Technical Description of OBD-II Trouble Code
Performance Issue with O2 Sensor Reference Voltage for Bank 2 Sensor 1
What is the meaning of P2248?
P2248 is a generic powertrain code that applies to many OBD-II vehicles (1996-newer). This includes vehicles from various manufacturers such as Honda, Ford, Mazda, VW, Mercedes-Benz, Audi, Hyundai, Acura, BMW, etc. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
A stored code P2248 indicates that the powertrain control module (PCM) has detected an electrical voltage outside the normal expected range of performance for the upstream O2 sensor for engine bank two. “Sensor 1” refers to an upstream sensor, and “Bank 2” refers to the bank of the engine that does not contain the number one cylinder.
The PCM monitors the engine air to fuel ratio for each engine bank using data from heated exhaust oxygen sensors. These oxygen sensors have a zirconium dioxide sensing element located in a vented steel housing. The sensing element is connected to wire leads in the oxygen sensor harness connector, which plugs into the controller area network (CAN) that connects to the PCM connector.
Each oxygen sensor is threaded or studded into an exhaust pipe, positioned near the center of the pipe. As exhaust gases flow over the oxygen sensors, they enter through vent holes in the steel housing and swirl around the sensing element. Ambient air is drawn through wire lead cavities in the sensor housing, filling a tiny chamber in the middle. The air in this chamber is heated, causing the oxygen ions to produce voltage that is recognized by the PCM.
Variations in the number of oxygen ions in the ambient air drawn into the O2 sensor, compared to the number of oxygen molecules in the exhaust, cause the oxygen ions inside the sensor to rapidly bounce between platinum layers. These variations in oxygen sensor output voltage indicate changes in exhaust oxygen concentration. The voltage signal from the oxygen sensors is lower when there is more oxygen in the exhaust (lean condition) and higher when there is less oxygen in the exhaust (rich condition).
If the PCM detects an electrical voltage in the oxygen sensor reference voltage circuit that is outside the normal expected range of performance, it will store a code P2248 and may illuminate the malfunction indicator lamp (MIL). In most cases, the MIL will only illuminate after multiple ignition cycles with a failure.
A typical oxygen O2 sensor:
What is the severity of this DTC?
An irregular voltage in the O2 sensor reference voltage circuit can lead to reduced fuel efficiency and engine performance. A code P2248 should be considered severe and addressed promptly.
What are some of the symptoms of the code?
Symptoms of a P2248 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P2248 troubleshooting steps?
To accurately diagnose a code P2248, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and reliable vehicle information.
It may be helpful to search for technical service bulletins (TSB) that match the stored code, vehicle information (year, make, model, and engine), and symptoms. This information can be found in your vehicle information source and may provide a quick solution to the diagnosis.
After connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data, write down the information in case the code is intermittent. Clear the codes and test drive the vehicle until either the code is restored or the PCM enters readiness mode.
If the PCM enters readiness mode, the diagnosis may be more challenging as the code is intermittent. The condition that caused the P2248 code to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.
Use your vehicle information source to obtain connector face views, connector pinout charts, component locator charts, wiring diagrams, and diagnostic flow charts specific to the code and vehicle in question.
Perform a visual inspection of the wiring and connectors related to the code. Repair or replace any wiring that is cut, burned, or damaged.
Use the DVOM to test the O2 sensor voltage at the appropriate connector pin near the sensor. If no voltage is detected, check the system fuses and replace any blown or defective fuses.
If voltage is detected, test the corresponding circuit at the PCM connector. If no voltage is detected there, suspect an open circuit between the sensor and the PCM. If voltage is present at the PCM connector, suspect a defective PCM or PCM programming error.
To test the O2 sensors, start the engine and allow it to reach normal operating temperature. Let the engine idle in neutral or park while observing the oxygen sensor input data on the data stream of the scanner. Narrow the scope of the data stream to include only relevant data for a faster response.
If the oxygen sensors are functioning properly, the voltage on the pre-oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed loop operation. The post sensors will also cycle between 1 and 900 millivolts but will settle at a certain point and remain relatively stable compared to the pre sensors. Oxygen sensors that fail to cycle adequately should be considered defective if the engine is in good working order.
