99 SLK230 Code PO410
 

I have a SLK 230 that has a check engine light on. The problem seems to be intermittant and hard to track down. I have performed the activation test thru my hand held and everything seems fine. I thought that since the problem seems to be intermittant that I would start by replacing a possible sticking diverter valve and the vacuum valve on the front of the engine. None of these items repaired the problem and the code keeps coming back. I don't know what else could cause the same code except a weak pump but when activated it brings the o2 sensor voltage down like it should and holds. I don't know whats next!! Thanks in advance of any help on this subject!!

I've had a handful of stubborn P0410 issues on M111 Kompressor equipped vehicles that I've fixed by replacing the re-circ motor. If the condition exists for a long enough period of time, it will eventually start setting fault codes that will lead you directly to it. Just make sure you don't have a "lazy" O2 sensor before you spend the big $$$ on the re-circ motor.

Thanks for the help. I will look at the wave form on the O2 sensor. Then I can better decide if it would need changing!! Would you happen to have the part# on the re-cic for future reference? I appreciate all of the help?

Did you ever get this problem resolved? If so what fixed it?

I have a very intermittent (like once every 3-4 weeks) P0410 that I'm chasing on a 2000 C230 Kompressor.

The strange thing is when I activate the air injection system for the first time the voltage on the pre cat O2 sensor drops to around 80-100 mv and seems to hang there. If I repeat the test a few seconds later the voltage drops like a stone to 20-30mv and remains there for the duration of the test and all subsequent activations during the diagnostic session. If I wait 15-20 minutes and repeat the process I get the same initial pattern - first activation "hangs" at 80-100mv with subsequent activations at 20-30mv.

I thought maybe I had a lazy 02 sensor on my hands but after looking at voltage output on the scope the waveform and response time are perfect - is it possible to have a lazy sensor in an extreme lean condition that performs well in normal operation?

Any leads/insight appreciated.

Tim

I haven't had any luck. The customer decided that the diagnostic time wasn't worth it!! Let me know if you find out anything!!

Yes, it's absolutely possible. I've seen it many times. The O2 sensor is often over-looked when diagnosing P0410 issues.

Don't worry about the wave-form. The thing you need to check is how the sensor responds to a lean condition. The test is quick, simple, and conclusive. All you need to do is monitor the sensor voltage. With the engine at operating temperature, hold the RPM at around 2,500. Wait until the voltage oscillates normally, then floor the accelerator for a split second and lift off. This will instantly trigger "decel-shut-off" (about as lean as it gets). The sensor voltage should drop like a rock. A healthy sensor will drop all the way to zero. Try this and post the results.

I had some free time today and generated the following results:

Using the test above I was able to get my 02 sensor voltage to drop to about 10-15 mv. In the first test it will drop to about 20-25mv and subsequent tests produce lower results - after 5 or 6 tests I'm getting down to about 10-12mv. It doesn't seem to go any lower than that no matter how many times I try the test. It's amazing how fast it drops, watching the pattern on the scope it falls pretty much instantaneously and holds lean for 3-4 seconds then switches back to rich for 2-3 seconds before stabilizing back to a sine wave pattern.

20-25mv isn't zero mv but it doesn't seem too bad, do you think its high enough to cause a problem?

I also spent more time looking at the actual waveform and it seems to be a bit lazier than I remember it being...... the sensor oscillates from lean->rich/rich->lean about 0.8 times per second. Sample 02 traces that I've seen seem to indicate it should oscillate 3-5 times per second.

If I increase the RPM to 2K (and presumably the temperature of the sensor) it will oscillate about 2 times per second. Looks like the hotter my sensor is the better it seems to perform.

Thanks - Tim

I decided to replace both oxygen sensors. With the new sensors in place I re-ran the test and I'm getting all the way down to 0mv when the throttle is released.

The 02 sensor waveform and cross counts are better (about 2 per second at idle) but I'm not sure this is going to solve my P0410 problems.

I'll keep my fingers crossed and let you know in a month or two if the P0410 reappears.

The new oxygen sensors helped but did not fix the problem, after six months and 10K miles my P0410 reappeared last week.

After further testing of the air switch over valve and recirculation motor showed no problems with either component I decided to remove the air injection check valve. Access to the valve is not easy and after about 45 minutes, and no success, I decided to try to remove the valve by removing the stainless steel tube that the valve is threaded into - the other end of this tube terminates with a connection into the engine block. From that point I'd guess the air is routed into the exhaust port via internal passages in the engine block.

At any rate removing the tube (with the check valve still attached) was very easy and in about 5 minutes I had the check valve and line on my bench - if you have to remove the check valve save yourself 40 minutes and just remove the tube/valve assembly.

The check valve and tube were 90% clogged by a black carbon based dirt/dust that had accumulated in the line between the check valve and the block. The check valve itself was also very clogged with carbon and soot - I'd guess there were at least 1-2 ounces of loose crap in the line and valve. Given the amount of junk in the line its amazing the air injection sytem worked at all.

I'm pretty sure this was my problem - but I'll update this post again if my latest efforts don't resolve this issue.

99 SLK230 Code PO410
 

I have been chasing this same problem on my SLK! I'm a shade tree mechanic at best. could you descibe this check valve and tubes location in more detail, or even post a picture of where it is so i can clean this puppy