What Codes Will This Page Cover?
This page will cover the following two codes:
- P0491 Diagnostic Code: Secondary Air Injection System Insufficient Flow Bank 1
- P0492 Diagnostic Code: Secondary Air Injection System Insufficient Flow Bank 2
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What Is the P0491 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
Get Additional Help
The P0491 and P0492 codes indicate that there’s an issue within the secondary air injection (SAI) system. This is part of the emissions system, air from the atmosphere into the exhaust to heat up the catalytic converter after a cold start in order to process certain emissions, such as carbon monoxide and various hydrocarbons. It injects ambient air into the exhaust, which helps with the facilitation of an overall lower emissions rate. If you’re seeing this code, it means the powertrain control module (PCM) has identified that the SAI system is dealing with insufficient flow.
More About the P0491 and P0492 Codes
Not all vehicles have an SAI system, but in those that do, this system can be generally complex and full of a variety of solenoid-operated valves, which will direct airflow appropriately. If the PCM determines that airflow is low for an extended period of time, it will trigger this code. The only difference between the codes is which bank it identifies a problem with—P0491 refers to bank 1, while P0492 refers to bank 2.
What Are the Symptoms of a P0491 Code?
The P0491 and P0492 codes rarely cause significant symptoms. You should expect to see the check engine light turn on, and you may also hear some abnormal noises from the air pump, including hissing sounds. In some cases, you might see sluggish acceleration or stalling while idling, although it’s equally as likely that you might see no symptoms at all outside of just the check engine light.
What Are Some Causes of a P0491 Code?
The P0491 and P0492 codes can happen due to a variety of reasons. Most faults occur when the one-way check valve in the air inlet fails, allowing the hot exhaust gasses to flow past the valve and into the injection pump, which will permanently damage the internal pump. However, it may also occur because faultiness of the system relay, the air injection pump, or a secondary air pressure sensor, problems with clogged secondary air injection ports, or general problems with wiring, connectors, and sensor connections. It may also be due to vacuum leaking issues.
How Serious Is the P0491 Code?
While not exceptionally serious at first, the P0491 and P0492 codes can certainly develop into serious concerns, especially if the problem is due to vacuum leaks. Additionally, these codes can cause your vehicle to fail an emissions test, which can be a problem if you need to pass the emissions test anytime soon. It’s always a good idea to fix problems as soon as they come up, even if they don’t seem especially significant.
Can I Still Drive with a P0491 Code?
It is usually still possible to drive when your vehicle is displaying the P0491 and P0492 codes. However, you should avoid driving when your vehicle has a check engine light code on. These codes can develop into other codes, causing issues throughout your vehicle, with symptoms that can include serious damage. If you notice the P0491 and P0492 codes in your vehicle, schedule an appointment with your local repair shop to get help with these issues.
How Easy Is It to Diagnose a P0491 Code?
The P0491 and P0492 codes can be exceptionally difficult to diagnose for hobbyists and other DIYers. This is because there are many possible reasons for the code, and the code isn’t well-known among those who have less experience with cars. If you’re experiencing the P0491 and P0492 codes, you should talk to an expert to get help with the diagnostic process.
How Difficult Is It to Inspect a P0491 Code?
Inspection can be just as difficult as a diagnosis for P0491 and P0492 codes. These codes are part of the SAI system, which probably isn’t part of the vehicle that you commonly deal with. It’s unlikely that you have a lot of experience with the inspection of this area in the vehicle, which is one of the reasons you should avoid the inspection yourself and get help from an expert.
Need Additional Help with Your P0491 Code?
In the case of the P0491 and P0492 codes, you’ll likely need help managing the issues arising from them. Instead of trying to handle the P0491 and P0492 codes yourself, you should talk to an expert who knows more about these problems and can give you insight into the issues you’re experiencing.
The first step in fixing problems in your vehicle will always be to find a repair shop in your area using the KBB store locator. A local repair shop is a great way to get the repairs you’ve been looking for without having to drive too far.
Additionally, the P0491 and P0492 codes will likely result in other codes indicating other problems. The OBD-II database will help you get more insight into the other codes you might see.
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