Technical Description of OBD-II Trouble Code
High Bank 2 Control Circuit for NOx Sensor Heater
What does that signify?
This is a generic diagnostic trouble code (DTC) for powertrain and is commonly found in OBD-II vehicles. It can be applicable to various vehicle makes such as BMW, Dodge, Ram, Audi, Cummins, etc.
NOx (Nitrogen Oxide) sensors are primarily used in diesel engines for emission systems. Their main function is to detect NOx levels in the exhaust after combustion in the combustion chamber. The system then recycles these emissions using different methods. Due to the harsh environment, these sensors are made of a combination of ceramic and a specific type of zirconia.
One of the negative impacts of releasing NOx into the atmosphere is the potential for smog and acid rain. Failure to monitor and adjust NOx levels properly can have a significant effect on the air we breathe and the environment. The Engine Control Module (ECM) continuously monitors the NOx sensors to ensure acceptable emission levels in the vehicle’s exhaust. The NOx sensor heater control circuit is responsible for preheating the sensor. This helps to expedite the sensor’s warm-up time and bring it to operating temperature efficiently, without relying solely on exhaust temperatures.
When it comes to the P2220 code and related codes, it means that the NOx sensor heater control circuit has malfunctioned and the ECM has detected this issue. For reference, Bank 1 refers to the side where the number 1 cylinder is located, while Bank 2 refers to the other side. In the case of a straight 6 or 4-cylinder engine with only one head, it may have a two-sided downpipe/manifold. Always consult the service manual for location designations, as this is crucial for the diagnostic process.
P2220 is a generic trouble code that indicates a “NOx Sensor Heater Control Circuit High Bank 2” issue. It appears when the ECM detects a higher than expected voltage condition in the NOx sensor heater control circuit on bank 2.
Diesel engines, in particular, generate a significant amount of heat, so it is important to allow the system to cool before working on any exhaust system components.
An example of a NOx sensor (in this case, for GM vehicles):
What is the severity of this DTC?
This DTC has a medium severity level, as faults related to emissions can have a significant impact on the environment. However, sometimes there may not be any noticeable symptoms, but leaving the issue unattended can still have repercussions.
What are some of the symptoms of the code?
Symptoms of a P2220 diagnostic code may include:
What are some of the common causes of the code?
Causes for this P2220 code may include:
What are some diagnostic and troubleshooting steps for P2220?
The first step in troubleshooting any malfunction is to research the Technical Service Bulletins (TSB) for known issues with the specific vehicle.
Advanced diagnostic steps may vary depending on the vehicle and may require specialized equipment and knowledge for accurate performance. The following are basic steps, but refer to a vehicle-specific repair guide for detailed instructions.
Basic Step #1
Most NOx sensors used in diesel automotive and truck applications are usually easily accessible. However, they can be difficult to remove due to temperature fluctuations within the exhaust system. Therefore, make sure it is necessary to remove the sensor before doing so. Most sensor testing can be done from the connector. Refer to the service manual for NOx sensor pinpoint tests to obtain the desired values.
NOTE: When replacing the NOx sensor, it may be necessary to use heat to avoid stripping the threads in the exhaust bung. Applying penetrant oil is always a good idea if you anticipate removing the sensor in the near future.
Basic Step #2
Inspect the harness connected to the NOx sensor to assess its condition. Often, the harnesses are located close to the extreme heat mentioned earlier. Look for any melted wire looms or connectors and repair any chafes or damage to prevent future malfunctions.
Basic Step #3
Visually examine the exhaust system, particularly the interior, to determine if there is a significant amount of soot that could potentially affect the sensor’s functionality. Diesel engines typically produce more soot than gasoline engines. Aftermarket programmer upgrades may also affect the fuel mixture and result in excessive soot, which can lead to premature NOx sensor failure. Clean the sensor if necessary and return the fuel mixture to normal OEM specifications by removing or disabling the programmer.
Basic Step #4
If all other resources have been exhausted and the issue cannot be pinpointed, it is advisable to check the Engine Control Module (ECM) for any water intrusion. The ECM is often located in the vehicle’s interior and may be susceptible to moisture from various sources (e.g., leaking heater core, window seals, melting snow, etc.). If significant damage is found, the ECM will need to be replaced. In most cases, the new ECM will need to be reprogrammed to ensure seamless adaptation. Generally, only dealerships have the necessary tools for programming.
This article is for informational purposes only, and it is always important to prioritize the technical data and service bulletins specific to your vehicle.
