Cynic09GT

Sanity check, please.

Have been running in circles trying to diagnose the cause of a P0411 code. Ironically, I got this code after swapping out all 3 of the vacuum solenoids on the intake manifold, due to them all being original and also due to a P0410 code.

Hate that I have to do this to pass CA smog test, but it is what it is.

It is pretty clear that the cause of the new code is not the pump, but rather the secondary air valve failing to open. The air pump flows air as commanded on a cold start, but due to something wrong with the new solenoid there isn't enough vacuum present to open the valve.

This is the weird behavior I am seeing after installing a vacuum gauge to observe inHg present in the vacuum chamber on a cold start. The gauge was installed inline between the check valve and chamber.

Cold Start Vehicle
Air Pump Operates
Secondary Air Solenoid Opens
Vacuum Builds in Chamber, SLOWLY to ~ 5inHg, <<< This seems abnormal. Shouldn't full idle vacuum be present?
Two Minute Warm Up Period Ends
ECU Commands Air Pump to Stop & Secondary Air Solenoid to Close
Vacuum in Chamber Immediately Snaps to Idle Level (16-17 inHg)

Now compare this to observed conditions on a hot start:

Hot Start Vehicle
No Air Pump Operation
Secondary Air Solenoid Stays Closed
Vacuum in Chamber Snaps to Idle Level (16-17 inHg)

So it seems like something about the ECU command to open the secondary air solenoid, which should pull a 16-17 inHg vacuum on the air valve, is instead allowing atmosphere into the system.

I know it's not the hose between the air valve and the solenoid, because I checked the original, and tried a second hose to be certain. I have also followed diagnostic procedures in the FSM for valve operation, chamber leaks, etc.

What I did not do was bench test these solenoids before installing them. What are the odds that a new Mazda vacuum solenoid would fail internally, and prevent vacuum loss from the chamber (port A) while at rest but vent it through the filter cap (port C) when battery voltage is supplied?

Curious if anyone else has come across this.

toplessFC3Sman

I haven't encountered this issue, but it sounds like there is a leak in the the secondary air valve actuator or line leading to it, allowing air to bleed into the vacuum chamber and prevent it from reaching the idle vacuum level. Have you tried using a vacuum pump to check actuation of the secondary air valve actuator? I'd start with that, and see if you can get it to move and whether it leaks back up to atmospheric quickly. Check out the vacuum line running to it too.

UnknownJinX

I mean, new parts can fail. Not commonly, but sounds like you have narrowed down your options through diagnostics already.

Cynic09GT

An update: Disassembly and bench test confirmed that yes, the new Mazda OEM solenoid was defective, in exactly the way described above.

Page 1096 of the FSM references how the three ports of the solenoid should flow air under rest and +12V operation.

In a powered state Ports A and B should have flow, and C should be disconnected from both. This wasn't the case for me. On a powered state Port A and C would allow air to pass between them (should never happen), creating a vacuum leak.

If replacing your solenoids, bench test them first!