Hi guys. New here and looking for advice/help. I have the code (P0405. Exhaust gas. Recirculation sensor a. Circuit low) I did some tests on my dpfe sensor going by this thread https://www.ford-trucks.com/forums/34...fe-sensor.html and I get 1.03 volts on the top wire with KOEO and 5 volts on the bottom wire...when i applied suction with a hose attached to the forward most hole and it changed and went up to about 2.08 no matter how hard i sucked on the hose....two things i noticed are that the suction did not hold my tongue(with or without the back hose connected.) and the back post for the hose seems half the length of the forward one and the hose came off extremely easy...the ID of the hose looks the same as the other one....also, i sprayed for vacuum leaks and found none and I took the top hose off of my egr and applied vacuum and the the engine idle lowered some but not to the point of dieing. So....is my dpfe bad? and should have the egr totally made the truck stall?
Mind if I tell you the 405 code tells you the 'circuit' is high.
That's an electrical fault the PCM has detected.
This means the system operation can't be tested for performance because the sensor does not work to report the test results.
Testing the sensor won't tell you much bad or good.
If the feed voltage is good, it's either the connector or the sensor is faulty or the signal lead back to the PCM is in fault.
Once you replace it and clear the code, it may take two drive cycles to complete the PCM test, to see if the fault is cleared.
Normally the short hoses are two different ID..
The sensor needs the 5 volts to power the DPFE electronics.
The electronics are set up to measure pressure difference between the intake ports and report that level signal back to the PCM where it's compared to a table.
The code failure is the sensor not powering properly so the ability to read pressure difference can't be made.
The PCM monitors the DPFE circuit for current flow to test the sensor and harness.
Beyond this the PCM goes through a series of EGR system performance test requests separately, to determine the system operation.
So both bases are covered.
I'm bringing you the fine points of operation so you better see what it's all about.
It likely is the DPFE. Get one or borrow one to try.
Testing it is hardly ever is very accurate.
It's a lot like telling time from one clock or two clocks. One clock you have one answer right or wrong. With two clocks saying a different time, you still don't know which one is correct if either one is or not.
I replaced the DPFE Sensor on my 2001 4.6 back in 2011. It was $50 and some change from the dealer. Be very careful with the silicon hoses, as I couldn't find them anywhere, other than on a large spools. I cleaned the tubes going down to the exhaust pipe with springs and wire, followed by compressed air.