What does it mean?
This diagnostic code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by brand/model.
A vehicle’s catalytic converter helps improve exhaust emissions by oxygenating exhaust gases. It helps convert hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) into water vapor (H₂O), carbon dioxide (CO₂), and nitrogen (N).
The PCM (Powertrain Control Module) monitors catalyst efficiency through a post-catalyst oxygen sensor. This sensor is primarily used for this purpose. It should switch much slower than the upstream oxygen sensors. If at any time the PCM detects that the post-catalyst oxygen sensor is switching too quickly (indicating no change between the catalytic converter’s input and output), it interprets this as a malfunctioning catalyst.
Bank 2 is the engine side that does *not* contain cylinder #1.
Symptoms
Symptoms of a DTC P0432 may include:
Increased exhaust emissions
MIL (Malfunction Indicator Lamp) illumination
Causes
Potential causes
of a P0432 code include:
Faulty or non-functioning catalytic converter
Engine running with non-optimal air/fuel ratio
Possible Solutions
Catalytic converters contain precious metals like platinum, palladium, rhodium among others. Basically, the cheaper the cat, the fewer precious metals used. It’s worth noting that some car brands are very particular about catalytic converters and the logic the PCM uses to monitor them. Just because the parts guy says it will work doesn’t mean it will. The reason is that the vehicle engineering was done with a high-quality catalyst in mind, and it cannot be replaced with a low-cost catalyst. There are also different types of catalysts. Some brands will allow a cheaper catalyst while others simply won’t. Toyotas & Subarus are most known for this. Subarus require CARB-certified catalysts to turn off the check engine light and will not tolerate an aftermarket catalyst, regardless of price.
So basically, if you have a recurrence of this code after replacing the catalyst with an aftermarket one, that might be your problem. If you have this code and haven’t replaced the cat, there are essentially two likely causes: the catalyst is no good or the engine lacks optimal air/fuel ratio. A tune-up or engine repair might fix it. Otherwise, you’ll need to replace the catalytic converter.