The secondary air injection system is an emissions system equipped on many road going vehicles. It is composed of several components that work together to reduce the vehicle’s tailpipe emissions. One of these components is the air pump check valve. The air pump check valve is the valve that allows air supplied from the air pump to be pumped into the exhaust stream to reduce hydrocarbon and carbon monoxide tailpipe emissions. It functions as a one-way valve, allowing the air to pump through into the exhaust, while preventing the exhaust fumes from leaking into the secondary air injection system.

When the air pump check valve fails, it can lead to a variety of problems, notably a significant increase in the vehicle’s tailpipe emissions. Usually, when the air pump check valve fails, it will display a few symptoms that may alert the driver of a potential problem that should be inspected.

1. Exhaust fume odor

One of the first and most common symptoms of a bad or failing check valve is an exhaust fume odor. The odor is a result of exhaust leaking either from the valve housing, or through the actual check valve back into the secondary air injection system. The odor may become most noticeable at idle speeds. Any sort of odor indicates an exhaust leak, which compromises emissions.

2. Failed emissions test

Many states require their road-going vehicles to pass an emissions test in order for the vehicle to be legally operated. If the air pump check valve fails, it can significantly impact the tailpipe emissions of a vehicle. The air pump check valve works to reduce hydrocarbon and carbon monoxide emissions of a vehicle, so when it fails, the levels of these two pollutants will increase.

3. Check Engine Light is On

Another common symptom of a failed air pump check valve is the Check Engine Light coming on. When a problem is detected by the vehicle’s computer, it will set off a code and activate the Check Engine Light. Having the vehicle scanned for trouble codes can reveal if there may be a problem with the air pump check valve that needs to be addressed.

As the air pump check valve is part of the vehicle’s emissions system, is it is very important that it functions correctly so that the vehicle can remain at acceptable emission levels. If you suspect that your air pump check valve may be having a problem, or your Check Engine Light has come on, have the vehicle diagnosed by a professional technician, such as one from YourMechanic. They will be able to determine if the vehicle needs an air pump check valve replacement, or if another repair needs to be made.

This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Air Pump Check Valve and was authored by Ed Ruelas.


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