Check Engine Error P0410

2002 Mercedes SLK 230
(R170 Chassis)

At 40,000 miles, my Check Engine light came on — sad.  The error code was P0410: Secondary Air Injection System Fault.  Secondary air warms up the catalytic converter by diverting air from the kompressor.  This happens for the first 150 seconds of cold engine operation.  (Other cars have a separate air pump.)

In my case, it was caused by a defective check valve (002-140-68-60), which was rusted shut.  This valve keeps a backfire from reaching upstream to the air valve (002-140-55-60) or other components.

I found a web picture showing the location of this valve on a 1998 SLK, but it’s in a different place in my 2002 SLK.

002-140-68-60 check valve
002-140-68-60 Check Valve. Cause of my P0410 Check Engine Code.

Replacement: It was a nasty problem getting the old valve out.  It’s threaded into a stainless steel pipe and has a 27mm nut on the bottom.  The problem is that 40,000 miles of heating and cooling from the exhaust has baked the two components together.  What’s worse, the 27mm nut requires an extra thin open-end wrench, which I couldn’t find.  I ended up sawing the old valve vertically down to the nut and peeling it apart with vice grips.  Then, I could unscrew it with a 1 1/16 inch socket from the top.  Screwing the new valve on was easy.

P0410 Again: I got the P0410 error code again at 65,000 miles.  This time, I found the correct (thin) wrench at Hall Tool Company in Portland.  It’s a 1 1/16 inch Thin Pattern Pump wrench from Armstrong (28-034).  It was nice of the guy at the tool company to write “27” on it, so that it would feel welcome under the hood of my SLK.  This wrench is only 7 inches long, 1/4 inch thick and fits into this tight spot.  I used a pry-bar against the transmission housing to apply enough force to loosen the valve.

Armstrong 28-034 27mm wrench
Armstrong 28-034 27mm wrench for removing Mercedes 002-140-68-60 Check Valve

After only 25,000 miles, the check value was not rusted shut.  I installed the new one, but error code came back after 2000 miles.  I removed the intake hose from the air valve (002-140-55-60), started the engine and noticed that there was almost no air coming out of hose.  It was time to take the car to Mercedes.

The dealer (sadly) started by cleaning out the stainless steel pipe at the exhaust manifold connection (“moderate carbon build-up”) and replacing the pre-cat O2 sensor.  That didn’t fix it.  On the second try, they replaced the 111-098-00-50 Recirculating Air Flap, which fixed the problem.  It’s located at the air filter housing:

Mercedes 111-098-00-50 Recirculating Air Flap
Mercedes 111-098-00-50 Recirculating Air Flap – cause of my P0410 Check Engine Code

Here is what my old part looks like — same as the throttle body on the intake manifold.

Mercedes 111-098-00-50 Recirculating Air Flap
Mercedes 111-098-00-50 Recirculating Air Flap

The replacement of this part has fixed the problem. It also restored the full power of my engine. Let me know if this part caused a similar problem on your SLK.

Updated: January 2017
Contact: Hoeren at Comcast dot net