P2200 NOx Sensor Circuit Bank1
P2200 code definition
A P2200 code means that the PCM has detected readings in a NOx (nitric oxide/nitrogen dioxide) sensor circuit that’s out of parameters for a specific engine bank.
What the P2200 code means
The PCM analyzes data on exhaust gas composition and temperature from the engine’s oxygen sensors, and calculates typical limits for NOx sensor circuit inputs. If these levels aren’t detected, the PCM will store a hard trouble code and illuminate the malfunction indicator lamp (MIL).
What causes the P2200 code?
More often than not, the P2200 code is caused by a failed catalytic converter. In some cases, a failed O2 sensor can be a possibility, but usually an O2 sensor-related code will accompany a catalytic converter code. Catalytic converters are designed to last the entire life cycle of the vehicle – meaning that a catalytic converter failure is due to another problem, such as:
- A rich-running condition (possibly due to a faulty coolant temp sensor)
- Failed mass air flow sensor
- Failed manifold air pressure sensor
- Failed fuel pressure regulator or other fuel injection component
- Ignition misfire
- Oil fouling
- Retarded spark timing
Bear in mind that a leaky exhaust manifold, down pipe, flex hose or several other exhaust components mounted upstream from the catalytic converter can also mimic the symptoms of catalytic converter failure and register a code in the PCM.
What are the symptoms of the P2200 code?
Symptoms of a P2200 code can include:
- Illuminated MIL indicator
- Lack of power
- Hissing noise while accelerating
- Engine stalling
- No-start condition
How does a mechanic diagnose the P2200 code?
While a catalytic converter is mounted in the exhaust stream and may resemble a muffler or resonator, its design and function differ greatly from a muffler. Catalytic converters get much hotter than a muffler while the engine is running, and remain hot after the engine is driven. A catalytic converter unit uses a network of interwoven fibers, including a high amount of platinum, packed into the metal housing. These fibers help filter out noxious oxide fragments left over in the exhaust gases, incinerating them at 500 to 800 degrees Fahrenheit. Conditions such as retarded ignition timing, lean-burning fuel mixtures and engine misfires can raise catalytic converter temperatures to a dangerous level, even causing the unit to become red-hot, making it a real danger if a flammable liquid comes in contact with it.
Ensure the catalytic converter isn’t under warranty – the units typically are covered by a 100,000 mile federally-mandated warranty, regardless of vehicle age. If the converter is no longer under warranty, start looking for exhaust leaks. Repair as necessary, reset any trouble codes and retest the system. A scanner, digital volt/ohmmeter and infrared temperature gun with laser pointer will be helpful.
Perform a visual inspector of any wiring and connectors. Find a factory wiring schematic to ensure you’ve covered all the wiring harness. Repair/replace any damaged, corroded, disconnected or shorted wiring, components or connectors.
Retest the system after repairs. If all wiring, components and connectors (including fuses) seem to be in working order, connect a scanner or code reader to the diagnostic port. Record stored codes and freeze frame data.
Clear any codes and test drive vehicle to see if codes return. If not, you may have an intermittent problem, which may need to be allowed to worsen in order to make a good, accurate diagnosis.
Start the engine and let it warm up to normal operating temperature. Put the vehicle on a lift and secure it. Point the temperature gun at the exhaust pipe, upstream and downstream from the catalytic converter, and compare temperature readings to manufacturer’s specs. If temp readings do not agree with manufacturer’s specs, that’s a good indication of a catalytic converter problem.
If temp readings are in line with manufacturer’s specs, use the scanner and an oscilloscope to monitor O2 and NOx sensor operation, upstream and downstream on the affected engine bank.
NOx sensors feature a “heater” portion of their electrical circuits, dedicated to warming up the sensors to operating temperature. NOx sensors in most OBD-II-equipped vehicles feature heaters, while oxygen sensors include their own integrated heater circuit.
When the OBD-II heats up the NOx sensor with electrical voltage, it allows it to come up to operating temperature sooner than if it were heated only using exhaust gases. The aim of this is to decrease emissions and decrease time needed for the PCM to operate in closed-loop mode. Heated NOx sensors usually use battery voltage of 12.6 to 13.8 volts. Some models may feature a fuse in this circuit. Other manufacturers have a computer-governed feed of battery voltage and continuous ground, with no fuse needed.
Voltage to individual sensor heater circuits (power and ground) can be tested using a voltage drop method, and test voltages should be close to the voltage of a fully charged battery. If the PCM registers a fault in the circuit voltage or resistance for the heater system, a code will be set and the MIL may be illuminated. If no obvious problem is apparent, connect a scanner and check for any data. Set the scanner’s data stream to read information from only this sensor – you can enhance accuracy and response time from the data stream. A digital volt/ohmmeter can also be used to obtain real-time data, and may help provide more accurate readings.
Readings from NOx sensors mounted upstream of the catalytic convertor will fluctuate between 100-900 milivolts, once the engine is at normal operating temperature and the PCM is in closed loop mode. Downstream NOx sensors should split the difference between lean and rich conditions, and read at 100-200 millivolts near that point at idle. Real-time data or scanner data should read close to these figures – unplug the NOx sensor being tested and examine the pins for damage or corrosion. If a connector is faulty, repair or replace it and clear codes.
Test drive the vehicle. If the connections and pins were in good shape, disconnect the electrical connector on the NOx sensor and perform resistance/continuity testing. If your real-time data still shows readings that are outside of norms for the NOx sensor, disconnect and test the sensor itself. If the battery voltage supply for the sensor heater reads “no resistance,” that may be a good sign the sensor itself is defective. Test the sensor according to manufacturer’s procedures, and compare readings to factory specs. Replace the sensor and clear any codes.
Test drive the vehicle. If the NOx sensor is within factory spec, test other system circuits for resistance and continuity after disconnecting all other related control modules, particularly the PCM. Test all system circuits and compare continuity and resistance readings to manufacturer’s specs. Replace or repair circuits, connectors or components as needed. Test drive the vehicle after repairs are made. If all other readings are close to factory specs, suspect a failed PCM but remember that PCM failures are rare.
Common mistakes when diagnosing the P2200 code
Catalytic converters are designed to last the life cycle of the vehicle. Too often, technicians fail to investigate what caused catalytic converter failure in the first place. Engine misfires, excessively rich exhaust stream and O2 sensor failure can all degrade the platinum element of the catalytic converter. Also, remember that remanufactured or aftermarket catalytic converters are a bad bet and often don’t offer the performance or lifespan of an OEM-quality converter. Don’t forget to rule out codes related to oxygen sensors, fuel trim, fuel mixture or misfires before diagnosing/repairing an NOx sensor-related code.
How serious is the P2200 code?
A P2200 code can result in failed emissions testing, poor performance and the need to replace the catalytic converter.
What repairs can fix the P2200 code?
A P2200 code may require:
- replacement of NOx sensor
- replacement of exhaust leak
- replacement of coolant temperature sensor
- replacement of mass air flow sensor
- replacement of oxygen sensor or other problems resulting in a rich-running condition or misfire.
Additional comments for consideration regarding the P2200 code
Like many other diagnostic codes, a P2200 code can be very tricky to diagnose and repair, and may be accompanied by other codes. It’s necessary to perform a proper process of elimination to avoid replacing parts unnecessarily while still not addressing the root problem.
Need help with a P2200 code?
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