P2218 NOx Sensor Heater Control Circuit/Open Bank 2
OBD-II Trouble Code Technical Description
NOx Sensor Heater Control Circuit/Open Bank 2
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) and typically applies to OBD-II vehicles. Vehicle makes may include but aren’t limited to BMW, Dodge, Ram, Audi, Cummins, etc.
NOx (Nitrogen Oxide) sensors are primarily used for the emission systems in diesel engines. Their primary use is to detect NOx levels coming out of the exhaust after burning in the combustion chamber. The system then recycles these using different methods. Given the harsh environment of these sensors, they are composed of a combination of ceramic and a certain type of zirconia.
One of the downfalls of emitting NOx into the atmosphere is that it may cause smog and/or acid rain at times. Failure to sufficiently monitor and adjust NOx levels would result in a significant effect to the atmosphere around us and the air we breathe. The ECM (Engine control module) continuously monitors the NOx sensors to ensure acceptable emissions levels in your vehicle’s exhaust. The NOx sensor heater control circuit is responsible for heating the sensor preemptively. It does this to expedite the sensor warm-up time, in turn bringing to operating temperature efficiently without solely relying on exhaust temperatures to warm itself up.
When it comes to P2218 and related codes, the NOx sensor heater control circuit malfunctioned somehow and the ECM has detected this. For reference sake, Bank 1 is on the side in which the number 1 cylinder is located. Bank 2 is on the other side. If your vehicle is a straight 6 or 4 cylinder, where there is only one head, it may be a two sided downpipe/ manifold. Always refer to your service manual for location designations as this will be integral in the diagnosing process.
P2218 is a generic trouble code that refers to “NOx Sensor Heater Control Circuit/Open Bank 2.” It appears when the ECM detects an open or general malfunction within the NOx sensor heater control circuit on bank 2 .
Diesel engines especially produce a significant amount of heat so make sure to always let the system cool before working on any exhaust system components.
An example of NOx sensor (in this case, for GM vehicles):
What is the severity of this DTC?
Medium severity for this, as emission related faults really can effect the environment around this. That said, sometimes with emission faults, there will not be any symptoms present but can still have repercussions if left unattended.
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?
Causes for this P2218 cruise control code may include:
What are some P2218 diagnostic and troubleshooting steps?
The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins (TSB) for known issues with the specific vehicle.
Advanced diagnostic steps become very vehicle specific and may require the appropriate advanced equipment and knowledge to perform accurately. We include basic steps below but refer to a vehicle year/make/model/powertrain specific repair guide for specific steps for your vehicle.
Basic Step #1
Most NOx sensors used in diesel automotive and truck applications will be fairly accessible. Given that fact, keep in mind they can be extremely stubborn when removing with all the expanding and contracting that is going on with the temperature fluctuations within the exhaust system. So make sure you need to remove the sensor before doing so. Most sensor testing should be able to be done from the connector. Refer to your service manual for NOx sensor pinpoint tests to acquire the desired values.
NOTE: You may need to use some heat when replacing the NOx sensor to avoid stripping the threads in the exhaust bung. Penetrant oil is always a good idea anytime you think you may be removing the sensor in the near future.
Basic Step #2
Follow the harness involved with the NOx sensor to assess its health. Most times the harnesses will be run in close proximity to the extreme heats mentioned earlier. So keep a close eye for any melted wire looms or connectors. Make sure to repair any chafes or damaged wire looms to prevent any future malfunctions.
Basic Step #3
Visually inspect the exhaust system. Especially inside to determine if there is enough soot present that it could potentially adversely effect the sensor’s overall functionality. Generally speaking, diesel engines produced an abnormal amount of soot anyway. That being said, aftermarket programmer upgrades may affect the fuel mixture and create more than normal soot amounts, which can consequently cause premature NOx sensor failure, given the richer fuel mixtures involved with some aftermarket programmers. Make sure to clean the sensor if you think this is the case and return fuel mixture to normal OEM specs by removing or disabling the programmer.
Basic Step #4
Finally, if you’ve exhausted your resources, and still can’t pinpoint the issue, it would be a good idea to locate your ECM (engine control module) to verify if there is any water intrusion present. At times located in the interior of the vehicle, it can be susceptible to any moisture being created in the interior overtime (e.g. leaking heater core, leaking window seals, melting residual snow, etc.). If any substantial damage is found, it will need to be replaced. To do this, in most cases, the new ECM will need to be reprogrammed to the vehicle so adaptation is seamless. Unfortunately, generally speaking, the dealerships will be the only one equipped with the proper tools for programming.
This article is strictly for information purposes only and the technical data and service bulletins for your specific vehicle should always take precedence.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p2218 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p2218 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p2218.
