What Does the Engine Code P2431 Mean?

If your car is showing the P2431 engine code, you’re dealing with a problem with your secondary air injection system.
Written by Melanie Johnson
Reviewed by Melanie Reiff
If your car is showing the P2431 engine code, it means that your secondary air system, which pumps fresh air into the exhaust to reduce vehicle emissions, has a problem. An incorrect airflow has been detected, and you should get it fixed promptly to avoid a failed emissions test.
Diagnostic trouble codes (DTCs) were designed to help you identify problems with your car’s engine. If you own a code reader, you’ll be able to
understand these OBD codes
, locate the problem, and fix the source of your car trouble. 
Being an informed driver is important—that’s why
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is here to provide you with expert information on engine codes. In this article, we’re breaking down the P2431 engine code: what it means, how to repair it, and how much it will cost to fix. 
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What does the engine code P2431 mean?

Definition: Secondary air injection system air flow/pressure sensor circuit range behaving deficiently (Bank 1)
The P2431 engine code indicates a problem with your car’s secondary air injection system, which is vital in reducing emissions of toxic pollutants, such as nitrogen dioxide, carbon monoxide, hydrocarbons, and others. 
Located on the engine or close to the engine bay, the air injection system pumps fresh air into the engine just before the catalytic converter. The more fresh air your car has in its exhaust system, the more effectively the catalytic converter can work to keep these toxic pollutants from being released. 
When your secondary air injection system is damaged or broken, it likely means toxic pollutants are being released from your car.
MORE: How to pass emissions testing

How much will it cost to fix?

If you need to replace part of your secondary air injection system, the total cost of parts and labor will depend on what part of the system needs to be repaired.
The three main repairs to the secondary air injection system and their costs are:
  • Replacing the secondary air pump: $270 to $390
  • Resolving poor electrical connections: $50 to $400 
  • Rewiring or replacing a wiring harness: $1,000 to $1,500

What can cause the P2431 engine code?

The most likely cause of your car showing the P2431 engine code is a faulty secondary air pump. It’s likely that moisture from the exhaust is causing the pump to fail.
Other potential triggers of this engine code include: 
  • Faulty air pressure sensor
  • Air pressure sensor harness is open or shorted
  • Air pressure sensor circuit has a poor electrical connection

Common symptoms of the P2431 engine code

A Check Engine Light is sometimes the only sign that the secondary air injection system is not working correctly. Other potential symptoms to look for include: 
  • Car stalling
    or running poorly
  • Engine hesitating or bucking under acceleration
  • Failed emissions test
Because the signs of a faulty secondary air system are often tough to spot, it’s a good idea to bring it in for an assessment as soon as the
Check Engine Light turns on
.

Can I fix the P2431 engine code myself?

It may be possible to fix the P2431 engine code at home, but it’s important to accurately diagnose the issue correctly, which may be difficult if you’re not experienced. 
Depending on the source of the problem, you may need to replace the air pump, which is a task that can be accomplished at home with the right tools. However, if the problem has to do with replacing or rewiring the electrical system of your car, you’re better off leaving that to an experienced mechanic.

Replacing the secondary air pump

If you do decide to replace the secondary air pump yourself, you’ll need to follow these steps:
  • Locate the air injection pump at the front of the engine.
  • Remove the serpentine belt wrapped around the pump.
  • Remove the hose, vacuum lines, and electrical connections.
  • Remove the air pump mounting bolts and the pump itself.
  • Install the new air pump.
  • Replace and reinstall all removed parts.

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