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P0434 OBD-II Trouble Code: Heated Catalyst Temperature Below Threshold (Bank 2)

check engine light

P0434 code definition

The P0434 code indicates that the car’s computer has detected a temperature variance in the catalytic converter.

What the P0434 code means

The P0434 code means the catalytic converter is not working properly. In order for the code to set, the computer must detect the temperature in the catalytic converter bank 2 being lower than acceptable. What this means is that the cat is not burning harmful emissions as it is designed to do. While this will not always result in drivability problems, it will mean that your car cannot pass an emissions inspection, and that you will likely suffer from lower fuel economy. You may also experience other problems depending on the severity of the condition.

What causes the P0434 code?

There are a few possible causes for the P0434 code to set. However, the most common is a failed catalytic converter. Saying that, there are others, including the following:

  • Failed oxygen sensor
  • An air leak in the exhaust before the catalytic converter

As a note, catalytic converters are designed to last the lifetime of the vehicle. While premature failure is not uncommon, there can be underlying causes for this, as well. These include:

  • Using the wrong grade of gasoline consistently
  • A faulty coolant temperature sensor, manifold air pressure sensor or fuel pressure regulator causing excessive fuel to enter the exhaust
  • Leaking exhaust manifold

What are the symptoms of the P0434 code?

The most common symptom with the P0434 code is the Check Engine light illuminating. However, there also may be more than one code stored. Often, an oxygen sensor failure code will accompany the P0434 code. Other possible symptoms also include:

  • Reduced fuel economy
  • Engine hesitation
  • Reduced engine performance
  • Hissing sound on acceleration

How does a mechanic diagnose the P0434 code?

The first step in diagnosing the P0434 code is to connect the car to an OBD II scanner. The mechanic will read the code (or codes) stored, and then clear them. A test drive will be necessary to determine if the codes return. If the codes do return, the next step is to determine if the catalytic converter is under warranty from the manufacturer. Most cars today have a 100,000-mile warranty on the catalytic converter.

If there is an oxygen sensor code, the sensor will need to be replaced before further diagnostics are required. In some instances, replacing a failed O2 sensor will be all that is needed, but this is not always the case.

An exhaust leak test may need to be performed to determine if there is a leak ahead of the catalytic converter. Any leaks must be repaired before further work on the catalytic converter can take place. The codes will need to be cleared again, and the vehicle test driven once any leaks are repaired.

If there are no leaks found in the exhaust, the technician will need to visually inspect all wiring to the catalytic converter, as well as all wiring connections. A voltmeter is also necessary to ensure proper power supply is present. A heat gun may need to be used to verify that converter’s temperature during operation.

Common mistakes when diagnosing the P0434 code

The most common mistake when diagnosing the P0434 code is assuming that it means the catalytic converter is bad. There are many other potential problems, and they must all be eliminated before replacing the catalytic converter.

How serious is the P0434 code?

While the P0434 code might not create drivability problems, the best-case scenario is that you will be using excess fuel and unable to pass your emissions test. Having it properly diagnosed and the condition repaired is very important.

What repairs can fix the P0434 code?

A number of repairs may fix the P0434 code, depending on the underlying condition. These include:

Additional comments for consideration regarding the P0434 code

It is important that technicians conduct a full diagnostic with the P0434 code. While a failed converter is likely, this is not the only potential cause.

Need help with a P0434 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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