P0432 Main Catalyst Efficiency Below Threshold (Bank 2)

Technical Description of OBD-II Trouble Code

The main catalyst efficiency is below the required threshold on Bank 2.

What does that signify?

This diagnostic trouble code (DTC) is a standard powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.

A vehicle’s catalytic converter (catalyst) helps improve the emissions from the tailpipe by oxygenating the exhaust gases. It converts hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) into water vapor (H20), carbon dioxide (CO2), and nitrogen (N).

The powertrain control module (PCM) monitors the efficiency of the catalyst using a post-catalyst oxygen sensor. This sensor is primarily used for this purpose and should switch at a slower rate compared to the front oxygen sensors. If the PCM detects that the post-catalyst oxygen sensor is switching too rapidly (indicating no change between the inlet and outlet of the catalytic converter), it interprets this as a malfunctioning catalyst.

Bank 2 refers to the side of the engine that does not contain cylinder #1.

Symptoms

The symptoms of a P0432 DTC may include:

Causes

Possible causes of a P0432 code include:

Possible Solutions

Catalytic converters contain precious metals such as platinum, palladium, and rhodium, among others. Generally, cheaper catalytic converters use fewer precious metals. It should be noted that certain automobile makes are very particular about catalytic converters and the PCM’s monitoring logic. Just because the parts supplier claims it will work does not guarantee its compatibility. The vehicle’s engineering was designed with a high-quality catalyst in mind, and it cannot be replaced with a low-cost catalyst. Additionally, there are different types of catalysts available. Some makes may allow for a cheaper catalyst, while others strictly require a specific type. Toyotas and Subarus are particularly known for this. Subarus require CARB certified catalysts to prevent the check engine light from illuminating and will not tolerate an aftermarket catalyst, regardless of its cost.

Therefore, if you experience a recurrence of this code after replacing the catalyst with an aftermarket one, it may be the cause of the issue. If you have this code and have not replaced the catalytic converter, there are two likely causes: the catalyst is faulty or the engine is operating outside the optimal air:fuel ratio. A tune-up or engine repair may resolve the issue. Otherwise, you will need to replace the catalytic converter.

Professional Service

While we always recommend resolving this issue through mechanical means, if it is not feasible for any reason, we offer the option to permanently delete this specific DTC. We will continue to address all other codes. If you are interested in this option, please upload your ECU file to our portal.