The P0422 code alerts you to an issue with the efficiency of the catalytic converter’s main catalyst in the first bank or the side of the engine that contains the first cylinder. The
Powertrain Control Module (PCM) determines the efficacy of the catalyst system by analyzing the exhaust and temperature conditions from both the upstream oxygen sensor and the downstream oxygen sensor.
The front sensor’s readings usually fluctuate to reflect the car’s normal operating closed-loop condition. When the PCM determines that the readings from both sensors are too similar, it assumes that the catalyst’s efficiency is most likely below a predefined threshold.
Once this is determined, the PCM triggers the P0422 code to indicate the catalyst inefficiency.
What Does Code p0422 Mean?
Diagnostic trouble code (DTC) P0422 stands for “Catalyst 2 Efficiency Below Threshold (Bank 1).” It indicates that the emissions efficiency of Bank 1 catalytic converters are below the minimum allowable limit.
This threshold is monitored by the catalyst monitor oxygen sensor, which is located near the catalytic converter’s outlet.
The purpose of your car’s catalytic converter is to oxygenate the exhaust gasses and improve tailpipe emissions. It is monitored by the catalyst monitor oxygen sensor.
The engine control module (ECM) tracks the switching frequency of the heated oxygen sensors 1 and 2 (front and rear sensors).
A functional three way catalyst converter typically indicates a low switching frequency of heated oxygen sensor 2. The frequency increases as the converter deteriorates.
The P0422 code is logged when the frequency ratio of both heated oxygen sensors 1 and 2 reaches the threshold.
You can get more helpful information in our technical discussion about how cat converters work and catalytic converter efficiency.
Potential Causes of a p0422 Code
The major reasons that can lead to the error code P0422 are mentioned below.
- A faulty oxygen sensor
- Damage in the coolant temperature sensor
- Fault in the manifold air pressure sensor
- Defect with the mass air flow sensor
- Polluted engine oil
- Front engine leak from the catalytic convertor
- Faulty engine
- Loose wires and connections
What are the Common Symptoms of the P0422 Code?
The most commonly reported symptom for the P0422 error code is an illuminated Check Engine Light (CEL). Other symptoms are:
- Stalls when revved
- Failed emissions testing
- Cylinder misfires
- Poor acceleration
- “Rotten egg” or sulfur odor
How to Fix p0422 code?
Correcting the P0422 error code deals mainly with the catalytic converters and sensors. Here are ways to fix if this error arises.
- Catalytic converter replacement
- Replacing oxygen sensors
- Replacing the wires of the electrical connectors
- Fixing the engine leaks
- Mass airflow sensor replacement
- Fixing the fuel pressure regulator
- Manifold air pressure sensor correction
- Replacing the coolant temperature sensor
How does a mechanic diagnose the P0422 code?
The P0422 trouble code will be diagnosed using a standard OBD-II trouble code scanner. A trained mechanic will use the trouble code scanner to assess the P0422 code and search for additional trouble codes.
Following this, the technician will reset the trouble codes and restart the vehicle. If the code does not return, it was likely falsely triggered, and there is no issue.
If the P0422 code (and any accompanying trouble codes) returns, the mechanic will inspect all of the wiring and connectors near the catalytic converter.
If any are loose or damaged, they should be replaced, and the codes should be reset to see if the issue is resolved. After the wires and connectors, a technician should inspect the catalytic converter itself, and should also search for leaks in the exhaust system.
If an issue is noted with the catalytic converter, the mechanic will inspect other areas of the vehicle to try and find the cause of the catalytic converter damage, as they are usually the result of an issue elsewhere in the engine.
Common mistakes when diagnosing the P0422 code
The most common mistake made when diagnosing the P0422 code comes from not properly following the OBD-II trouble code diagnosis protocol.
Failure to follow the protocol may result in replacing the catalytic converter without addressing the issue that is causing the converter to fail, or failure to address other present trouble codes.
It is also common for oxygen sensors to be replaced erroneously. While an oxygen sensor could be part of the issue triggering the P0422 code, it is unlikely to be the primary problem.
Oxygen sensors should be inspected before being replaced, and should not be assumed to be the sole problem causing the P0422 code.
How serious is the P0422 code?
The severity of the P0422 code can greatly vary. If the issue is a faulty catalytic converter, the vehicle may not start, or may frequently stall. In this case, the car will be close to not drivable.
However, if the catalytic converter is not the problem, the car should experience little to no issues driving. However, the code should still be addressed as failure to do so may ultimately result in serious damage to the catalytic converter.
How Much Does It Cost to Fix a p0422 Code?
Fixing a P0422 code, which indicates a problem with the catalytic converter efficiency, typically costs between $300 and $1,000 depending on your car model.
The severity of the issue, and whether you need to replace the catalytic converter itself; the cost of the part can vary significantly, with labor costs adding to the total price.