Inexpensive fix for code P0491 secondary air injection diverter valve problem!

Hi mech2; I purchased the check valve at Auto Zone. Go to their web site and in the replacement parts search tab type in 355050 which should bring up the Dorman / air pump check valve part #355050. Cost is $9.99. After you get the check valve, go to your local hardware store and purchase a galvanized 3/4" hose to 3/4" NPT threaded pipe adapter or fitting to screw into the check valve to have a hose fitting at both ends of the check valve. The hose fitting that is original to the valve points toward the air pump (front of vehicle), and the galvanized fitting points toward the firewall or exhaust (blow into the check valve to make sure the air is going to flow from the air pump to the exhaust). You would want some thread sealer for the threaded part. After installation, plug up the vacuum line that went to the old check valve, Zip tie it to the side, and suspend the new check valve using the old valve bracket and piece of strong wire so it won't rub on the transmission. Clear the code and then do a drive cycle to reset all the ECM monitors which is in the owners manual under battery replacement. This fix has been working great for close to two years, and the engine control module is completely happy with it. Let me know if you have any other questions. lightsaber I called Ace hardware for the galvanized fitting, and they say it is Ace part# 41759 and cost is $2.49. This fitting is normally uses for the black plastic water line used for outdoor water wells, etc. The type of black plastic line that is rolled and can be unrolled and run across the ground surface. The automotive thread sealant should be oxygen sensor safe such as Permatex pipe thread compound, etc. You will also need two stainless steel hose clamps for the connections at each end of the check valve.

Hi leegee2; This fix should work fine for your 2008 Fusion 2.3l also! Good Luck.

Rubber hose that leads to exhaust. Same hose that connected to the original part.

The big hose connects to inlet ,the other side had the nipple on it that connected to diverted valve , barbed end is to big to connect to that ? Sorry I'm just learning ,I have big hose connected but other side doesn't have anything to connect to it ,THANKS FOR YOUR HELP & PATIENCE! Maybe my setup is different, mine is 08 fusion

You may be trying to connect the new valve at the airbox?? That is wrong. First I assume you are replacing your OEM diverter valve. Two bolts must be removed that attach the OEM diverter valve to a bracket. This bracket is near the driver's side end of the valve cover at the top of the engine. It is a round valve with a small vacuum hose attached at the top rear. Remove the OEM diverter valve, and set it aside. The new parts (Autozone check valve plus Ace h/w barbed adaptor) connect to the two hoses that were connected to the OEM diverter valve. This all assumes your OEM diverter valve was bad and requires replacement. There is a thread elsewhere that describes how to determine if you OEM diverter valve is bad. In my case I bought a vacuum pump for $20 from Harbor Freight to attempt to make the OEM diverter valve open, then attached a heater hose to the input of the diverter valve and attempted to blow air through. My OEM diverter valve was stuck closed, so it needed to be replaced.

The replacement Autozone valve does not require a vacuum line connection, so the vacuum line that connected to the OEM valve should be plugged with a screw if you replace the OEM valve with the Autozone valve.

My "bench test" was blowing through the Dorman valve with my mouth. I was also surprised how much air resistance that valve presents and I also thought that's probably the reason for the OEM vacuum-actuated version. But anyway I am using the Dorman valve for about 6 months now with no problems or OBDII codes.

I successfully passed NYS inspection and it's been about a week with no CEL. Just passing along another success story. Thanks so much for the info, saved me all that money on the oem diverter valve!!

It sounds like you found a very good option. I don't think "safety" is a concern with the static one-way valve. The Dorman static one-way valve used in this thread does have a pretty high resistance to airflow, apparently part of the one-way design that can stand up to heat, etc. That said, that static one-way valve is still working well for me after 7 months.

Yeah the point of this fix is purely budget. The Dorman Check Valve was $10 with free shipping from Autozone, and I had the 1/2 X 1/2" barbed fitting, but they are a few bucks at best. So your talking $15 bucks tops, Vs your $135. If you truly study and understand the system, you'll know any check valve will works as long as it can withstand the exhaust temperature. I'm not sure why the original is vacuum controlled, but I suspect it's so there is less pressure drop across it, as I mentioned above. However, even the original has some restriction and the Dorman still allows enough air flow to satisfy the 02 sensors. Also, I understand OEM is thought to be the best, but remember its that OEM setup that failed thus putting you in this situation. So either way will work, but keep in mind, you may need the pump assy too. Usually the CV fails and water gets into the pump. And lastly, you can put some drain holes on the pump rubber boot housing if any water does get in there.

Yes now that you say it I remember the same thing. I just used a hose clamp. You could get a 3/4 barb I suppose but I was just following previous posts for the size. Its pretty amazing how many people have these systems dropping out. A lot of aftermarket money for Ford (unless you are like us doing it this way!!). I tested my pump too and it was shot. And actually by doing the fix this way, you eliminate the vacuum solenoid as a future failing point.

I think I watched that same video plus found an electrical schematic for this circuit one of these links. Yes, backprobing with a grounded wire at the correct wire (purple stripe) on the correct connector (near the solenoid) you can cause your secondary air pump to run so you can find out if the pump is good before proceeding with this fix. In my case the pump was still working (lucky) but had water in it and about 1 cup of water blew out the end of the disconnected hose when I tested the pump. I also used that method with the new Dorman valve partially installed to see how much air was coming out the output side before finishing the installation.