mcole01

Hello,

I'm a new member and I have a P410 code on my 2006 SLK 280. My mechanic checked the secondary air injection system and he tells me that everything checks out OK. The air pump runs when 12 volts DC is placed across the terminals and it's receiving the correct voltage via the relay. My mechanic suggests that, although the pump is running, it may not be pumping sufficient air i.e., it's operating at less than its full capacity. before I spend ~ $600 on a new air pump can you confirm that this is a possible cause. Isn't an electric blower motor either running or not. Can it run at less efficiency? It seems to be blowing quite hard to me.

I purchased a used air pump off a 2008 SLK from a recycler and installed it but the check engine light came back on again, so I'm lost as to what to do next.

I'd appreciate any advice.


Best,

Mike

paulv

The SAI systems usually have one or more shutoff (switchover) valves (1 or 2 cylinder banks), a check valve (for intake manifold vacuum), and of course, the pump.

Another issue that can happen is the SAI feeds into the exhaust can get clogged up and need to be clean (a real PITA job!).

When your mechanic said "everything" did he check all of that stuff too? Measuring the voltage across the pump terminals is only part of the test -- you will need to see how much current the pump is drawing. When measuring the pump voltage, measure the battery voltage first, as the pump voltage needs to be within (usually) +/- 0.3 volts of the battery. Same story for the shutoff (switchover valves).

It's time to source/purchase some service info for your car...............

Regards,
paul...

mcole01

Paul,

Thanks. I very much appreciate your advice. The check valve and the relay were replaced and the shutoff valves checked out OK. I'm not sure he checked the SAI feeds into the exhaust. I'll ask him. Is there a test that would implicate the feeds into the exhaust?

All the best,

Mike

paulv

There really isn't any test -- however the air feed that is routed into the exhaust has to be checked for clogging, etc. I don't know how MB does it -- some cars have air lines going into the exhaust manifold -- your mechanic should know this. The problem is that it's going to require a good amount of disassembly which equals $$.

Does your mechanic have the MB scan tool (or something similar like Autoenginuity) which he could activate the components or did he just apply a battery source to them? To isolate the pump as the problem, you will need to check the voltage/current values when the pump is running, but I don't have the factory values for these -- this is where the MB service info is required.

Has all the wiring been checked from the PCM to the components? Corroded wires will change the voltage/current values at the component.

BTW, the P0410 is for the entire SAI system, and the code is set when the PCM "thinks" the SAI system is failing. There could be an external (to the SAI system) issue that could be causing the problem since the job of the SAI is to provide fresh air into the exhaust to oxidize excessive HCs when the engine is cold (and running rich) or when idling (some times will run rich).

Regards,
paul....

mercedestech77

There is a DTB regarding the secondary air injection system but does not mention that specific code. DTB # S-B-14.30/15f... If the pump is coming on and the relay is good I would replace the check valve. When looking in the area of the sencondary air pump you eill see a vacuum line and in the middle is this little blue piece. That is your check valve. Hope this helps.

paulv

I've read that DTB but it sounds like his mechanic already tested all those items so I didn't bother to mention it. I'm only a DIY'er and have run out of ideas to try and help this guy. Do you have any suggestions that could help him?

Regards,
paul...

Ausmbtech

OK. back to basics.
Start by checking that the air pump turns on after a cold start and check the voltage at the pump. it must be over 12v.

Now check that the air hose to the air filter housing isn't crushed and is properly connected.

Check that the air injection valves (2 of them) can be operated by using a vacuum hose and a mityvac/suck on the hose.

If the air pump, air line and injection valves are all ok then you may have a blocked air injection duct (very unusual).

If you have any fault codes relating to the o2 sensors then you must deal with them first. Have you added any exhaust headers or made any exhaust related changes?

paulv

Helped another guy with this problem and it turned out that the Front Driver's side SAM unit failed.

The PCM sends a signal to that SAM which has a relay to turn on/off the SAI pump. There's also a 40 amp fuse in that SAM between the relay contacts and the pump.

Regards,
paul...

amcink

Where and What is the SAM unit

amg305

Sam is short for a Signal acquisition module. there are several on different parts of the car . Left front is where you need to look. 40amp fuse is a big and orange

chazman

So, what's the outcome of this episode?

My coworker's 2006 SLK280 had a check engine light coming on. Took it to an authorized MB dealer and they charged $600 for replacing the faulty air pump relay failure. Then 2 days later the check engine light came on again, and took the car to the same dealer. Now they are saying the fuse box failed, contact burnt out inside the fuse box that controls the relay. And now they are charging another $800+ for the parts (complete new fuse box?) plus the labor. They are saying that faulty relay caused the fuse box contact to burn out (or vise versa?).

Which one do you think failed first?

Air pump is covered under the emissions warranty, but dealer says air pump relay and the fuse box are not (even though only the component that controls the air pump relay has failed). ???

Does anyone have any experience on this kind of repair?

I'd appreciate any input or advice.

Thanks in advance.

Holmes5518

The relay got stuck open and the constant load melted the pins on the fuse box. It is indeed necessary to replace. It's a simple job, just pay attention to details.


To the original poster, you need to monitor the voltage output of the oxygen sensors while the air pump is running. They need to drop way down to less than 30mv (I think that's the value) while the pump is running. You likely have clogged secondary air valve or pipes around the cylinder head.

alexoE55

What does that pUmp actually DO?! and can you create damage if you do not change it over time...