Sounds like a Cicada
#1
Sounds like a Cicada
I have been trying to fix a P0401 Code on my 98 2.5 in sig. What I believe may be a symptom to the code is an intermittent noise that sounds like a Cicada, the noisy flying bug of summer. It has the same volume when cruising, not accelerating or decelerating. I'm thinking it is vacuum related. Has anyone had this and fixed it?
Thank you
JIm
Thank you
JIm
#2
P0401 Exhaust Gas Recirculation Flow Insufficient Detected
This is generally a DPFE sensor issue
EGR system is pretty simple
There is an EGR Valve on the intake manifold that is connected, by a metal tube, to the exhaust manifold, this valve is opened by applying Vacuum
There is an EGR Vacuum solenoid valve that applies vacuum to the EGR valve, this solenoid is controlled by the computer(PCM)
There is a DPFE(differential pressure feedback) sensor connect with two rubber hoses to the Metal tube between exhaust manifold and EGR valve
When the computer opens the EGR Valve, applies vacuum, it monitors the DPFE difference between the two hoses, i.e. the hose closer to EGR valve will have a bigger drop in pressure than the one farther away, this tells computer how much exhaust is traveling up the metal tube and into the intake.
P0401 means the "reported" pressure drop is not high enough, so Insufficient Flow
So first test that the vacuum lines on the EGR Valve and the EGR solenoid are OK, no cracks or breaks
Then check the TWO exhaust hoses from the metal EGR pipe to DPFE sensor are OK, no cracks or breaks, also make sure there is no water in these hoses, yes water
If all are OK then replace DPFE sensor on speculation, because these do wear out from moisture intrusion
If that doesn't get rid of the code then you will have to clean EGR valve and tube as they are clogged up with carbon build up, can be a big job
This is generally a DPFE sensor issue
EGR system is pretty simple
There is an EGR Valve on the intake manifold that is connected, by a metal tube, to the exhaust manifold, this valve is opened by applying Vacuum
There is an EGR Vacuum solenoid valve that applies vacuum to the EGR valve, this solenoid is controlled by the computer(PCM)
There is a DPFE(differential pressure feedback) sensor connect with two rubber hoses to the Metal tube between exhaust manifold and EGR valve
When the computer opens the EGR Valve, applies vacuum, it monitors the DPFE difference between the two hoses, i.e. the hose closer to EGR valve will have a bigger drop in pressure than the one farther away, this tells computer how much exhaust is traveling up the metal tube and into the intake.
P0401 means the "reported" pressure drop is not high enough, so Insufficient Flow
So first test that the vacuum lines on the EGR Valve and the EGR solenoid are OK, no cracks or breaks
Then check the TWO exhaust hoses from the metal EGR pipe to DPFE sensor are OK, no cracks or breaks, also make sure there is no water in these hoses, yes water
If all are OK then replace DPFE sensor on speculation, because these do wear out from moisture intrusion
If that doesn't get rid of the code then you will have to clean EGR valve and tube as they are clogged up with carbon build up, can be a big job
#3
Thank you for your response.
I have replaced the DPFE sensor and the lines to it. as it showed bad with the VOM testing. I'll verify the lines are oriented correctly. I'll inspect the lines you mentioned. I am thinking a clogged line in the EGR and intake manifold, so removal and cleaning may be in order.
Thank you again
Jim
I have replaced the DPFE sensor and the lines to it. as it showed bad with the VOM testing. I'll verify the lines are oriented correctly. I'll inspect the lines you mentioned. I am thinking a clogged line in the EGR and intake manifold, so removal and cleaning may be in order.
Thank you again
Jim
#4
#5
After further checking, I ran a line from the line that goes to the EGR valve to a vacuum gauge mounted on my wiper blade and drove the truck. The gauge responded as expected, going to > 5" Hg when accelerating and dropping to 0" Hg immediately when off the accelerator.
I attached my hand vac to the EGR and upon applying and releasing vacuum, I could hear the pintle operate, but the vacuum would not hold. I believe I have a torn diaphragm on the EGR. I'm thinking that under higher vacuum conditions the tear is allowing the diaphragm to vibrate causing the noise. Regardless I'm going to replace the EGR and when open check the intake port for carbon build-up
On this 2.5 what works best to get the nut off the EGR Valve? It looks like it is 1 1/16". A crow's foot? A pipe wrench? I already started soaking it in PB Blaster
Thanks
Jim
I attached my hand vac to the EGR and upon applying and releasing vacuum, I could hear the pintle operate, but the vacuum would not hold. I believe I have a torn diaphragm on the EGR. I'm thinking that under higher vacuum conditions the tear is allowing the diaphragm to vibrate causing the noise. Regardless I'm going to replace the EGR and when open check the intake port for carbon build-up
On this 2.5 what works best to get the nut off the EGR Valve? It looks like it is 1 1/16". A crow's foot? A pipe wrench? I already started soaking it in PB Blaster
Thanks
Jim
#6
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