Fault code P2203 is called “Nitrogen Oxides (NOx) Sensor Circuit High (Bank 1)” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P2203
Diagnostic code P2203 is a generic code that is defined as a high signal level in the nitrogen oxide sensor circuit (Bank 1). It is set when the Powertrain Control Module (PCM) detects a failure or malfunction with the NOx sensor itself or the control circuit.
The control module monitors countless sensors to keep your engine efficient, reliable and running. It also actively monitors emissions and ensures that as few hydrocarbons as possible are released into the atmosphere.
The PCM uses NOx sensors to monitor nitrogen oxide levels in the exhaust to get an idea of the amount of hydrocarbons being emitted. Since NOx is one of the main pollutants that diesel engines produce.
The ECM will activate error P2203 and related codes when it monitors a high level of NOx sensor signal or its circuits. In most cases, this will be a mechanical failure, especially given the conditions of the sensor.
When the PCM detects a high signal level in the NOx sensor or its control circuits, it sets code P2203, after which the warning light will illuminate. If the signal lamp is flashing, it indicates a serious problem that may be affecting the catalytic converter.
Symptoms of vehicle malfunctions
The main signal that an error P2203 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the memory as a fault).
- Increase of harmful emissions.
- Floating revolutions, as well as attempts to stall at idle.
- Skipping engine ignition under load or at idle.
- Reduced engine power output.
- Increased fuel consumption.
- Excessive smoke from the exhaust pipe.
The P2203 error is not considered very serious, however, like any problem, it is recommended to solve it. With this code, you will most likely not pass the emissions test, as the emissions will be exceeded.
Factors that can cause this error code
The error code P2203 can mean that one or more of the following problems have occurred:
- Defective or damaged NOx sensor.
- NOx sensor is dirty.
- Damaged or worn NOx sensor connector.
- Damaged wiring.
- Sometimes faulty PCM module is the cause.
How to fix or reset OBD-2 code P2203
Some suggested steps for troubleshooting and fix the error code P2203:
- Connect the OBD-II scanner to the vehicle’s diagnostic connector and read all stored data and error codes.
- Clear the error codes from the computer memory and test-drive the vehicle to see if the code P2203 appears again.
- If the code appears again, check the cables and corresponding connectors leading to the NOx sensor. Make sure they are not broken or frayed. Repair or replace if necessary.
- Inspect and test the NOx sensor, and replace if necessary if it has failed.
- If faulty PCM is the cause, replace or reprogram it.
Diagnose and repair of problems
Inspect visible damage to the sensor, wiring, and connectors. Then start the diagnostic procedure with the scan tool. To determine if error P2203 is the only error, if not, it may be worth investigating the other fault codes first.
If no problems are found with damaged or corroded connectors, perform a thorough inspection of all associated wiring. Repair or replace damaged wiring as necessary.
Check wiring and NOx sensor
If no visible wiring damage is found, prepare to perform reference voltage, ground, resistance, and continuity tests. Be sure to disconnect the sensor from the wiring harness so as not to damage the PCM and avoid a short circuit.
The NOx sensor is part of the control circuit, it must also be tested. Compare all readings on the sensor with those in the manual. Replace the sensor if the reading is out of the specified range or value.
When replacing the NOx sensor, make sure that all connections are secure and that all wiring is secured away from hot components. Then start the engine and allow it to warm up to normal temperature to allow the new sensor to go into closed loop mode.
The main cause of error P2203 is in a faulty NOx sensor, so replacing it should solve the problem.
On which vehicles does this problem occur most frequently
Fault code P2203 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Audi
- BMW
- Chevrolet
- Dodge (RAM)
- Ford
- GMC
- Jeep
- Mercedes-Benz (ML350, Sprinter, W163, W203, W211)
- Ssangyong (Kyron, Rexton)
- Volkswagen
Fault code P2203 can sometimes be found with other errors. The most common are the following: P2200, P2201, P2202, P2204.
