Hey guys I have an "EGR flow insufficient" code and I've replaced my egr valve, DPFE sensor, the solenoid and the purge cylinder. I've taken all the lines off and cleaned them out. Each time I replace a part I reset the code and test drive it and I make it further and further each time but it still eventually pops on. If anyone else has had this issue and has any ideas I would really appreciate the help.

 

Welcome to the forum

It is a good idea to look up ALL the codes for a system before replacing parts
"Most" of the EGR codes here:
P0400 - Exhaust Gas Recirculation Flow Malfunction
P0401 - Exhaust Gas Recirculation Flow Insufficient Detected
P0402 - Exhaust Gas Recirculation Flow Excessive Detected
P0403 - Exhaust Gas Recirculation Circuit Malfunction
P0404 - Exhaust Gas Recirculation Circuit Range/Performance
P0405 - Exhaust Gas Recirculation Sensor A Circuit Low
P0406 - Exhaust Gas Recirculation Sensor A Circuit High
P0407 - Exhaust Gas Recirculation Sensor B Circuit Low
P0408 - Exhaust Gas Recirculation Sensor B Circuit High

I assume you got 401?

Many of the codes have to do with wiring, and the codes the Computer did NOT use are as important as the code it "chose" to use

EGR system has 4 parts
1. EGR valve, this is opened using vacuum from EGR modulator/solenoid

2. EGR modulator/solenoid, is connected by vacuum hoses to intake manifold and EGR valve, it also has 2 wires, one will have 12volts when key is on, other wire goes to computer, computer pulses Ground on this wire to apply vacuum(open solenoid valve) to EGR valve, by varying the ground(pulsing) the solenoid can be opened a little or alot which opens EGR valve a little or alot.

3. DPFE sensor, this has 2 Exhaust hoses connected to EGR tube or exhaust manifold, the hose closer to the EGR Valve will have lower pressure if EGR valve opens, the more the pressure difference between the 2 hoses the more the EGR Valve is open, so higher flow, DPFE = differential pressure feedback, or Delta pressure feedback
DPFE uses 3 wires to read pressure difference for computer
DPFE sensor will usually need to be changed every 80-100k miles, they get water inside from exhaust gases, all exhaust has water in it, which is why tail pipes drip water and exhaust systems rust from the inside out.

4. Computer, it interprets sensor data, it has stored parameters of sensor ranges, and circuit connections, wiring part.

P0401 "EGR flow insufficient"
So what that means is that the computer is Grounding EGR Solenoid to open EGR Valve but the DPFE sensor is not showing a drop in pressure high enough for the Ground pulse.

So could be Vacuum line from intake to EGR solenoid is clogged, or leaking
Vacuum hose to EGR Valve is clogged or leaking
DPFE sensor hoses are clogged or leaking

Wiring may not be grounding EGR solenoid, at computer end or solenoid end

EGR solenoid may not be getting 12volts key on, although that should set another code, circuit A or B low

 

Thank you! And yes I am getting a P401. The one thing I haven't checked would be the ground wire, this is the first time I have heard of that. I think it also might be a vacuum line because I discovered part of my vacuum reservoir was melted. I just ordered one this morning and should receive it this week. Thanks for all the advice and clarity.

 

EGR system often used vacuum reservoir, its mainly for cab vent selection, depends on the year of the vehicle.

So yes could definitely be vacuum reservoir issue.
EGR system needs a stable vacuum(like power brakes) so EGR Valve is stable not drifting open and closed as vacuum in intake goes up and down with throttle position