Jefri Yahya

Hi all,

I know there's a lot out there on this fault, however nothing seems to help my situation.
With illuminated engine CEL light, diagnostics on Carly revealed below.

"Motor Electronics (-):
- : Fault: B16 (Right temperature sensor upstream of NOx storage catalytic converter) The NOx sensor (cylinder bank 1) has a malfunction.
- Code: OBD 03 P0410
- : Fault: B16 (Right temperature sensor upstream of NOx storage catalytic converter) The NOx sensor (cylinder bank 1) has a malfunction.
- Code: OBD 07 P0410"

I replaced the right forward NOx sensors because there was an instant when the right forward NOx sensor was faulted, but motherless the defect persisted, which is to reappear after every 100-150km or so.
On morning start and initial idle, I can hear the louder note from the engine for about 30secs. The sound of which sounds like the manifold and that Vee 8 rumble makes, more evident.
Part of my following test was to connect 12v to the blower. Operates nicely without noise indicative of bearing issues or a dragging motor. Also removed the air control valve, right side only, to look into the manifold porting for carbon build up or any constriction. That looked clean actually. Using a mity Vac, I ops checked the air control valves to see whether it would open with vacuum. It did as I also checked to make sure that flow through was indeed available, when the vacuum air was supplied to raise that valve open.
I inspected the small muscle air rubber hoses as well as the larger rubber hose from the blower to the two air control valves.

I'm still baffled as the issue still occurs.
My question is, how does the secondary air system detect that there is a malfunction. Is there a temp sensor looking at the operation of this thing on a 2006 w164 ML500.
Note that I have only looked at the right side, because the diagnostics only faults the right side (aft looking forward). I am also ignorant of this right side temp sensor on this w164 it keeps faulting. No idea what that looks like.

Cheers everybody for any ideas.

Maj. Dundee

Throw that Carly code reader away. It's already cost you the price of an O2 sensor that you did not need.

Code P0410 refer to the AIR Pump located on the front top of the engine, if that is actually the problem.

I suggest strongly that you buy a scanner that will read and clear every code in every module in the truck.

Jefri Yahya

Thanks Maj. It works fine on VAG. But not quite there for Mercs. Thanks for the link also. Gonna scope them out

Jefri Yahya

Hi all,
Whilst on the topic of diagnostics, any one familiar with this system. Would it be detailed enough to come close to MBstar system, albeit without the updates

Maj. Dundee

W164 chassis has 43 modules that have to be read. Make sure this scanner can do so.

Jefri Yahya

Latest development on this issue. Left the front engine cover removed, so as valve operation would be more audibly evident.
And behold, found that the right valve would open even when engine was warmed up. I was reversing into my garage, so car was idling at the time, & heard the familiar manifold note, usually heard during cold start. Immediately that same time, the Engine warning light came on.
So here's what I understand. Both Check valves are spring loaded shut. Vacuum is needed to open them. Vacuum muscle to both are available when the single Solenoid change over valve is energised, hence allowing for muscling the check valve to open.

I have tested the left valve operation in previous test, & confirmed that the computer can differentiate which side is malfunctioning. Basically I was able to make computer fault the left side by vacuuming the left check valve open when engine was warmed.
So since left was never the issue to begin with, I know now that the fault detection is indeed real now with the right side, as faulted by computer and being able to audibly hear the opening of that valve, and getting the CEL immediately after.
My question is now,
1/ If the Solenoid change over valve is faulty, why didn't both Check valves open.
Is is because the shorter vacuum line to the left valve made in more responsive to the intermittent opening of the change over valve?

2/if I plugged the vacuum supply to the change over valve, would I get a CEL for this. Reason I'm asking is to understand if I can trouble shoot it by confirming that indeed the intermittent opening of the changeover valve was causal for the CEL.
And am I gonna do any damage to the engine/CAT by driving it this way. ( I understand that I won't get Air enrichment during cold starts, & that emissions would be elevated during this cold start up)

Cheers all

Maj. Dundee

It's not the valves that are the issue. The problem is, one or both exhaust ports below the valves are clogged with carbon.

Working with a cold engine, remove the large hose and the small hoses going to the shut off valves. Then remove the single bolt that holds the valve to the manifold. Remove the valve and the metal gasket. DO NOT LOSE THE SMALL BOLTS.

Start the eng. and place your hands over the open exhaust ports and determine which port/s are clogged.

Replace everything and post back with results. And no, there will be no damage to the eng. by running it this way.

Jefri Yahya

Delayed progress on car as only just returned from Korea this dawn.
Removed both valves, and found both ports on manifold blows out hot air. ( Initial starting sound was quite a shocker though)
With both valves out, decided to test both valves for opening. No problems there. It was when I tested them for the Check function that I notice the right valve can allow air through if I blow lightly, as oppose to blowing thru harder.

Disassembled the valve and found that the thin reed was gapped and not seating fully.
Tried to unscrew the thing, and both the darn screws sheared off. So had to drill them out, & install new screws.

So that's what I did today. I'll see how it goes thru the next couple of weeks.


Also any one knows what this thing is about. Located right next to the solenoid control valve

Jefri Yahya

today it happened again. But this time I was right at the engine that was idling with the hood open. This time I immediately removed the hose to check if there was vacuum being supplied. And wallah, there was. It was supplying vacuum whilst the engine was already warmed up. It did so for about 5-8 secs then stopped.
The thing is, only the right valve was opened because of this. I guess the opening actuator on the right is more easier to open than the left.

So my take is, the solenoid is leaking or is getting spurious signal to open when it shouldn't. But then again it didn't open wide enough to activate both sides. So I'm ebbing more towards thinking that the solenoid control valve isn't stopping the vacuum well enough.
Leaky solenoid control valve? Weakening spring in the solenoid control valve? Seems the problem occurs when the engine is all warmed up. Doesn't quite happen when I'm happily cruising away. Last occurrence before was also when rpm was low, as I was reversing car back into the garage.

Maj. Dundee

Indicate by using an arrow.

Jefri Yahya

Jefri Yahya

The black valve I suppose is for the inlet manifold to control airflow length.
But the small sensor looking thing, I haven't a clue what that's for

Maj. Dundee

The first photo left is the MAP Sensor. The other photo I have no idea, cannot make it out.

Jefri Yahya

Thank you Sir

Anyway it was actually quite easy to troubleshoot the control solenoid sensor in the end. Simply Disconnect the vacuum line off from the two check control valves and plug them, & problem doesn't reappear.
For good measure, one can leave vacuum connected on one of the valves each time to also check operation off individual valve operation. And what I found was the right valve seems to be open easily whenever the solenoid control valve leaks vacuum through itself.
Ie it opens intermittently and supplies vacuum when it shouldn't ie when engine is already warned up.
With having them vacuum lines both disconnected & plugged, no more issues.

However thing is, even with cold engine now, the system doesn't detect that it doesn't get the additional manifold air supply that is used to warm them CATS faster. I guess that's not detecteable apart for probably a higher emissions during that cold start cycle.

Here in Brunei, ambient temp is generally 30 degrees Celsius above all the time. Dono if this system is worth keeping activated, and whether emissions is really of any consequence.

Also I don't imagine any danger to them CATS leaving it in this configuration. They would just take a tad longer to warm up to operating temp.

Is my understanding here flawed?

Maj. Dundee

So basically what you are saying is that you want someone to agree with you.

Jefri Yahya

Yup. Are my assumptions correct, or am I totally confused in my understanding?

Like I said on the last sentence, Is my Understanding flawed?

Maj. Dundee

What I don't understand is why you no not want to fix the problem? You seem to be satisfied with removing the vacuum lines to get rid of the code.

Yes, it's flawed if you don't care about how the eng. should run.

Jefri Yahya

Ok. I understand now Maj. It is imperative that the secondary air supply remains operative. I am just trying to get my head around what it actually does. For my current limited understanding, it just seems to pump inlet manifold air into the exhaust for some 4-8secs during cold starts and then remains off for the rest of the duration. This confuses me to as what the system hopes to achieve.

Anyway thanks for all your help Maj. Must be tiring being the resident expert on w164 and having folks like me nag for some more of your knowledge.

Do appreciate your relentless help.