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Secondary Air Injection Pump Troubleshooting Guide

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Since the early 2000s, emissions testing has become stricter, and rules on what cars can push out the exhaust have become fairly unforgiving. Car manufacturers have had to strike a unique balance between producing power and keeping emissions low.

Of course, this has led to many unique, complicated inventions. One of those being the secondary air pump and the secondary air system. 

Whether these are useful inventions is debatable, but they are here to stay. So as always, we’ll show you the ins and outs of these devices and how you can troubleshoot a secondary air injection pump should you need to. 

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Bosch Secondary Air Injection Pump for Mercedes-Benz

What is a Secondary Air Injection Pump?

The secondary air pump is indeed what you think it is. Your car has an air intake system that sucks air into the engine. A secondary air pump is an extra electric pump connected to the intake system. It feeds air into the secondary air injection system, where the magic happens.

What Does a Secondary Air Injection Pump Do?

The purpose of secondary air injection is emissions control. Yes, that is as exciting as it sounds. On cold starts, engines run a richer air-fuel mixture. There are many reasons why this is the case, including proper engineer warm up. 

However, this creates more emissions, which is not ideal. A large portion of your vehicle’s emissions during a drive come from the first few minutes of a cold start. Mainly because the catalytic converter only operates at a specific temperature.

The secondary air pump pumps air into the exhaust system, the air then reacts with the exhaust gasses. They combine to produce carbon dioxide and water, which is far better for the environment than pure exhaust fumes. Another byproduct of this reaction is heat, which helps bring the catalytic converter to operating temperature quicker.

It also only runs for the first 2-3 minutes on startup. If your pump is running for the whole drive, it could signify that your catalytic converter has failed or the pump itself is faulty.

What Happens When the Secondary Air Pump Fails?

secondary air injection pump bosch

A secondary air pump failure will not be the end of the world, simply because it is not the main air intake. Of course, it can lead to power loss, idling issues, or stalling during cold starts. Pump failure will also affect the emissions output of your vehicle.

The low engine idling and stalling are caused by the ECU (engine control unit) adjusting for air changes caused by the leak or blockage. This is more likely to happen when you stop your car or right after you start it, rather than in the middle of a drive, so it will not result in a dangerous situation.

If your car has a turbocharger, it is uniquely susceptible to power loss because of a failure of the secondary air injection system. Exhaust gas powers your turbo, so any leak in the exhaust or the secondary air injection system will affect it.

Causes

One of the major issues with the secondary air injection system is moisture and the combination valve rusting. The valve prevents exhaust air from coming back into the secondary air injection system, so that the pump is not damaged by high pressure or heat from exhaust gas.

The issue with this valve is that it doesn’t prevent moisture from entering the system, and the chemical emissions reaction produces water. The combination valve can end up rusting, and the pump can seize due to rust buildup.

This issue is all over the place in the earlier iterations of these types of systems, usually early 2000s vehicles.

The pump itself can fail. The plastic can become brittle and deform because of changes in temperature and the heat of your engine. The rubber hoses can also leak air if there are cracks, or if they are loose.

There are many ways of testing if these parts are faulty, and in the next section, we’ll delve deep into them.

Troubleshooting a Bad SAIP

The secondary air injection pump isn’t a complicated device. Aside from being fairly robust thanks to its design, it’s also pretty simple to diagnose. Here are several ways you can tell if your SAIP has gone bad! 

ODB II Reader

The first item on your checklist should always be to plug in your ODB II reader. Once you see the check engine light code on the dash, reach for your reader as soon as possible.

You can check for any stored faults in the log. If there are no faults, you can test your pump using the actuator test mode. It allows you to test whether it is opening and closing like it should.

The error code you should look out for is P0410. A code like this can also mean that your o2 sensor or catalyst has failed, so it doesn’t point directly to your secondary air injection system failing. Although, It will bring you closer to diagnosing the fault.

However, a secondary injection system failure is the quickest system to check, so it should be checked and cleared before moving on.

Ear test

Your ear is also one of the best tools for diagnosing car problems. A failed pump sounds similar to a coffee grinder running alongside your engine and will wheeze and become louder if you rev your engine.

Another acoustic method of finding leaks is to listen for faint whistles and follow the sound to track air leaks down. Just make sure you’re pumping air into the system, whether that be by running your car or by using a vacuum pump.

Vacuum test

A vacuum test is always useful for diagnosing any air system issues. You can purchase a manual vacuum pump for next to nothing and if you’re not interested in manual labor, an automatic will also work.

If your vacuum pump is at the ready, here’s how to use it. To see if the secondary air injection pump has failed, hook it up to the control valve hose fitting and start your vacuum pump. If the pressure is low or fluctuating, there is a leak.

Testing the combination valve is a similar process. The combination valve (kombi valve for German cars) is a small valve that controls airflow at the end of the system. To test it, remove the vacuum hose from the combination valve, and then connect and run your vacuum pump.

The same method works for rubber hose leaks as well. Your first instinct should be to look for damage on the hose and damage where the hose clamps are. Most hose leaks happen where the hose is bent, areas where it could rub against another part or at the fittings.

Inspection test

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If you don’t have a vacuum pump on hand, You can hold your hand near the secondary air injection pump while the car runs to see if air leaks through the seams. As long as your car hasn’t been running for too long, it shouldn’t be too hot as this air is coming fresh from the intake.

Another method is disconnecting the secondary air pump and inspecting it for damage. Look for any signs of melting or if the pump smells burnt, both those signs mean the pump needs to be replaced.

Fuse, and Relay Test

Fuses and relays tend to be high failure components, they are cheap to replace and cheap to produce. They tend to cause minor malfunctions rather than breaking essential components, and they are easy to test.

The fuse or relay of your control valve can be at fault in this case. You can test this by using a multimeter. First, disconnect the wire harness connected to the system. At this point, you need to make sure your car is on so that there is electricity flowing through the car.

Once you’ve done that, place the red and black multimeter probes into the small wire harness, making sure they make contact with the metal. Your control valve needs replacing if you measure a tiny amount of voltage or none at all.

DIY repairs

We know that you love working on your own cars, so here’s what you can do to fix the issue. Start by replacing seals, hoses, and clamps, but 6 hours later, the system is still leaking air.

The pump is exposed to a lot of heat from the engine. For most steel and aluminum parts of your engine, heat is manageable. The cooling system makes sure there is always oil or air flowing through them, mainly based on the priority of the part.

The secondary air injection pump is an afterthought in most cars. Most manufacturers use weak plastic that melts and deforms under heat, and no heat shielding for the pump. We love DIY fixes, but replacing an inner seal or using duct tape will not work for this one.

More often than not, you’re looking at a replacement of the unit. The key here is to use a quality replacement part that will bring you the same quality and reliability as the part that came with your car. Something like Bosch 0580000025 is a great choice for those who drive recent model Mercedes vehicles. There are similar solutions from Bosch for other brands as well. As long as you use OEM grade SAIPs, you should be fine. 

Can I Drive Without Secondary Air Injection?

The secondary air injection pump is not needed to start or run your car. You can remove the pump and the system altogether, and as long as there are no air leaks, your car will run peachy keen.

However, if your state requires regular emissions testing, which most states do, your vehicle won’t pass. Additionally, unless your car is older than 15 years, you won’t be able to drive it.

Some cars can run with a pump failure of this nature, only increasing emissions output and leaving your check engine light on. However, It’s always up to you to decide whether your pump should be replaced. The pump is an expensive part in some cars.

Get Quality Parts For Your Car

For this issue, the most straightforward solution is to replace your broken secondary air injection pump if it’s at fault. Here at eEuroparts.com, we offer all the parts to replace your pump and more.

It’s as easy as selecting your car’s year, make, and model, and that will give you a complete list of parts that are a guaranteed fit for your vehicle. 

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2 thoughts on “Secondary Air Injection Pump Troubleshooting Guide

  1. So I had a dead bttery for some time and when replaced all my sensor lights turned red but NO CEL. Over a short period they all cycled into green except the “AIR” on my 2000 boxter. Seems to me if there was a physical problem with any of that system it would throw a CEL light. Again no light just a red “air” light as though not cycled yet but functioning properly. Any thoughts?

  2. This was helpful so checked out sys my problem is Ecm is not supplying the ground scan tool showed air off doesn’t change.was looking for what conditions need to be met to make work no other codes

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