Technical Description of OBD-II Trouble Code
Open Circuit or Control Issue in Bank 2 NOx Sensor Heater
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 to detect NOx levels in the exhaust after combustion. These sensors are made of ceramic and zirconia due to the harsh environment they operate in. Emitting NOx into the atmosphere can cause smog and acid rain, so it’s important to monitor and adjust NOx levels. The NOx sensor heater control circuit is responsible for preheating the sensor to operating temperature efficiently. The P2218 code indicates a malfunction in the NOx sensor heater control circuit on bank 2.
Bank 1 refers to the side where the number 1 cylinder is located, while bank 2 refers to the other side. For vehicles with a straight 6 or 4-cylinder engine, bank 2 may be a two-sided downpipe/manifold. Consult the service manual for location designations during the diagnostic process.
P2218 is a generic trouble code that indicates an open or general malfunction in the NOx sensor heater control circuit on bank 2.
Diesel engines generate a significant amount of heat, so it’s important to let the system cool before working on any exhaust system components.
Example of a NOx sensor for GM vehicles:
What is the severity of this DTC?
This DTC has a medium severity level due to its impact on the environment. Although there may not be any noticeable symptoms, leaving emission-related faults unattended can have repercussions.
What are some of the symptoms of the code?
Symptoms of a P2218 diagnostic code may include:
What are some of the common causes of the code?
Possible causes of the P2218 code include:
What are some P2218 diagnostic and troubleshooting steps?
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 require specific equipment and knowledge. The following basic steps can be taken, but refer to a vehicle-specific repair guide for detailed instructions:
Basic Step #1
Most NOx sensors in diesel vehicles are easily accessible. Testing can often be done from the connector without removing the sensor. Consult the service manual for NOx sensor pinpoint tests and desired values.
NOTE: When replacing the NOx sensor, use heat to avoid stripping the threads in the exhaust bung. Penetrant oil is recommended if the sensor may be removed in the future.
Basic Step #2
Inspect the harness connected to the NOx sensor for any damage. The harnesses are often exposed to extreme heat, so look for melted wire looms or connectors. Repair any chafes or damaged wire looms to prevent future malfunctions.
Basic Step #3
Visually inspect the exhaust system, especially the interior, for excessive soot that could affect the sensor’s functionality. Diesel engines produce more soot than gasoline engines, and aftermarket programmer upgrades can increase soot levels. Clean the sensor if necessary and return the fuel mixture to normal OEM specifications by removing or disabling the programmer.
Basic Step #4
If the issue cannot be pinpointed, check for water intrusion in the ECM. Moisture from sources like a leaking heater core or window seals can damage the ECM. If substantial damage is found, the ECM will need to be replaced and reprogrammed by a dealership.
This article is for informational purposes only, and vehicle-specific technical data and service bulletins should always be consulted.
