I’ve been having a constant P0410 code on my DIC for a couple weeks now on my 2000 corvette.

Before replacing anything, I disconnected the rubber hose next to the alternator and tested for constant cold air flowing during a cold start. There is constant air coming from the secondary air pump on cold starts.

With the engine running and With the previously mentioned hose disconnected, I felt for exhaust gases coming from both air check valves, and I can hear gurgling noises and feel mild pulses of warm air indicating one or both air check valves are not functioning properly and have became “either-way-valves”…. Is this the correct way to diagnose for failed air check valves??

When I took out the old air check valves, I tested each with the blow test and both valves allowed a little bit of my breathe past the rubber diagram, so I assumed the valves are bad.

I replaced driver-side and passenger-side air check valves today. Before I installed the new valves, I blow-tested the new valves to ENSURE the one-way function is working properly, both valves PASSED the blow test. BUT after I installed the valves and but the intake manifold back, I disconnected the same hose and now i still feel mild pulses or warm air AND i hear gargling noises coming from the check valves hose.

Can someone explain how this is possible???

I cleared the P0410 code and will continue to monitor if the code will return, indicating there is still a problem.

The only reason I even care to fix this is because I live in california where my car needs to be smogged.

Thank you all

 

A P0410 is not a “check valve” issue but a “general” one so first you need to know what sets that DTC…the O2 sensor voltage does not decrease below 222 mv’s during the test so there are many components that could have failed to set this DTC…failed AIR solenoid, relay, pump, shut off valve, AIR relay, no vacuum to the shutoff valve from the solenoid…without a factory level or equivalent scan tool you will find it difficult to diagnose this and we don’t know your electrical “skills” and the tooling you possess…best thing for you would be to find an auto electric shop in your area and let them repair this….there are 2 separate DTC’s for the check valves BTW…flow chart below if you think you can handle this but unfortunately we would find it almost impossible to guide you through each step…with the scan tool you can basically activate the whole system and you can watch those O2 voltages decrease…you can also energize the solenoid and pump and if the car is running you can see if you do have vacuum at the shutoff valve.

 

My guess is there is not adequate exhaust pressure at idle to complete close the valve. Remove the tube side (from A.I.R. pump) from the check valve, and connect a vacuum pump. Pump up to 10 in Hg, if the vacuum drops off within 5 seconds...valve is bad.

P0410 is very easy to diagnose, and while it helps to have a scan tool, you certainly do not need one to isolate the issue. Feel free to PM me and I'll walk you through it.

 

Exhaust pressure to “close” the valve ??…huh ??…which valve are you talking about ??…if the PCM doesn’t see the O2 drop below 222mv’s that may be either weak AIR pump flow or a bad shutoff valve not opening completely due to low vacuum.

 

I specifically responded to the OP's question (quoted his response) about the check valves he replaced, and what he observed after replacing the check valves.

Perhaps this will clear things up for you.












..

 

No, that’s ok !!…I fully understand how the system operates !!

 

 

It might be important to mention that I disconnected the hose next to the alternator and I can feel cold air coming from the hose attached to the air pump during cold starts. HOWEVER, when this hose is detached, I can also hear the air coming from this hose characterized by a humming sound.

Because I hear this humming sound, I can audibly hear when the SAI pump is running when I’m inside the cabin of the car.

It’s worth noting the pump sometimes comes on randomly when driving and also comes up sometimes when i start the engine and the engine is already warm.

 

I’ve never heard this pump “hum” so you may have a bad pump…I could never hear it running when I was in the car….unfortunately we can’t diagnose this for you over the internet…I’d seek out a specialist to see exactly what’s happening.

 

It’s not the pump making the humming noise. It’s the air coming out from the hose from the air pump solenoid. If I cover the hose with the thumb, the noise goes away, so I know it’s the air making the humming noise.

 

Air by itself doesn’t hum so it has to be a result of the pump running…don’t know what else to tell you…where are you located ??…I may know of a good diagnostic shop in your area.

 

San Diego CA. Thank you for the tips and knowledge! I’ve been scratching my head on this one for weeks now

 

Sorry but I don’t know of any shops in your area.

 

After more thorough half splitting and troubleshooting, I have found the main issue.

The Vacuum line connected to the AIR shut off valve is not providing vacuum.. this is causing the air shut off valve to not open and allow air flow to the driver side and passenger side air check valves, therefore the O2 sensors aren’t picking up the increased O2 values, thus causing my P0410 code.

I connected a separate hose to the vacuum supply on the air shut off valve and applied vacuum manually. This resulted in the air shut off valve opening, allowing air to flow to the check valves and eventually into the exhaust manifold.

I need to now figure out why there is no vacuum being applied at the air shut off valve.

Does this necessarily indicate a vacuum LEAK or maybe the air vacuum solenoid is not actuating.

 

The vacuum that goes to the shut off valve comes from the solenoid valve…you will have to check that solenoid…with a factory level scan tool you can actuate the solenoid…it is above the PCM…you need to see if the vacuum line is broken or the solenoid is inop !!…the solenoid power is the pink wire and energized with the ignition 1 relay energized…the control wire is ground side switched so the PCM is supplying the ground…with that scan tool you can easily check the solenoid…if you can apply vacuum to the vacuum line you can determine if it leaks…my friend Matt did a video on the diagnosis…he found a bad solenoid !!

 

Thank you for the advice. I’ll use a scan tool to activate the air solenoid to check for vacuum.. HOWEVER… I believe i have found the source of my problems.

After doing research, I learned there is a vacuum line beginning at the MAP sensor behind the intake manifold and that line runs down to behind the PCM and supplies vacuum (through a series of check valves) to the vacuum reservoir, HVAC, and the air pump solenoid.

I pried open the passenger fender to gain access to some of these lines.

1. I then disconnected the vacuum line that runs to the back of the intake and attached my vacuum gauge.
2. Then I turned on the car to check for proper vacuum, the source being behind the intake manifold.
3. I have no vacuum coming from this source
4. So now my solutions will be to attempt to remove the intake manifold (again) and run a NEW vacuum line down and hope all the valves are good and hope to get good vacuum to the air solenoid and then to the air shut off valve.

IN ADDITION:
It makes sense now why the driver side of my cabin blows hot air and the AC doesn’t work.

Pictures:

Vacuum gauge attached to vacuum supply hose coming from intake manifold

Closer look to verify that i hooked up my vacuum gauge to the correct line. Yes i know I broke the line disconnecting it, but I was going to replace it anyways. These crappy old Nylon vacuum lines suck.

 

I also wanted to ask:
Because there is a vacuum leak from the vacuum reservoir supply line, will this cause unmetered air to enter the intake manifold and create backfires and rough idling?

Is the an engines entire vacuum system all connected in one closed loop?

Will a vacuum leak ANYWHERE cause misfiring, rough idle, backfires, or even messing with anything else that requires vacuum to operate? For example, will this vacuum leak effect the vacuum to my master brake booster, since that operates on vacuum as well?

Thanks.

I never learned the importance or even dealt with vacuum issues in a car until i purchased my c5. Learning a lot!!

 

If you would have told us this INITIALLY this could have been diagnosed in 2 seconds !!

 

You have a separate vacuum source for your brake booster and yes a vacuum leak will elevate your fuel trims at idle when manifold vacuum is at its highest…as the throttle plate is opened there is less pressure differential between the intake manifold and outside air pressure…an excellent video below from Matt…it is a 2 part video.