Technical Description of OBD-II Trouble Code
The O2 Sensor Reference Voltage Circuit for Bank 2 Sensor 1 is too high.
What is the meaning of P2250?
P2250 is a generic powertrain code that applies to many OBD-II vehicles (1996-newer), including Honda, Ford, Mazda, VW, Mercedes-Benz, Audi, Hyundai, Acura, BMW, etc. The exact repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
A stored code P2250 indicates that the powertrain control module (PCM) has detected an excessive reference voltage 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 input from heated exhaust oxygen sensors. These sensors consist of 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) and 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. The oxygen ions in the sensor bounce between platinum layers, causing variations in oxygen sensor output voltage. The PCM interprets these voltage variations as changes in exhaust oxygen concentration.
If the PCM detects a high electrical value in the oxygen sensor reference voltage, it stores a code P2250 and may illuminate the malfunction indicator lamp (MIL). Most vehicles require multiple ignition cycles with a failure for the MIL to illuminate.
A typical oxygen O2 sensor:
What is the severity of this DTC?
An excessive voltage in the O2 sensor reference voltage circuit can lead to reduced fuel efficiency and engine performance. A code P2250 should be considered severe and addressed promptly.
What are some of the symptoms of the code?
Symptoms of a P2250 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P2250 troubleshooting steps?
To accurately diagnose a code P2250, 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, 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 because the code is intermittent. The condition that caused the P2250 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 source of vehicle information 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.
Inspect the related wiring and connectors visually. 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 pertinent data for a faster response.
If the oxygen sensors are functioning normally, the voltage on pre-oxygen sensors will cycle continuously between 1 and 900 millivolts once the PCM enters closed loop operation. 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.
