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Well am about 14 days out from my emissions test and am trying to put this issue to rest.
Am now left with P0402 and P1410, both code deal with the EGR. I have tested the solenoid that connects to the EGR, by applying a vacuum, which hold and gets released when I applied 12 V to the terminals.
The same with the EGR, It holds vacuum and release when 12V is applied to the middle & right terminal. So I am running against the clock here and I took it to one our local toyota dealers for diagnosis and they quotes me .... Wait for it..... $ 1300. they attached 2 pictures, one was the EGR and the other which i never paid too much attention was the "Valve Vacuum Control" pictured below. How does this work and how can i test it.
this time around, I also applied vacuum to the EGR, revved the engine and it held it the vacuum (granted the engine was not really hot).
Googled the parts number on this purplish part and its called the "Valve Vacuum Control"
they attached 2 pictures, one was the EGR and the other which i never paid too much attention was the "Valve Vacuum Control" pictured below. How does this work and how can i test it.
That one is a bit of a mystery for me. To simplify it, in the olden days, there was this thing called Vacuum Modulator, which used Exhaust to modulate when and by how much to open the EGR valve, below is a good video about it.
The thing is that said Valve Vacuum Control is supposed to serve the same function, but it doesn't have Exhaust coming to it, all it is a Membrane with a Spring, if there is too much vacuum, the membrane blocks the middle port, not allowing the Vacuum to pass from the intake to a VSV. The issue is that this was the only time they used this specific setup, even Camry with 1MZ engine had a more or less conventional Modulator, so I only have faint guesses as for how it modulates the flow and why it couldn't be done electronically.
A way to check it is to create vacuum in the Port S (in the Middle), while blocking Port Z (towards the Edge), they should be marked on the housing as well, if it doesn't leak, it should be good, it's really that simple. There is also a Filter in the Black part of the unit, which connects the Other side of the Membrane to the Atmosphere, you should be able to unscrew the lid and take a look at the filter, if it is clogged, it may prevent the Membrane from functioning, though it should be easy to clean.
With all that, I am still under the impression that, while the system is functional, all membranes intact and all VSVs move, the Main EGR valve itself may be clogged and either not opening, or the line that it does open is plugged. If you have never taken the EGR valve and that discolored pipe off and looked inside of the Manifold, it is a perfect time to do so, as again, it requires regular maintenance.
04-06-24, 10:28 AM
