P0471 even after DPFE, EGR, and EGR tube (cleaned)

[burrboss]

I'm sort of at a loss I keep getting a P0471 code. I've replaced my DPFE sensor with the ford OEM one which cleared the code for about 200 miles then it came back. The check engine light will go away and come back about every 50-100miles now so I decided to take off the EGR tube to do a complete cleaning. Tons of build up inside but I think I was able to get most of it out with parts cleaner. While that was off I also replaced the EGR.

Check engine light went off for about 50miles and just poped up again. Anything else I should check or any suggestions? Borrowing my friends Autel MaxiCheck scanner if anyone has any suggestions on what I should be looking for.

Thanks

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[airline tech]

You need to move in another direction - P0471 is for the Exhaust Pressure Sensor, not seeing the proper pressure reading above - Barro & MAP.
This is not the DPFE Sensor.
The Exhaust Pressure Sensor is mounted on the EGR Cooler (Outlet) Bung in between the EGR Cooler and the EGR Valve.
So, if you replaced the EGR Valve, the sensor is right next to it.

With Scan Tool: ----KOEO- Key On Engine Off
Look at these PIDS:

Barro
Exhaust Press Sensor (PSI)
Map Pressure
All The Pressures - Should Match (Approx 14.21 PSI)

Start Engine and @ Idle
Check the same PIDs

Barro - will stay @ 14.21 or whatever you have (Approx Range -14.2 -14.5 PSI)
Exhaust Pressure Sensor: (Approx 15.09 PSI)
Map Pressure (Approx 5.7 PSI)

Snap-Throttle to (1500-2000 RPMs)
Exhaust Pressure should (Quickly) Climb and Not Lag or Slow Response
Ref: At 2,000 RPMs it should read (Approx 15.76 PSI)

The sensor uses the Barro as a Ref for (Engine Off) Base - Pressure and should match Barro at KOEO.

When the engine is running it measures the exhaust flow (aka Back-Pressure) if the PCM determines the (Ex Pressure is too low) it will not command the EGR Valve Open, as it determines that there is not enough pressure to produce (EGR-Enrichment)
So, you are looking for (pressure rise above barro)

Possibles:
1. Sensor is bad
2. Wiring is bad (VREF Circuit)
3. Clogged (EGR Cooler) Bung for the Temp Sensor, note this does not mean the EGR Cooler is clogged - it's just the Pressure Pickup Tube with only that code.

Perform the Scan Tool Tests:
If its reading (bad) pressure at KOEO vs Barro - Suspect Sensor
If the KOEO Reading is good (Press & Barro - Match) suspect Sensor or Clogged Tube

Pull the sensor and inspect the short tube feeding down to the EGR Cooler, I tried to find a pic of this pickup to visually see - Full Diameter Tube with a threaded boss or is there a small diameter restriction built into the tube - No Luck finding a pic.

This is a common - confusion point - Exhaust Pressure on the Ranger has 2ea Sensors.
They both tie into the EGR Flow.
Exhaust Pressure Sensor - Mounted Before the EGR Valve - Measures Exhaust Pressure
DPFE Sensor - Mounted After the EGR Valve - Measures EGR Flow

So, it's basically this: The Exhaust Pressure (Ex press Sensor) provides the Pressure feed to the EGR Valve - when it opens - that pressure (depending on EGR Valve Commanded) open is then fed to the DPFE sensor - then the DPFE sensor (feedback) of that pressure if it does not see the expected reading (press) the PCM commands the EGR Valve to a greater (% Open) and this is where the DPFE - FAILS, however it takes the Exhaust Pressure (itself) to produce the flow.

 

[burrboss]

Below is what I got for readings. I'm assuming the sensor is bad since the EPS is a few PSI higher then Barro. Also when I rev the engine EPS stays around 17psi and only moves up 1 or 2 PSI if I go to like 3500 RPM

Key On Engine Off
Barro = ~14.3
Exhaust Pressure Sensor =~16.88
map = ~14.58

ENGINE on at idle
EPS = ~17.2
MAP = ~4.57

ENGINE~2000 RPM
EPS = ~17.1
MAP = 5.69

I appreciate the advice!This is all a bit confusing to me but your write up was very helpful. Let me know if i'm misinterpriting what you said. Going to purchase the sensor tomorrow

 

[airline tech]

Below is what I got for readings. I'm assuming the sensor is bad since the EPS is a few PSI higher then Barro. Also when I rev the engine EPS stays around 17psi and only moves up 1 or 2 PSI if I go to like 3500 RPM

Key On Engine Off
Barro = ~14.3
Exhaust Pressure Sensor =~16.88
map = ~14.58

ENGINE on at idle
EPS = ~17.2
MAP = ~4.57

ENGINE~2000 RPM
EPS = ~17.1
MAP = 5.69

I appreciate the advice!This is all a bit confusing to me but your write up was very helpful. Let me know if i'm misinterpriting what you said. Going to purchase the sensor tomorrow

Yes- The Ex Press sensor should be reading very close to the Barro / Map Pressures @ KOEO, the same as the Barro / Map (Readings) are.

The @ idle reading should be (Slightly) above the Barro - 17.2 is too high
From idle to 2,000 RPM - the Ex Press - Decreased - It should slightly rise

So, the sensor is skewed (high) - when you pull it out - inspect the (Bung) and clean it (if noted) carbon build-up. (Replace Sensor & Clean Tube)
If this does not - bring the readings back to normal - then it's in the VREF circuit.

Note: My MAP Reading was at 2,000 RPMs (But under a Brake Pedal Hold) test, so that is why my MAP Pressure @ 2,000 RPMs was higher - sorry I did not think of that - You MAP is normal @ 2,000 RPMs and just throttle raise.
But we can verify that the Ex Press Sensor - Is not correct @ KOEO

You are looking for:
KOEO - Match the Barro & Map Closely
Idle - Slight increase above Barro
2,000 RPMs - Slight Increase over (idle) Reading

 

[airline tech]

I was thinking on this - and to help isolate clogged tube (Bung) or sensor. Remove the sensor and see if the pressure goes to normal.
If it does then the tube is clogged (trapped) pressure. (Leave connector connected)

 

[burrboss]

I was thinking on this - and to help isolate clogged tube (Bung) or sensor. Remove the sensor and see if the pressure goes to normal.
If it does then the tube is clogged (trapped) pressure. (Leave connector connected)

Pressure was still off once I removed the sensor and left it plugged in so im guessing sensor.

I have now replaced the sensor and all data looks normal! Check Engine light has turned off as well. Going to be driving around 200-300 miles over the weekend. Ill post an update if I run into any other issues with the EGR system. Heres hoping that the issue is resolved!

I appreciate the help!

 

[airline tech]

Pressure was still off once I removed the sensor and left it plugged in so im guessing sensor.

I have now replaced the sensor and all data looks normal! Check Engine light has turned off as well. Going to be driving around 200-300 miles over the weekend. Ill post an update if I run into any other issues with the EGR system. Heres hoping that the issue is resolved!

I appreciate the help!

Awesome

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