Part #1 P0491 check engine light? how to fix yourself Secondary AIR injection Diag VW Jetta

Secondary AIR Diag VW Jetta P0491 part #1 part #2 • P0491 Fixes for Secon... more diag tips for this problem
before you order the sensor and hose check for leaks in the pump or a blockage at the exhaust.
secondary air shut-off valve pressure
sensor with the hose: amzn.to/3UlZBe9
Great little code reader: amzn.to/3szwa8h
Power Probe 3 : amzn.to/3JwdUnJ
VW scan tool: amzn.to/49hIRZn
DISCLAIMER: This video and description contains affiliate links, which means that if you click on one of the product links, I will receive a small commission. This helps support this channel and allows me to continue to make videos like this. Thank you for your support!
This video is only for entertainment purposes. If you rely on the information portrayed in this video, you assume the responsibility for the results, some of the projects could be dangerous if not done properly. Andy the X tech

[@AndyTheXTech]

For part 2 that explains more and some easy free fixes. P0491 Fixes for Secondary AIR Injection VW Jetta Part #2 Easy Free Inexpensive kzbin.info/www/bejne/faW0qoaOeZyshqM

[@Surjnarine]

The air pump will only kick on at cold start ups. insufficient flow is usually loose hose, clogged passageways in the head from carbon or the pressure sensor. Your test at the fuse verified the circuit and pump was working.

[@kennysmith6824]

Great video! I needed this to help diagnose. We appreciate your willingness to make this video!

[@AndyTheXTech]

Thanks check for leaks and also carbon buildup. I will make a follow up video showing some other potential issues.

[@johne6081]

Good, clear, detailed video -- congrats. Viewers should note that older VW/Audi cars look for changes in the pre-catalytic O2 sensor reading, instead of a pressure sensor, when self-testing the SAI system. My own problem (2001 VW Passat 1.8T) was caused by a partially carbon-clogged combi valve, which evidently did not shut off all the way, and a leaky SAI control solenoid valve, which was not sending vacuum to the combi's control port. Fixing the first problem got rid of the check engine light, but it still wouldn't set the SAI readiness monitor until I replaced the second. My bad -- I could have diagnosed the problem a bit more quickly by unplugging the vacuum control line at the combi valve and testing for vacuum during a cold start.

[@collinhanson3802]

Your videos are so helpful. Thank you so much man!!!

[@AndyTheXTech]

Your welcome! This is why I make them. 👍

[@up458]

well done!

[@AndyTheXTech]

Thanks 👍

[@jsnichols1]

My 2010 is having this EXACT issue. Combi valve is clicking, fuses and relay are good but I can't hear the pump running. My next step will be trying a new sensor - thanks for this great video!

[@AndyTheXTech]

Also check out this updated video that can help. kzbin.info/www/bejne/faW0qoaOeZyshqMsi=ySof4isYkpYqlbNo

[@jsnichols1]

@@AndyTheXTech Awesome - thanks!

[@AndyTheXTech]

@@jsnichols1Your Welcome! Hope it helps. 👍

[@pavelsuprunchuk6473]

Waw smart dude!!!!!

[@patricktotten4359]

I have a 2018 B8 Passat with 206,000 miles on it and I’ve been throwing PO 491. The dealer told me I needed an 02 sensor and I needed a camshaft Cilla Noyd from a P11AD also, I took care of those issues in the only code. The snow going away is P0491 my mechanic told me the pump lower down below he goes that’s working, so does that mean I got a bad sensor or is that mean I have a leak in words that mean that valve is cooking open I’m gonna pay the dealer $162 to diagnose it for me and you were gonna tell me to fix the two issues now I gotta pay another 162 to see what’s wrong now.

[@Sheepdog34]

Hey Andy!! Thank you for this video. I’m not seeing a part 2 on your channel. Did the CEL stay off?

[@AndyTheXTech]

It did for a little while but then it had some more air pump issues. I’m planning on making a part 2 in the next week or so. Make sure you don’t have any leaks in the air pump, or hoses, and check for carbon build up on the exhaust side of the valve. There might no be enough flow.

[@Sheepdog34]

Thank you! I appreciate it. Turns out my 2.5 jetta had the updated sensor and hose. I found out the hose was disconnected at the air pump... sheesh @@AndyTheXTech

[@MMBenzo]

Hi all, can P0491 code have anything to do with shaky engine? No lights on dash, no misfires. The car is kinda laggy. When scanned with Vcds only P0491 code shows up. 1.6 mpi engine

[@ssinc.2065]

Having same issue with shaking.

[@alexanderprice5077]

I have a mkv golf i have this error alongside a fluttering sound under load. Same checks?

[@AndyTheXTech]

Maybe but probably not. Check for leaks. Also there could be a blockage from the valve to the exhaust.

[@PlayaHataz710]

Is it suppose to be that loud? Mine stays that loud for about 30 seconds it wasn't doing that when i first got the car

[@AndyTheXTech]

Sometimes they do get louder. I’ve noticed on older cars the pumps getting very loud. It could be something to do with the internals of the pump or even the rubber mounts for the pumps. But as long as there’s no leaks and the check engine lights not on it shouldn’t matter.

[@Rider-pv6yd]

There a way to test the pressure sensor before replacing it like you did? Thanks for the video too 👍

[@AndyTheXTech]

Your welcome. Yes if you have a scan tool with the correct data. There may be a way to bench test it but I’m not sure where you can find the specs. Another test you can do that I forgot to mention in the video is spray soapy water on the air pump and hoses. Then activate the pump see if there is any bubbles. If there is you need to replace that part. The pump housings some times leak.

[@Rider-pv6yd]

@@AndyTheXTech awesome. Thanks for the reply! I figured it would involve a high end diagnostic machine. I have a mid grade. All good tho

[@Rider-pv6yd]

@@AndyTheXTech I tested the pressure sensor for high resistance (engine off) and the voltage reference (engine on) using the voltage meter. Also was your pressure sensor the ultimate reason for the system failure?

[@AndyTheXTech]

@@Rider-pv6yd the Air injection system wasn’t working at all before I installed the sensor. Now the air system at least comes on. I did put a pump in it also because it was leaking. I do have a different code now so it’s progress. I just haven’t had time to mess around with it lately. I will probably update the video once I get a solid answer.

[@Just0ke]

I'm working on a vw new bettle 2.5 bpr. Secondary monitor won't clear. Bump works, valve opens and closes. Pump just won't come on. Does anyone know if the module monitors the ambient air temp sensor or the iat sensor to know its at a cold start? I know that it looks at ambient air and coolant temp to determine if it's at a cold start but I can't find any info if they use the iat sensor or ambient air temp. Anyone?

[@AndyTheXTech]

Ya that information is not easy to find. I’ll see what I can do.

[@jessequintino8539]

So if the air pump goes on, the sensor is good? I’ve replaced the Valve and Air Pump but P0491 is still there. I could hear the air pump at cold start- could it be the hose then?

[@AndyTheXTech]

There might be a blockage after the valve. Carbon build up.

[@jessequintino8539]

@@AndyTheXTech thanks for the reply! I’ll have that get checked out

[@glvryWorld]

@@AndyTheXTechWould the build up be in the EGR valve

[@CoolDansta]

I have a 2005 jetta with code p0411 the check engine light comes and goes whenever it wants but it doesn't have the sensor on the pipe

[@AndyTheXTech]

Ya it must use the 02 sensor to know if it’s working or not. Still the same concept. Pump, hose, exhaust valve check for air leaks.

[@CoolDansta]

@@AndyTheXTech idont understand how the kigjt comes and goesnfrommy testing. I tested the air pump by supplying 12v and it kicks on hard. Then I supplied 12 v to the valve and it clicks. The pipe looks fine and I checked all the fuses everything looks and sounds good

[@contrerasmiguela56]

What was the censor called?

[@hunterbaird235]

So I’m having the same problem but if I clear the code it’s stays off fir probably 30-50 maybe 60 miles then comes back on any advance before I start jumping into it ?

[@AndyTheXTech]

Check the air pump for leaks, I use Soapy water then activate the pump. Another thing is carbon build up after the valve. If it’s plugged not enough air can get into the exhaust.I’m going to make another video on it soon.

[@heatherlawson6874]

I'm having the same issue! Hence why I'm here. Lol

[@vocalone23]

So was it causing the car to rough idle

[@AndyTheXTech]

Nope has nothing to do with how the car runs. Do you have this code? I am making a better video that will explain more about the air system.

[@gstacks510]

Can you help I have a a 2009 jetta 2.5 s and I I don't have the SAI sensor or am I not finding it ? Does my car need it ? I can't get the SAI monitor to reset . Thank you.

[@AndyTheXTech]

You might have a different emission system in that car. It goes in between the battery and the valve cover of the engine.

[@gstacks510]

@@AndyTheXTech yes I've checked a couple of times it's not there. I tested the pump it works. I put soapy water on and around it and all the hoses and found no air leaks. So I don't know if I should just replace that combi hose or test the valve, that u haven't done yet. And btw I get no engine codes. I would just get a misfire randomly when I tinker with the car and put it back together. But I've driven 100's of miles since then and no code but the secondary air won't reset...

[@AndyTheXTech]

@@gstacks510 that’s kind of weird. Is there maybe a connector down there that is just hanging out? Maybe someone put a different hose on that didn’t have the sensor. I don’t think I would worry about it too much if you’re not getting a check engine light. Sometimes it takes a lot to reset all the monitors. Many driving conditions and multiple drive cycles. As far as a misfire I don’t think this is related. The air system only works for maybe 10 or 15 seconds when you first start the car and it’s cold. It has nothing to do with drivability just admissions.

[@gstacks510]

@@AndyTheXTech I'm not sure if someone replaced it with the wrong one . From what I can see there is no connector /wire harbess for the SAI sensor... so I'm really just lost... now I just tested the pump with the car off and some test leads... should I start the car and then test the pump like you did with the tester ? Does it make a difference? The relays and fuses seem to work.

[@AndyTheXTech]

@@gstacks510 No it shouldn’t make a difference.

[@alissiav9722]

Where are you located , I need a repair for the same code pleaseeeeee

[@aleKaneki]

Anyone in here thinking about getting rid of their vw and getting something else 😅? My 2015 vw passat 1.8 limited edition just dropped P0941

[@Our_America]

Me. I did everything i can't get rid from this P0491 fucking code. Thinking should i drive as it is or get rid from car. Can't even get inspection cause of this 🙄

[@alfonsogonzalez2099]

What year is this

[@AndyTheXTech]

2009

[@alfonsogonzalez2099]

@@AndyTheXTech mine is an o8 but i was wondering whats that piece you changed what is it called

[@AndyTheXTech]

@@alfonsogonzalez2099 the sensor with the tube. There is a link for it in the description. I’m going to make a part 2 because I’ve learned more information about this system. There could also be a leak in the pump or a blockage to the exhaust.

[@alfonsogonzalez2099]

@@AndyTheXTech thanks for the reply

[@alfonsogonzalez2099]

@@AndyTheXTech you know what i do remember my car doint the noise at the end of the video i never knew it was the air pump i dont hear it anymore but my both relays say 370 should i change it to same ones i might go to the junkyard tomorrow