What Does the Secondary Air Injection System Do?

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Implementation of the Secondary Air Injection System (SAIS) on Toyota Trucks and SUVs did not start until model year 2005. That said, if your Tundra is 2004 or older then consider yourself lucky. You do not have to worry about this system. However, for everyone else the question is not "If" the SAIS will fail but "When" will it fail!

The following includes details from our Blog "What Is The Secondary Air Injection System?". We hope this information will help you better understand the failure prone system and if you have any question do not hesitate to contact us on the forum or through our website.

Introduction:
The Secondary Air Injection System (SAIS) is part of a vehicle’s exhaust system. Manufacturers began introducing it in the 1960s to help reduce hydrocarbon and carbon monoxide emissions, both of which resulted from incomplete combustion. Toyota and Lexus SAIS systems are only commanded to operate after a cold start, which is when the engine has been sitting for at least seven hours.

The SAIS injects oxygen-rich ambient air into the exhaust manifold downstream of exhaust valves. It does this for approximately 30 to 90 seconds to allow the engine to get to operating temperature. The SAIS then shuts off.

What Is The Purpose Of The Secondary Air Injection System?
It’s no secret that gas-powered engines aren’t 100% efficient. As a result, there is a portion of unburned fuel (hydrocarbons) that doesn’t get converted to engine power. This is particularly true on cold starts for two reasons. First, for more reliable starting, the fuel/air mixture is going richer in fuel. Secondly, it takes a couple of minutes for the engine and catalytic converters to get to operating temperatures.

These two factors combine to increase the amount of unburned fuel after a cold start. Thus, the purpose of the secondary air injection system is reducing hydrocarbon and carbon monoxide emissions that result from cold start conditions.

Please clink on the Link above to continue reading about...

• What Components Comprise The Secondary Air Injection System?
• How Does The Secondary Air Injection System Work?
• Can You Drive Without The Secondary Air Injection System?

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Additional Secondary Air Injection Resources
To learn more about SAIS solutions or SIAS fault codes click on the following “Must Read” Hewitt Tech Threads:

- What Do my Secondary Air Injection Codes Mean?
- How to Fix the Secondary Air Injection System?

***Spoiler Alert - Don't Use Aftermarket Parts***​

Disclaimer
It is illegal to remove, dismantle, or otherwise cause to be inoperative any pollution control device required by federal, state, or local emissions law. No other applications are intended or implied.