and the actual sensor response time to the predicted values.

Common mistakes

  • Replace the O2 sensor without confirmation of the root cause, since it is possible that further factors such as electrical problems or leakages into an exhaust system may contribute to this delay in response. 
  • Missing the possibility of detecting related trouble codes, which may contribute further insight into the problem.

How serious is this?

While the P0163 code may not result in immediate and serious drivability problems, it should not be ignored. If the downstream O2 sensor is malfunctioning, with slower response times, an increase in emissions and a reduction in fuel efficiency may result, which will pose more serious problems over time.

What repairs can fix the code?

repair manuals

  • O2 Sensor Replacement: If the downstream O2 sensor is found to be malfunctioning or to have sluggish reaction times, the problem can be solved by replacing it with a fresh, high-quality sensor.
  • Repairing wire or connections: Correct signal transmission and responsiveness can be restored by addressing any corroded, damaged, or attached wire and connections.
  • Repairing Exhaust System Leaks: The reaction time of the downstream O2 sensor can be enhanced by fixing any leaks in the exhaust system close by.

Related codes

  • P0149: O2 Sensor Circuit Slow Response (Bank 2, Sensor 3)
  • P0150: O2 Sensor Circuit (Bank 2, Sensor 1)


A DTC code of P0163 is given for a downstream O2 sensor in Bank 2, indicating that it responds slowly. Owners and mechanics are empowered to take suitable action by knowing what is going on with this code, the causes of it, symptoms, or possible repairs. In order to maintain optimum engine performance, fuel efficiency, and emission control, timely diagnosis and resolution will be helpful.

If you have encountered P0163 codes or suspect that O2 sensor problems are occurring, seeking the assistance of an experienced technician is essential in order to effectively solve this problem and ensure your vehicle runs smoothly and efficiently.

P0163 Code – What Does It Mean & How To Fix It