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Old 10-11-2020, 04:57 AM
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Join Date: Oct 2012
Posts: 15
Secondary Air-Injection Check Valves Mod/Upgrade

So I have been running into the perpetual P0410 code on my ML320 for the last year or so and continue to look for a solution.
  • I have cleaned the manifold/hoses from top to bottom
  • Eliminated possible vacuum leaks with smoke test
  • Replaced the EGR
  • Replaced the Secondary Air Pump.
  • Cleaned the Air-Injection Check Valves and ports
  • Replaced the Air Injection Control Valve
  • Replaced the gasket around the intake pipe at the manifold opening and MAF.

I am starting to believe the issue is with our M112 and M113 Air-Injection Check Valves. Has anybody found a replacement or upgrade for these? It seems like these were poorly engineered and collect a lot of soot at the reeds, inside the openings and the check valve bell. It would be nice to find an upgrade to completely replace these.


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Old 10-12-2020, 01:05 PM
Senior Member
Join Date: Sep 2002
Posts: 2,878
One, or both of the upstream O2 sensors could be the problem. The sensor voltage should quickly drop to <100mV when the pump is running.....assuming the rest of the components are working. The system is pretty simple but you need to be able to look at some live data to figure it out.

Last edited by ILUVMILS; 10-12-2020 at 09:26 PM.
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Old 10-14-2020, 07:16 AM
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Join Date: Jun 2002
Location: Conway, SC
Posts: 318
When you say you cleaned the ports did you clean all the passages in the cylinder heads? What I have seen is the passages through the cylinder heads get stopped up and don't allow the air to be injected into the exhaust flow as designed. It usually requires cylinder head removal and sending them to a machine shop to be cleaned via long drill bits and solvent soaking tanks.

Like the previous post says though is you need to be able to monitor front O2 sensor values with the system operating and the values should drop quickly when the pump comes on.
Mercedes Benz Master Tech - Retired
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Old 10-14-2020, 01:07 PM
Senior Member
Join Date: Sep 2002
Posts: 2,878
The quickest way to check the sensors (assuming you can monitor the voltage) is to hold the RPM at 2000-2500, at operating temp. Quickly stab the throttle to the floor and then lift. This will activate the decel/shutoff causing a temporary lean condition. If the sensors aren't "lazy" the voltage will drop like a rock....

Last edited by ILUVMILS; 10-17-2020 at 06:07 PM.
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Old 10-16-2020, 11:48 PM
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Join Date: Oct 2012
Posts: 15
Thanks ILUVMILS and RPM55. I believe I have cleaned out all of the possible ports in the manifold leading to hoses and the ports leading to the check valves (in the cylinder heads). So I believe this issue is illiminated.

I also replaced Bank 1 and 2 upstream O2 Sensors, which I did not mention above. However, I have not perfromed the tests ILUVMILS describes above. I will try this and get back to you. Thanks for the help!

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