Technical Description of OBD-II Trouble Code
Bank 1 NOx Sensor Heater Control Circuit/Open
What does that signify?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II vehicles, including BMW, Dodge, Ram, Audi, Cummins, and others.
NOx (Nitrogen Oxide) sensors are primarily used in diesel engines for emission systems. They detect NOx levels in the exhaust after combustion in the combustion chamber. The system then recycles these emissions using various methods. Due to the harsh environment, these sensors are made of ceramic and a specific type of zirconia.
One of the negative impacts of emitting 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 emissions levels in the vehicle’s exhaust. The NOx sensor heater control circuit is responsible for preheating the sensor to expedite the warm-up time and reach operating temperature efficiently, without relying solely on exhaust temperatures.
When encountering P2205 and related codes, it means that the NOx sensor heater control circuit has malfunctioned and the ECM has detected it. 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.
P2205 is a generic trouble code that indicates “NOx Sensor Heater Control Circuit/Open Bank 1.” It appears when the ECM detects an open or general malfunction in the NOx sensor heater control circuit on bank 1.
Diesel engines generate a significant amount of heat, so it is important to let the system cool before working on any exhaust system components.
An example of a NOx sensor (for GM vehicles):
What is the severity of this DTC?
This DTC has a medium severity level because emission-related faults can have an 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 P2205 diagnostic code may include:
What are some of the common causes of the code?
Possible causes for this P2205 code may include:
What are some diagnostic and troubleshooting steps for P2205?
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 are highly vehicle-specific 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. Ensure that sensor removal is necessary before proceeding. Most sensor testing can be done from the connector. Consult 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. The harnesses are often located near the extreme heat mentioned earlier, so check for any melted wire looms or connectors. Repair any chafes or damaged wire looms to prevent future malfunctions.
Basic Step #3
Visually examine the exhaust system, particularly the interior, to determine if there is excessive 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 higher soot levels, leading 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 require reprogramming by a dealership equipped with the necessary tools.
This article is for informational purposes only, and the technical data and service bulletins specific to your vehicle should always take precedence.
