P0432 Main Catalyst Efficiency Below Threshold (Bank 2)

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P0432 Main Catalyst Efficiency Below Threshold (Bank 2)

OBD-II Trouble Code Technical Description

Main Catalyst Efficiency Below Threshold (Bank 2)

What does that mean?

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Although generic, the specific repair steps may vary depending on make/model.

A vehicles’ catalytic converter (catalyst) helps improve tailpipe emissions by oxygenating the exhaust gasses. It helps convert hydrocarbons (HC), Carbon Monoxide (CO), and oxides of Nitrogen (NOx) into water vapor (H20), Carbon Dioxide (CO2), and Nitrogen (N).

The PCM (Powertrain control module) monitors the catalyst efficiency by means of a postalyst Oxygen sensor. This sensor is used primarily for this purpose. It should switch much slower than the front oxygen sensors. If at any point the PCM detects that the postalyst o2 sensor is switching too rapidly (indicating no change between the inlet and outlet of the catalytic converter) it interprets this as a catalyst that isn’t functioning properly.

Bank 2 is the side of the engine that does *not* contain cylinder #1.

Symptoms

Symptoms of a P0432 DTC may include:

  • Increased tailpipe emissions
  • MIL (Malfunction Indicator Lamp) illumination
  • Causes

    Potential causes of a P0432 code include:

  • Bad or non-functional catalyst
  • Engine operating out of optimal air:fuel ratio
  • Possible Solutions

    Catalytic converters contain precious metals like platinum, palladium, rhodium among others. Basically, the cheaper the cat, the less precious metals used. It should be noted that there are some automobile makes that are very finicky when it comes to catalytic converters and the logic that the PCM uses to monitor them. Just because the parts guy says it will work doesn’t mean that it will. The reason is that the engineering of the vehicle was done with a high quality catalyst in mind and it can’t be replaced with a low cost catalyst. There are also different kinds of catalysts. Some makes will allow for a cheaper catalyst while others simply will not. Toyotas & Subarus are the most notorious for this. Subarus require CARB certified catalysts to keep the check engine light off and won’t tolerate an aftermarket catalyst, no matter how expensive.

    So basically if you have a recurrence of this code after replacing the catalyst with an aftermarket catalyst, this may be your problem. If you have this code and haven’t replaced the cat, there’s basically two likely causes: The catalyst is no good, or the engine is running out of optimal air:fuel ratio. A tune up or engine repair may correct it. Otherwise you’ll need to replace the catalyst.

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    "Delete Error Code Permanently, Disable DTC Error Code Function for p0432 in the ECU"

    In extreme cases, we even have the option to permanently remove the specific DTC p0432 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.

    Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0432.

    Make an appointment for permanent removal of p0432