Fault code P0422 – main catalyst efficiency below threshold (Bank 1)

Fault code P0422 is called “Main Catalyst Efficiency Below Threshold (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 P0422

This Diagnostic Trouble Code (DTC) is a general powertrain code. Error P0422 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

Fault code P0422 – main catalyst efficiency below threshold (Bank 1)

The vehicle’s catalytic converter (catalyst) helps reduce exhaust emissions by oxygenating them. It helps convert hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) into water vapor (H₂O), carbon dioxide (CO₂) and nitrogen (N).

The PCM (transmission control module) monitors the efficiency of the catalyst with an oxygen sensor after the catalyst. This sensor is used primarily for this purpose. It should switch much slower than the front oxygen sensors.

If at any time the PCM detects that the O₂ sensor after the catalyst is switching too fast (indicating no change between the input and output of the catalytic converter). It identifies this as the catalyst not working properly and outputs error code P0422 OBD2.

Symptoms of vehicle malfunctions

The main signal that an error P0422 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Check engine control lamp on the control panel will light up (the code will be written to the ECM memory as a fault).
  2. The engine stops or starts badly.
  3. Decrease in engine power output.
  4. Increased emission of harmful substances from the exhaust pipe.

The most common cause of fault P0422 is a faulty catalytic converter, which can cause the engine to frequently stall or struggle to start. However, if the catalytic converter is OK, there should be no serious problems. In any case, if this code is found, it is advisable to correct the problem as soon as possible.

Factors that can cause this error code

The error code P0422 can mean that one or more of the following problems have occurred:

  • Bad or non-functional catalytic converter.
  • Faulty oxygen sensor.
  • Engine is not running at optimum air/fuel ratio.
  • Engine coolant temperature sensor has failed.
  • Engine leaking in front of catalytic converter.
  • Ignition misses in engine cylinders.
  • Damaged wires and connectors.
  • Problems with manifold air pressure sensor.
  • Contamination of engine oil due to not changing regularly.
  • Air flow sensor failed.
  • Faulty fuel pressure regulator.

How to fix or reset OBD-2 code P0422

Some suggested steps for troubleshooting and fix the error code P0422:

  1. Inspect the sensor wires near the catalytic converter.
  2. Check the oxygen sensors.
  3. Repair any leaks in the engine.
  4. Test the air flow sensor as well as the manifold air pressure.
  5. Check the fuel pressure regulator.
  6. Test the engine coolant temperature sensor.
  7. If no problems are found, check the catalytic converter and replace it if necessary.

Diagnose and repair of problems

Error P0422 is diagnosed with a standard OBD-II scanner. Use the scan tool to view the data and gather information about the code. Also to check other error codes that may be present.

Then clear the error codes from the PCM memory and recheck the system to see if error P0422 appears again. If the code disappears, it may indicate an intermittent error or that the code appeared in error.

If error P0422 occurs again, inspect the wires and connectors near the catalytic converter. Repair or replace any damaged items. After that, inspect the catalytic converter and also perform a thorough check of the exhaust system for leaks.

If the problem is with the catalytic converter, replace it. Also inspect other vehicle components to determine the cause of catalytic converter damage.

On which vehicles does this problem occur most frequently

Fault code P0422 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
  • Chevrolet
  • Chrysler
  • Dodge (Caravan)
  • Ford
  • Hyundai (Accent, Elantra)
  • Kia (Spectra, Sportage)
  • Mercedes-Benz
  • Mitsubishi
  • Peugeot (206)
  • Volkswagen (Beetle, Jetta)
  • Volvo
  • GAZelle (Business, Next)
  • LADA (Granta, Kalina, Niva, Priora, Vesta)
  • UAZ
  • VAZ (2104, 2105, 2107, 2110, 2111, 2112, 2113, 2114, 2115)
  • Volga (31105, Chrysler)

Fault code P0422 can sometimes be found with other errors. The most common are the following: P0304, P0326, P0420, P0441, P0455.


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