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P0411, hose replaced...bad combi-valve/air pump?

143K views 57 replies 24 participants last post by  wobcc1722 
#1 ·
The CEL on my 2000 1.8T came on a few weeks ago. Pulled P0411 (Secondary Air Injection Incorrect Upstream Flow Detected ) from the computer. Checked here and found that it could be the vacuum hose, combi-valve($$), and/or the pump($$$).

I replaced the hose, which looked suspect, cleared the code but it came back after a few days. I don't think the pump is coming on any more after a cold start (used to be quite noisy, IIRC). If the pump is not coming on any more, it would mean a dead pump or blown fuse, right?

Some questions:

1) Where is the air pump fuse?
2) If the pump is dead, what are the chances that the combi-valve is dead also?

I will check under the hood once the temperature warms up a bit (been -20C for days). Just preparing myself for the coming assult on my wallet...

Thanks
 
#2 ·
The fuse is in the ECM box, if I remember right. 40 amp.

If the pump is dead, and it is full of water, it is BECAUSE the kombi valve went bad.

The water is condensation formed by hot exhaust backfeeding into the piping down to the pump.

Quickest diagnosis is to pull the hose off at the pump. If water comes out, and it smells exhausty, order a pump and a valve.
 
#3 · (Edited)
Finally got around to looking into this air pump problem a few weeks ago. Here is what happened so far:

- When I pulled off the flex hose from the air pump to the Combi-valve (to see of the pump was still pumping air), the hose broke in half. I thought may be the cracked hose was the problem and ordered a replacement.

- With the hose off, the pump was still operational as far as I could tell, pumping away after a cold start. The hose/pump was not wet and didn't smell like exhaust.

- Replaced hose and cleared the CEL. Days went by and the code did not return. Yay, I thought to myself, don't have to buy a $300 pump.

- A few weeks later (today), wife said that CEL is on and when I checked, it was P0411 again (SAI incorrect flow detected)

What happened here? Why did it work for weeks after the hose was replaced? Just a coincidence that some other piece of the system broke after the repair?

Oh, when I was replacing the output hose, I hooked up the Combi-valve side and left the pump side open and then started the engine. Through the open end of the hose I could feel pulses of air/exhaust. Is this normal?

One last thing, what sensor is used to determine that the air flow is incorrect?

EDIT
Took things apart again.
- Unhooked the vacuum hose to the Combi-valve, started up car, felt vacuum at the end of the hose (solenoid is OK?)
- Unhooked output hose of Air pump, hooked up a syringe+silicon hose to Combi-valve. Blew into air pump hose...valve closed. Pull syringe to create vacuum (hopefully enough to open combi-valve), blow into air pump hose...valve is still closed.

Assuming I had enough vacuum with the syringe, looks like a bad Combi-valve stuck closed. Is this a common failure?

Is the Combi-valve difficult to replace?
 
#4 ·
Bump

Is it common for the Kombi-valve to fail into the "closed" position? Ususally read about ones that leak and eventually kill the SAIP. I am not sure if I had enough vacuum to open it with a syringe. Then again, when I had the vacuum hose off and started the engine, the suction at the hose didn't feel like much.

Any other way to check it? Visual inspection after removing it from the engine?
 
#6 ·
Visual inspection after removing it from the engine?
i've posted this before, might as well again:

Week of May 1, 2001

Subject Number 1:

A4 1.8T Engine Code ATW

In the event you have an A4 1.8T with engine code ATW with the DTC of 16795 - Secondary Air Injection system, Incorrect flow Detected, a leaking Combination valve could be the problem. A leaking valve causes exhaust gas to enter the secondary air system. The water from exhaust condensation travels through the entire secondary air injection system and if the temperature drops below 0 degrees Celsius the water will freeze. In most cases the water causes the air pump to corrode. Inspecting the combination valve will reveal the problem. If the Intake side of the valve is black, exhaust has entered the secondary air injection system.
 
#8 ·
That was my first project this year..what I have learnt from this forum is:
Bad combi valve --> Bad SAIP.

Mine was throwing the same code coupled with the classic whistling noise (My neighbors thought I had an experimental car!)

I changed the combi valve, the SAIP and the connecting hoses (mine crumbled into pieces too - also had to spend a lot of time trying to get the bolts off the rubber mounts), cleared the codes and have been good ever since (last Sep)

Going thru my service papers I noticed that both the combi valve and the SAIP had been replaced once before at around 50 to 60K Miles.
 
#7 ·
Is the intake side the one coming from the engine, if so that side is clear, the side going to the air box is brown, and the entire pump is full of water.


If i were to use one of those SAIP plugs would i pass the smell test for smog once my cat warms up?

Would it still throw codes if i plug it?
 
#11 ·
Is the intake side the one coming from the engine, if so that side is clear, the side going to the air box is brown, and the entire pump is full of water.
the side going to the airbox. so if that has got crap in it, the combi valve is bad.


If i were to use one of those SAIP plugs would i pass the smell test for smog once my cat warms up? ?
no, your car has to pass all readiness codes.

Would it still throw codes if i plug it?
probably...readiness is based on O2 readings, so if the SAIP isnt injecting air on cold start->codes.
 
#12 ·
combi-valve replacement procedure?

I have a P0411 code on my '99 2.8L V6. The SAIP whines like a turbine. I'm sure it's louder than it should be, but I don't remember what it used to be like. So I'm sure it has to be replaced.

And I'd guess that at least one of the combi-valves is not working right. Is there a method for testing them without removing them? How can you tell whether they open and close when vacuum is applied and air is blown into the inlet tube? Is it audible? I'd rather not remove one if I know it's working correctly. And I'd rather not buy two if I only need one.

The combi-valves look like they're awkward to replace on the V6, right at the back, very close to the firewall. Any tips?

When you buy the replacements, are they complete with the curved sections that actually bolt to the cylinder heads, or just the upper portions to be bolted on to the original bases? And do they come with new seals, or do you need to order the seals.

From other threads in the forum, it looks like the SAIP is about $230, the combi-valves are about $130 apiece, and the two air pipes (from airbox to SAIP and from SAIP to combi-valves) are about $120. So I'm looking at $610 or more in parts. Does that sound about righht?

Thanks for any comments,

- Roger
 
#13 ·
well i just did some searching and you can get a uses SAIP pump on ebay for pretty cheap. I got it all with the combi pump and all hoses for 120 shipped.

And also i believe if you relace the valve really soon you may be able to save the pump. I think.
 
#15 ·
A really late follow-up, because I only just fixed the P0411 problem. And I'm kicking myself in the butt for not having found it earlier. A professional that had worked on the engine earlier had installed the check valve in the vacuum line backward, so there was no vacuum to the combi valves. I reinstalled it the correct way, and all is well.

Moral of the story: make sure there's vacuum in the line to the solenoid valve, and that on a cold start there's vacuum to the combi valve.

Long story for anyone interested. Fairly early in its life, the Passat (my wife's car) was hit in the front right corner, the shroud over the right-side cam belt was damaged, the belt broke, and several valves got bent. It was almost an insurance write-off, but they wanted it rebuilt. A while later, my wife reported hot oil fumes, so it went back to have the oil leak fixed. Still not right, and she eventually took it back again. A few months after that, I noticed the CEL was on; "yeah, it's been on for a while" came the response. The VW guy decoded it, said it's probably the solenoid valve, none in stock right now but easy to replace. We lived with it a while longer, I got a new solenoid valve, installed it, cleared the codes, but the CEL came back on. Note: I failed to check for vacuum, assuming the VW guy knew his stuff.

I eventually bought a pair of used combi-valves, and compared the noise they made as they opened when vacuum was applied using my hand-held vacuum pump with the ones on the car. Same noise. That's when I finally got smart and tested the vacuum line, and found the mis-installed check valve.

So don't be a dumb a$$ like me, be methodical, don't leap to the wrong conclusion.

- Roger
 
#23 ·
To combine two answers in one post, SAP flow is monitored by the ECU using the readings from the secondary O2 sensors. With these two codes, I'd suspect your passenger side post-cat O2 sensor is bad, since you have a direct code for it, and having no readings from that sensor can trigger the SAP code as well, since no signal from it at cold start means the ECU is essentially seeing no airflow with the pump running.
 
#21 ·
Update -

I thought I would post an update. I ended up taking my car to a shop that looked at my SAI system issue. They found that the SAI relay that is located under the ECU was bad. They replaced it and cleared the code. Only time will tell if that was the only issue, but looks good so far. They said the relay passed a preliminary test, but upon further investigation one of the terminals was bad.
 
#24 ·
Hopefully they didn't hose you for labor as it takes less than 10 minutes to reach in there and swap out if you can maneuver through the side-panel where fuses are.
The SAIP relay isn't under the dash with the rest of the relays. It's in the plastic ECM box in the engine bay, tucked under the drivers side of the windshield. The SAIP fuse is in there too.
 
#27 ·
theMatrix

I am trying to locate the check valve and the solenoid valve(mentioned below) on my 2000 Passat. Can anybody point to me where I can find it...
(A 2001.5 1.8T AWM engine is pictured.)
N112 is the SAIP solenoid valve, mounted under the intake manifold where the text is.
N249 is the solenoid valve for the DV, mounted on the same bracket as N112.

There are five check valves; four are near N112--you can see one in the photo, over top of the suction jet pump. The fifth check valve is over behind the air box, also visible in the photo. The coolant tank is lifted up for easy access (only the electrical connector is disconnected).

 
#31 ·
A fuse blows when amp flow through the fuse exceeds the fuses rating.

That 40A fuse protects the SAIPump motor and circuit. Something in that circuit is allowing more than 40A to flow. Does your SAIPump still spin up and sound normal before the fuse blows? Or does the fuse blow instantly when the system cycles on? Do a resistance check from the + terminal of the motor to ground. If you see no resistance, the motor is burnt and grounding out. Do a resistance check from the + wire feeding the motor to ground. If you see no resistance, the wire is grounding out somewhere along its path.
 
#32 ·
Steve- I will check your suggestions on my car. After thinking about it for a while, I haven't heard the pump lately, and it was quite loud the last time I heard it. Before asking my question, I pulled both the relay and fuse (fuse is visibly bad), but the external tongs on the relay appear to be in good shape... I'm thinking I'll get another one JIC. Fuses are cheap, I don't mind blowing them based on the cost of replacement, however, I do know that something in the protected circuit caused said fuse to blow. I asked because I was curious if there were any common reasons (on our vehicles) that this fuse blows, other than shorts. I thank you Steve for pointing me in that direction. When I get home tonight, I'll :wrench: away and report back.

p.s. After the response last night, I started to state that I understood how fuses blow... but then though better of it as I'm sure there would be those who thought I might actually believe that what I may or may not do at night would affect a fuse :thumbup:
 
#33 ·
I re-read your other post and think I missed part of your question.

An electric motor draws a lot of amps trying to spin up from a complete stop. Once it's up to speed, amp flow drops off and then depends on how much load the motor is under. A free spinning motor draws very little but if you apply a load, it will draw more amps.

The protection on this circuit is probably sized to withstand a momentary high startup draw then hold a lower sustained draw.

If your SAIPump motor is seized or if the bushings are worn and not allowing it to spin freely (mechanical failure), it will draw more amps than it normally would. This could blow the fuse even though the circuit is fine electrically. This is why I asked how the SAIPump sounded and how quickly the fuse blows.
 
#34 · (Edited)
Thanks Steve,

Unfortunately, I was unable to really work on the car since my last post. I had a weekend full of inexpected interuptions (like driving 2 hours each way to pick up my young brother in law and his "new" car that broke down 15 miles after he handed over cash at a gas station... got that phone call at 9 pm friday night, finally in bed at 4:30am and back up at 6am to go to work :icon_eek: I did put a new fuse and relay in, but I didn't hear the SAIP spool up when I started it (first time starting it in over 24 hours). The fuse didn't blow though. I think I'm just going to order a new Combi valve and SAIP. The valves I've seen are all around the same price, and one of the local dealerships has both the Combi and the pump in stock.

does anyone have any experience with aftermarket pumps like the one on ECS? Is it worth saving $400 or should I stick with the OEM?

http://www.ecstuning.com/Volkswagen-Passat_B5-FWD-1.8T/Search/Air_Injection/ES1876813/

http://www.ecstuning.com/Volkswagen-Passat_B5-FWD-1.8T/Search/Air_Injection/ES2532875/
 
#35 ·
Try these guys. Better pricing and shipping charges. I use them all the time. I do know that Uro parts is on the low end of sht scale from other parts purchases I have made over the years.

GermanAutoParts.com
 
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