Help with P1409/DPFE/EGR

[Dekeman]

Hello all,

I have been trying to test my EGR system using a new multimeter. In reading the code the engine is giving, it is a P1409, which according to AutoZone, says:
EGR vacuum regulator circuit fault
ECM commands EGR vacuum regulator on-
System voltage too high or low
Probable cause:
1- Failed EGR vacuum regulator
2- Open or shorted circuit condition

AllDataDIY says:
P1409- EGR Vacuum regulator solenoid circuit malfunction
This test checks the electrical function of the EGRVR solenoid. The test fails when the EGRVR circuit voltage is either too high or too low when compared to the expected voltage range. The EGR system must be enabled for the test to be completed.
Possible causes:
EGRVR circuit open, VPWR open to EGRVR solenoid, EGRVR circuit short to VPWR or GND, damaged EGRVR solenoid, damaged PCM.
The EGR vacuum regulator solenoid resistance is from 26 to 40 ohms.

There are many mentions of a short in the system, and as I have the old-style silver aluminum DPFE box which is a known problem, I have tried this first as the most likely cause. The EGR is simply a vacuum-activated valve and does not receive power, but the DPFE is a powered item, thus making this the likely cause of a short circuit in the system.

I am trying to test each lead, but I am not sure if my method is correct. I am testing for DC voltage on an autoranging multimeter, and unplugging the DPFE harness, then connecting the positive test lead to the harness contact and the negative lead to the corresponding pin within the DPFE. The meter is still hunting for a reading and does not stabilize. I know the meter works properly as I have tested it elsewhere and gotten the expected results. Either my method is incorrect or this DPFE is dead as a doornail. Can anyone help?

[wiswind]

The EGR vaccum control solenoid is mounted on the back side of the upper intake manifold.....toward the driver's side of the vehicle.
The vaccum line that goes into the top of the EGR valve goes into the EGR vaccum control solenoid.
There is another vaccum solenoid mounted on the firewall very close to this......but that is the vapor recovery solenoid.

The EGR vaccum solenoid has 2 vaccum lines connected to it.....1 from the vaccum source, which has a number of other things connected to the same source.
The other is the vaccum line from the EGR valve.
There is an electrical connection also, which goes to the PCM (computer).
The actual electrical signal to the EGR vaccum control solenoid will be a A/C waveform as the signal varies to control vaccum to the EGR valve......to open/close it to obtain the desired flow.
The EGR valve is not fully open....but only enough to obtain the correct flow, as measured by the DPFE.

If you look at the vapor canister solenoid nearby on the firewall, you may notice a small "hat" on it.
That "hat" contains a felt/foam filter.
I have read a post or so about that filter getting clogged on a vaccum control solenoid and causing it to not work properly.

Because of the location, on the back side of the upper intake manifold, it is not easy to get a picture of anything back there.
I wish I had taken a better picture when I had the upper intake off....but this is the best that I have.
This picture shows the upper intake manifold as viewed from the bottom, intended to show the upper intake manifold gaskets.
In this picture, you can see 2 vaccum control solenoids......the one closest to the throttle body is the EGR vaccum control solenoid, the other one.....farthest to the left is the IMRC vaccum control solenoid.
The largest vaccum connection that you see, closest to the throttle body location, is where the fat vaccum line from the power brake booster connects.

[Dekeman]

Thanks for the great pic, Wiswind. So the vacuum control solenoids are the round things on the bottom of the picture, thus putting them on the left side of the engine or the rear of the engine compartment near the firewall? Also, is it possible that the tube from the solenoid to the valve is bad? It pulled off of the valve too easily.

[wiswind]

Those are them.
There is often a very slight vaccum in the hose to the EGR valve at idle......but not enough to open the valve.
You could check the hose to see if it can deliver a vaccum from one end to the other.
Also....there should be enough length that you can trim a quarter inch off the end (check before cutting) and see if that helps it seat a bit tighter on the EGR valve.

[Dekeman]

It sounds like the most likely route is to replace the EGR vac regulator. Now that I have a better idea of what I'm dealing with, it doesn't seem so impossible. Is that sounding likely to you too?

[Dekeman]

Bump

[wiswind]

I would only be guessing.
It is possible, the only way to know is to replace it.
Since the code is directly indicating that it is not happy with the electrical picture that the PCM has of this solenoid....not the condition of the vaccum, but the electrical continuity of it.....it would seem likely that the solenoid is defective.
Of course, if you get back there and unplug it......and find something wrong with the wires goint to the solenoid.....or that it is unplugged (unlikely), then that could also be the cause.
It is more likely the solenoid, or the wires between the solenoid and the PCM than the PCM causing the problem.
Also, the PCM is more expensive.....on top of it being unlikely to the be the PCM.

[Dekeman]

I'm gonna get on Rock Auto and get a solenoid then. Thank you Wiswind!

[Dekeman]

Replaced the EGRVR and all seems to be well. Have been through two drive cycles after resetting the PCM, so we'll see. Went to the dealer for an OEM part.