Technical Description of OBD-II Trouble Code
High Circuit in Bank 1 NOx Sensor
What does that signify?
This is a generic diagnostic trouble code (DTC) for powertrain and is commonly found in OBD-II vehicles. This can apply to various vehicle brands such as Ford, Mercedes Benz, BMW, VW, Audi, Chevrolet, GMC, Dodge, Ram, Sprinter, and more. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
In general, diesel-fueled engines produce higher levels of particulate matter (PM) and Nitrogen Oxide (NOx) emissions compared to gasoline engines.
As vehicle emission standards have evolved, engineers have been developing methods to reduce atmospheric emissions in order to comply with and exceed emission requirements set by state/provincial laws.
The Engine Control Module (ECM) constantly monitors numerous sensors to ensure the efficiency, reliability, and functionality of the engine. Additionally, it actively monitors emissions to minimize the release of hydrocarbons into the atmosphere. The NOx sensor is used by the ECM to measure nitrogen oxide levels in the exhaust and determine the amount of hydrocarbons being emitted. NOx is a primary particulate matter produced by diesel engines. The ECM continuously monitors this sensor and adjusts the system accordingly.
It is important to note that the exhaust of a diesel engine is a highly contaminated area. The soot produced by a diesel vehicle can accumulate on sensors and switches within the exhaust, potentially affecting their performance. This becomes particularly significant due to the unique characteristics of the soot. If the sensor becomes clogged with debris, it may not accurately measure the values required by the ECM to adjust the EVAP (Evaporative Emissions) system in accordance with federal/state/provincial laws. In some cases, aftermarket sensors are used to comply with local emission standards when traveling between states with different regulations.
The ECM triggers the P2203 code and related codes (P2200, P2201, P2202, and P2204) when it detects a fault in the NOx sensors or their circuits. While my experience with this code is limited, it is likely that mechanical issues are often the cause, especially considering the conditions mentioned earlier.
The P2203 code is set when the ECM detects a high voltage condition in the bank #1 NOx sensor or circuit.
Note: On engines with multiple banks of cylinders (e.g. V6, V8), bank 1 refers to the side of the engine that contains the #1 cylinder. Therefore, the NOx sensor is located in the exhaust of that bank. Refer to your service manual for specific information regarding your make, model, and powertrain. The service manual is the primary resource for identifying the specific sensor among the many possibilities. Similar distinctions are made for O2 (oxygen) sensors.
Here is an example of a NOx sensor for GM vehicles:
What is the severity of this DTC?
In most cases, emission-related codes are relatively low on the severity scale, especially when compared to potential hazards in other vehicle systems such as steering, suspension, and brakes. If you have more pressing issues to address, you can prioritize those over this code. However, it is important to address any electrical faults with a sense of urgency.
What are some of the symptoms of the code?
Some symptoms of a P2203 trouble code may include:
What are some of the common causes of the code?
The causes of this P2203 fuel trim code may include:
What are some P2203 troubleshooting steps?
Begin by visually inspecting the sensor and its harness. Sometimes, external elements can cause faults in our vehicles. I have seen sensors like these damaged by rocks, curbs, snow, and ice, so ensure that the sensor is intact and in good condition. Keep in mind that some harnesses may be located close to the exhaust, which increases the risk of wires becoming burnt or melted, leading to various problems.
TIP: Allow the engine to cool before working near the exhaust.
Clean the sensor. It is important to note that any sensor mounted in the exhaust undergoes numerous heating and cooling cycles. As a result, they may expand and contract, potentially causing them to become stuck in the sensor “bung” (thread hole) on the exhaust.
If this is the case, you may need to apply heat to the threads, but avoid applying heat directly to the sensor as it may damage the NOx sensor. If you have never used heat to assist in loosening nuts or bolts, I would advise against starting with this method. If you have any doubts about your skills or abilities, it is always best to take your vehicle to a reputable service station.
