[khlam]

2016 0.9L Turbo DCT. Check engine light is on and the code is P0491 (only one code is showing).
I did not notice anything unusual. I.e. start with no problem, engine runs fine, etc. I mostly driving on local streets (~45mph)

Anyone ran into this error before?
What could be the likely cause?
Any suggestion on how to diagnose this problem?
I.e. where do I begin...

Thanks

 

[khlam]

Here is the failed test as reported by the app runnig on my Android head unit.
I have a bluetooth OBD2 reader plugged in the car all the time.
Now I have to find out what is causing the failure.

 

[vadsoom]

I’m thinking that the air injection pump is failing or the fuse has blown. It’s a high-current fuse (40A if I recall). For troubleshooting, I would look from the load side of the fuse to ground. It should read low ohms, bit not zero though the smog pump windings. If it’s zero or very close to zero, the pump should be replaced. If it’s higher ohms, (I’m
Thinking above 15 ohms or more), you might get away with just replacing a fuse.

Let me know what you find.

 

[khlam]

Great suggestions. Thanks
Found the fuse box diagrams for our beloved 453: Fuse Box Diagram Smart Fortwo / Forfour (W453; 2014-2019)
I believe you're referring to the Rear Fuse/Relay Module: fuse #9 (60A).
Now I have to figure out how to get to it... I will try to troubleshoot it this weekend

 

[khlam]

Still in "keyboard mechanic" mode as I won't have time to work on the car until weekend.
Looks like it could also be the Changeover valve (aka Switchover valve). Part number is "A 002 540 70 97". But it is also listed as "002-540-70-97-SMART".
Internet search of that part number return many matches but for different car models (price ranged from $35 to $60).
Anyone knows where this part is located in 453 engine bay (left, right, front, back, under?)
I want to take a few pictures to see if it matches the listings online.
Image from ebay (Smart Fortwo is NOT in the compatible list but the part number matches)

 

[khlam]

Update:
After several more short trips after seeing that CEL, weekend is here.

No problem with the fuse and on cold engine start up, I can hear the noise from the air injection pump running for a short time (about 30 seconds)
That mean the air injection pump is working just fine, right?

Look around the engine but couldn't find anything that looks like the Changeover Value pictured.
But the good news is that, this time, I was able to clear the code with the Android app.
Now the CEL is off!
Some kind of glitch? I guess I have to wait to see if this code will come back.

Sorry, false alarm...nothing to see here.

 

[jwight]

That changeover valve is for a 451...

 

[khlam]

That changeover valve is for a 451...

Really? May be they are using the same part? Then again, what do I know...
I got the part number from here "A.I.R. System for 2016 Smart Fortwo | MB Online Parts".
But the picture is from internet.
Rock Auto also list the same part number for 453...

 

[khlam]

By the way, if anyone knows where the Changeover Valve is located (453), please let me know.
Thanks.

 

[khlam]

Still trying to locate the Changeover Valve or the Secondary Air Injection pump.
So I am throwing out some pictures to see if someone more knowledgeable can chime in and offer some insights.

Start the engine in a cold morning with engine cover off to see if I can locate the Secondary Air Injection pump.
The pump is quite loud and will stop after a short time.
The sound is coming from the right side but I cannot pin point the exact location where the noise came from
It is somewhere from within yellow rectangle area

Closer view of upper-right corner, right next to the alternator.
Pump sound seems to come from this corner (not sure what this is, but any guesses are welcome)

There is also a "pump like" device underneath the motor-oil filler cap with limited access.
It has some small hoses attached to it.

 

[khlam]

The plot thickens...
Managed to find this diagram online about some "air pump system" on 453.

The "air pump" (#300) looks very similar to that thing at upper-right corner. See picture 2 in Post #10.
The "Exhaust Gass Valve" looks similar to picture 3 in Post #10
But I still cannot figure out where Changeover Valve is located...

300 AIR PUMP 001 A 00 014 069 85
420 EXHAUST GAS VALVE 001 A 00 314 001 60
570 CHANGE-OVER VALVE 001 A 00 254 070 97

 

[khlam]

I think I had mapped out the major component locations of this "Secondary Air Injection" system in 453.

These hoses seem to match #550 in the air pump system diagram and they lead back and down behind the engine.

Thus, I have to crawl under to check (car raised on rams). Found the Changeover Valve!
Right above the oil filter (about 10 in. up). Space and visibility is limited but accessible (one hand).

Mystery solved with a sense of accomplishment.
So if 453 owners run into issues with "Secondary Air Injection system" in the future, you know where to look.
Of course, these are just my own guesses and opinions. Use at your own risk.
You are welcome.

 

[romanb8]

I think I had mapped out the major component locations of this "Secondary Air Injection" system in 453.

These hoses seem to match #550 in the air pump system diagram and they lead back and down behind the engine.
View attachment 68564

Thus, I have to crawl under to check (car raised on rams). Found the Changeover Valve!
Right above the oil filter (about 10 in. up). Space and visibility is limited but accessible (one hand).
View attachment 68565

Mystery solved with a sense of accomplishment.
So if 453 owners run into issues with "Secondary Air Injection system" in the future, you know where to look.
Of course, these are just my own guesses and opinions. Use at your own risk.
You are welcome.

was there a third hose connected where the clip is? thanks to this i was able to find mine been looking for 3 months, but as i felt it i noticed no hose where the power clip is.

 

[khlam]

was there a third hose connected where the clip is? thanks to this i was able to find mine been looking for 3 months, but as i felt it i noticed no hose where the power clip is.

As far as I know, no hose is connected to that side. Could be just a vent outlet.