1. Home
  2. /
  3. Complete List of OBD2...
  4. /
  5. P0422 Code – What...

P0422 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


If your OBD2 is displaying trouble code P0422, that code means that your main catalyst efficiency is below threshold.


What does that mean for the driver or vehicle owner?

Trouble code P0422 is a generic OBD2 trouble code that indicates that the vehicle’s catalyst efficiency is noticeably below the normal threshold that it should be. 

This threshold is within the first engine bank, the part of the engine that generally houses the vehicle’s number one cylinder.

How is the efficiency of the catalyst gauged?

The efficiency of a vehicle’s catalyst is determined by the PCM (powertrain control module). The PCM collects temperature and exhaust data from the downstream and upstream oxygen sensors in the vehicle. This gives the PCM the information that it needs to determine and regulate the efficiency of the catalyst.

If the PCM finds that the readings from both the downstream and upstream sensors are too similar, that is adequate enough information to determine that the function of the catalyst is likely below the operating threshold. When the PCM registers these readings, a P0422 trouble code will display on your OBD2.


Now that we have a better understanding of what a P0422 trouble code is, what are some of the most common reasons that this trouble code would occur?

The most common cause for this trouble code that indicates your main catalyst efficiency is below threshold is that the vehicle has a malfunction in its catalytic converter. Even though that is one of the most common reasons that this trouble code appears, there are several other issues that can trigger this trouble code to display on your OBD2.

Some of the other most common reasons that code P0422 occurs is due to the fact that:

  • Either the downstream and/or upstream oxygen sensor is faulty
  • The coolant temperature sensor is malfunctioning
  • The fuel pressure regulator is experiencing difficulties
  • The air pressure sensor has a faulty manifold
  • The mass air flow sensor is malfunctioning
  • The engine oil is contaminated
  • The engine could be leaking upstream from the catalytics converter
  • The engine could be misfiring
  • That connectors or wires are damaged or loose


When you are experiencing a P0422 trouble code, then check engine warning lights should be illuminated prominently on the dashboard. This is the first signal to the driver that there is a problem with the vehicle.

There are a few signs that the driver may clue in on that there is a greater problem with the vehicle, outside of the warning light or the trouble code. The driver may notice that the engine’s performance is diminishing. With some vehicles, you will hear a hissing noise from the motor or hesitation from it, when the throttle is engaged. This can cause the engine to stall or stop it from starting completely.

Also Read: Why Does My Car Make Noise When Turning


How do you go about diagnosing a P0422 trouble code?

A skilled mechanic will be able to use the OBD2 scanner to first identify that a P0422 trouble code is present. Next, they will systematically search for additional trouble codes that could be related to the problem. Afterward, they will reset the trouble codes, and restart the vehicle. If they see that the code or the codes that they saw before are not displayed on the OBD2 scanner, there is likely no issue and those codes may have been falsely triggered.

If the code and other related trouble codes return after clearing the codes and restarting the vehicle, the mechanic will inspect the connectors and wires near the catalytic converter to make sure there isn’t a loose or faulty connection. They will replace any damaged connectors and wires. Next, they will check the catalytic converter for leaks in the exhaust system.

From there, the mechanic will continue to inspect and analyze other areas of the vehicle to further investigate why the catalytic converter was damaged.

Common mistakes

The most common mistake with a P0422 trouble code is not following code diagnosis protocol. This commonly leads a mechanic to replace a catalytic converter without looking into other related issues or components that could have caused the converter to fail.

One of the other most common mistakes that inexperienced mechanics have with this trouble code is that they will replace oxygen sensors without knowing for certain that they caused this trouble code. A faulty oxygen sensor code by part of the issue, however, it is unlikely in the event of this trouble code. Regardless, a mechanic should never assume that is the sole source of this trouble code.

How serious is this?

A P0422 trouble code can vary in the level of its severity. The code is caused by a faulty catalytic converter, the vehicle may stall frequently or not start at all. In this circumstance, the car may be partially or completely not drivable.

If the catalytic converter is not the source of the problem, you may notice little to no problems with the drivability of the vehicle. In either case, the code should be investigated by a mechanic so they can identify and fix the problem.

What repairs can fix the code?

  • Replacing the catalytic converter
  • Replacing the oxygen sensors
  • Replacing the connectors and/or wiring
  • Replacing the mass airflow sensor
  • Fixing any engine leaks
  • Replacing the manifold air pressure sensor
  • Replacing the fuel pressure regulator
  • Replacing the coolant temperature sensor

Related codes

None listed.


Though a P0422 trouble code may not be immediately detrimental to your vehicle, it is something that should be investigated and fixed as soon as possible. If the problem is properly diagnosed and investigated, it is something that can be fixed fairly easily.

P0422 Code – What Does It Mean & How To Fix It