Check Functionality of Secondary Air System

In a gasoline engine, many harmful substances are formed, especially during cold start (when a very rich mixture is needed, meaning excess fuel): blowing secondary air directly behind the exhaust valves into the exhaust manifold significantly reduces these emissions. The secondary air system consists of a pump (located near the windshield washer fluid reservoir) and a check valve that prevents exhaust gases, condensation, or pressure spikes from causing damage inside the secondary air pump.
The most common malfunctions of the secondary air system are: noise from the secondary air pump or its failure to operate. If this occurs, it means that exhaust gas condensation has entered the pump due to a failure of the check valve: therefore, in case of anomalies, always check all components.
To check the operation of the secondary air pump, you can disconnect the plug and power it directly (but for no more than 90 seconds, as the pump is not designed for continuous operation): if the pump does not work or operates making scraping or whistling noises (like a vacuum cleaner), it must be replaced.
The operation of the check valve can be tested with a manual vacuum pump in the disassembled state (disconnect the flexible hose connecting the secondary air pump and the valve): if the valve does not open when vacuum is applied, it must be replaced. Additionally, if the vacuum applied with the manual vacuum pump decreases, the valve membrane is not sealing.