EGR flow issues- where do i go from here?

[afbryant]

For the last couple of months, I have been having the bucking/surging in low gears. Been getting codes P0402, P139A and P139C. I have already tried two new DPFE sensors. After installing the sensor, I will clear the codes and they are back after a couple drive cycles. I have been only getting P139C recently. I know the basics of how to use an OBD scanner but I just got a tablet style diagnostic scanner and I am just learning the language , so bear with me
I have been checking out Live Data and it is showing:
"Desired Position of Exhaust Gas Recirculation (EGR) Valve"---0.00% -All the time, This value never fluctuates, it is always 0
"Position Sensor A Of Exhaust Gas Recirculation (EGR) Valve -Corrected Linear Lift Position"-- 0%-This value never fluctuates, it is always 0
"Differential Pressure Feedback EGR(Exhaust Gas Recirculation)Sensor - Raw" -- fluctuates between -3.70 to -3.40
These readings are during 45 minutes of variable driving on several occasions. Could I have an electrical problem? These numbers are nowhere near some I have seen on here as examples So, where do I go from here? I don't know exactly what these numbers are telling me. Am I looking at the right PIDS?

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[afbryant]

The "Differential Pressure Feedback EGR(Exhaust Gas Recirculation)Sensor - Raw" -- fluctuates between -3.70 to -3.40 is in KPa .I forgot to put the UOM in.

 

[RangerBill]

For the last couple of months, I have been having the bucking/surging in low gears. Been getting codes P0402, P139A and P139C. I have already tried two new DPFE sensors. After installing the sensor, I will clear the codes and they are back after a couple drive cycles. I have been only getting P139C recently. I know the basics of how to use an OBD scanner but I just got a tablet style diagnostic scanner and I am just learning the language , so bear with me
I have been checking out Live Data and it is showing:
"Desired Position of Exhaust Gas Recirculation (EGR) Valve"---0.00% -All the time, This value never fluctuates, it is always 0
"Position Sensor A Of Exhaust Gas Recirculation (EGR) Valve -Corrected Linear Lift Position"-- 0%-This value never fluctuates, it is always 0
"Differential Pressure Feedback EGR(Exhaust Gas Recirculation)Sensor - Raw" -- fluctuates between -3.70 to -3.40
These readings are during 45 minutes of variable driving on several occasions. Could I have an electrical problem? These numbers are nowhere near some I have seen on here as examples So, where do I go from here? I don't know exactly what these numbers are telling me. Am I looking at the right PIDS?

Here is the shop manual info for those codes.

Gasoline Engines PCED
P139A - EGR Sensor C Hoses Reversed

Description: ​	At idle, the exhaust gas recirculation (EGR) monitor commands the EGR valve closed and checks the differential pressure across the EGR tube orifice which should be zero to indicate the hoses are connected and not restricted. This DTC sets when the differential pressure indicated by the sensor exceeds a maximum threshold or falls below a minimum threshold.​
Possible Causes: ​	The upstream hose is disconnected The upstream hose is restricted The downstream hose is disconnected The downstream hose is restricted The upstream hose and downstream hose are reversed Restricted or damaged EGR tube
Diagnostic Aids: ​	Look for signs of water or icing in the hose. Verify the hose connection and routing. Check the differential pressure feedback EGR sensor for correct mounting and function.​
Application ​	​	Key On Engine Off ​	Key On Engine Running ​	Continuous Memory ​
All​	​	GO to Pinpoint Test HE .​

P139B - EGR Sensor C Upstream Hose Off Or Plugged

Description: ​	At idle, the exhaust gas recirculation (EGR) monitor commands the EGR valve closed and checks the differential pressure across the EGR tube orifice which should be zero to indicate the hoses are connected and not restricted. This DTC sets when the differential pressure indicated by the sensor exceeds a maximum threshold or falls below a minimum threshold.​
Possible Causes: ​	The upstream hose is disconnected The upstream hose is restricted Restricted or damaged EGR tube
Diagnostic Aids: ​	Look for signs of water or icing in the hose. Verify the hose connection and routing. Check the differential pressure feedback EGR sensor for correct mounting and function.​
Application ​	​	Key On Engine Off ​	Key On Engine Running ​	Continuous Memory ​
All​	​	GO to Pinpoint Test HE .​

P139C - EGR Sensor C Downstream Hose Off Or Plugged

Description: ​	At idle, the exhaust gas recirculation (EGR) monitor commands the EGR valve closed and checks the differential pressure across the EGR tube orifice which should be zero to indicate the hoses are connected and not restricted. This DTC sets when the differential pressure indicated by the sensor exceeds a maximum threshold or falls below a minimum threshold.​
Possible Causes: ​	The downstream hose is disconnected The downstream hose is restricted Restricted or damaged EGR tube
Diagnostic Aids: ​	Look for signs of water or icing in the hose. Verify the hose connection and routing. Check the differential pressure feedback EGR sensor for correct mounting and function.​
Application ​	​	Key On Engine Off ​	Key On Engine Running ​	Continuous Memory ​
All​	​	GO to Pinpoint Test HE .​

Could be the DPFE hoses are reversed or plugged tubes or hoses to the sensor.

 

[airline tech]

We need to isolate if you have a (VREF) issue or a clogged tube.
With Key (On) Eng off - What is the Voltage Reading and the DPFE (Pressure) Reading
-3.4 to -3.7 Kpa is too much (Neg) Pressure - the EGR Valve will not open to protect the engine.
You either have a (Bad Sensor, Bad VREF Circuit or the Tube is Clogged)

The (IMPORTANT) reading here for direction is (KOEO) Key On - Engine Off - Is it reading pressure?
The Pressure - Must Be (0)

 

[airline tech]

Are you 100% - Positive you do not have the hoses reversed and installed incorrectly to the tube?

 

[airline tech]

I forgot to add the DPFE Voltage @ KOEO should be 1.5 Volts & O KPA or PSI

So (0) Pressure = 1.5 Volts a slight variance such as 1.49 Volts may be seen

Ensure you do have the Hoses (Crossed)
Ensure the (Small) Upstream Port is not clogged
Ensure the KOEO (Key On Engine Off)- Readings above are (True)
If the above is all good, then it's a clogged orifice (inside the tube) as the most likely

So, if you ref the diagram below:
Note: Pressure Inside the Tube is (Equal) when no EGR is Flowing, so you are seeing (if hoses are not reversed) a blockage in the tube between the (Lo & Hi) pressure ports and the one that will drive the (-) Pressure reading so high is the (Upstream) port or orifice being clogged.

 

[afbryant]

OK guys,Correction-the UOM is PSI and NOT Kpa, but the numbers are right. I sincerely thank you guys for your help
With the key on engine off:
"Differential Pressure Feedback EGR(Exhaust Gas Recirculation)Sensor - Raw" is -3.67 PSI
"Voltage Of Exhaust Pressure Sensor" fluctuating from 0.997 to 0.999 V
valid question about the reversed hoses, that is exactly what i thought after the first time. I had to check behind myself but i had them right. I have had the DPFE/hose assembly on and off I think 4 times now but always this same result.

 

[My12SecRanger]

I had to use shop air and blow thru the egr tube fittings where the dpfe connects, the smaller hose was partially clogged on my truck

 

[airline tech]

OK guys,Correction-the UOM is PSI and NOT Kpa, but the numbers are right. I sincerely thank you guys for your help
With the key on engine off:
"Differential Pressure Feedback EGR(Exhaust Gas Recirculation)Sensor - Raw" is -3.67 PSI
"Voltage Of Exhaust Pressure Sensor" fluctuating from 0.997 to 0.999 V
valid question about the reversed hoses, that is exactly what i thought after the first time. I had to check behind myself but i had them right. I have had the DPFE/hose assembly on and off I think 4 times now but always this same result.

The Exhaust Pressure sensor is (NOT) the PID you want, that is an entirely different sensor.
It's going to be (DPFE) Voltage, note not all scan tools will show both the (Voltage & Pressure)
I am curious if you were to disconnect the hoses will it read the same - if it does then it's the sensor itself of wiring, being that the sensor has been previously replaced - I am leaning towards wiring -more likely the (Signal Return - or Ground)

 

[airline tech]

I am working on a T-Shoot flow chart, but first:
If you disconnect the Hoses - Does, the PID Reading change?
If you disconnect the DPFE Connector - Does, the PID Reading Change?
Looking for both DPFE Pressure and DPFE Voltage if the tool will display both.

The results will confirm (Clog) or (Sensor) or Wiring Issue and if wiring I highly suspect it's on the Signal Return - Circuit - Contaminated by the wiring or another sensor on the signal return circuit.

 

[afbryant]

I could not find the DPFE voltage on this scan tool. It is a sorta entry level diagnostic tool but it does have a couple more EGR PIDS.
I will try to get out there and disconnect the hoses tomorrow hopefully. Working 12 hrs next few days. Thanks again for your time

 

[RangerBill]

I could not find the DPFE voltage on this scan tool. It is a sorta entry level diagnostic tool but it does have a couple more EGR PIDS.
I will try to get out there and disconnect the hoses tomorrow hopefully. Working 12 hrs next few days. Thanks again for your time

Have you tried reversing the hoses to the sensor? Have you verified that the hoses and tubes are clear and not clogged?

 

[afbryant]

Ii have not tried reversing them yet,...that has crossed my mind. That shouldn't hurt anything if only temporarily,right?)
I cleaned the hoses and stuck a coated wire down the tubes as far as it would go. They seem clear other than a light oily residue

 

[RangerBill]

Ii have not tried reversing them yet,...that has crossed my mind. That shouldn't hurt anything if only temporarily,right?)
I cleaned the hoses and stuck a coated wire down the tubes as far as it would go. They seem clear other than a light oily residue

It shouldn't hurt anything for a trial. After switching them, clear the codes and check for codes after a drive.

 

[afbryant]

I took off the hoses at the DPFE an ran live data with Key on engine off and it read -3.65 PSI, basicsally the same. I hooked up the OEM FoMoCo DPFE sensor. It read -0.38 to -0.43 PSI
I hooked up a third DPFE sensor and it read -3.63 PSI. All of these readings are with no hoses on. I checked each one twice. This is PID:
"Differential Pressure Feedback EGR(Exhaust Gas Recirculation)
Sensor - Raw" I will reverse the hoses and try that tomorrow

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