Check engine light

[ppfd]

Been having the “bucking and surging “ symptoms last month or so, same as a few years ago.

I figured it was the DPFE part that needs to be replaced (again). This time it threw a CEL on me.

I ran a scan and this is what it showed. Truck runs fine at highway speeds, no power lose. All the same symptoms and complaints we’ve all had related to this part.

Just want to confirm these codes are related to DPFE part.

Sponsored

 

[RangerBill]

Been having the “bucking and surging “ symptoms last month or so, same as a few years ago.

I figured it was the DPFE part that needs to be replaced (again). This time it threw a CEL on me.

I ran a scan and this is what it showed. Truck runs fine at highway speeds, no power lose. All the same symptoms and complaints we’ve all had related to this part.

Just want to confirm these codes are related to DPFE part.

Yes, P139C is related to the EGR DPFE sensor. It states that a hose is off or plugged to the sensor. Have you checked for that?

 

[ppfd]

I have the whole replacement unit.
Just wanted to make sure it’s that damned part!

 

[RangerBill]

I have the whole replacement unit.
Just wanted to make sure it’s that damned part!

Have you checked for hose blockage or a disconnected hose to the EGR DPFE sensor?

 

[airline tech]

I have dug deep into the whole EGR System, and put together a detailed overview of it - have not had a chance to finalize it - busy with summer projects (Full Kitchen Remodel) but here is a excerpt of my project which is currently @ 80 pages

P139C - EGR Sensor C (DPFE) downstream hose off or plugged (Low > High)

During idle operation with EGR commanded closed, the PCM expects the pressure at the upstream (HI) and downstream (LO) reference ports of the DPFE sensor to equalize, resulting in a differential pressure near the learned KOEO baseline. The PCM continuously evaluates the DPFE signal for rationality and monitors for excessive negative differential pressure. If the DPFE signal remains below the calibrated lower limit of (−0.58 psi) for approximately 50 seconds, indicating a sustained pressure imbalance or sensor signal outside the physically plausible operating range, the PCM identifies the signal as invalid and sets DTC P139C.

P139C sets when the PCM detects the DPFE sensor signal remains below (−0.58 psi) for approximately 50 seconds during idle conditions with EGR commanded closed, indicating an implausibly low differential pressure and a fault in the DPFE sensor or pressure reference system.

Ref the (-0.58 psi) note this is well after the buck surge zone of (-0.35 to -0.45 psi) so this highlights why the buck surge issues are experienced before the P139C code sets.

P139C sets when

Using Learned Zero – Voltage & Pressure as Ref Values

So if using Learned Zero Ref of 1.48 volts = a voltage reading of about 0.96 to 1.07 volts will trigger the code

Trigger Time Duration = 50 Seconds

Trigger Pressure / Voltage – (-0.58 psi) / 0.41 to 0.52 volts

The monitor is a continuous monitor and monitors at Idle only, no EGR flow.

The monitor is a (Negative Imbalance - Monitor) - Low Pressure > High Pressure

P139C –Possible Causes

• DPFE Sensor – internal bias failure (moisture)
• DPFE Sensor – internal diaphragm damage
• DPFE Sensor – electrical fault
• High Pressure Hose / Port – restriction – blockage
• Low Pressure Hose – leaking

Being you don't have the whole doc yet

Learned Zero = What the PCM sees as (Zero Pressure or No EGR Flow)
and what usually triggers it is (Moisture Build Up) in the EGR Tube itself , creating an offset off pressure readings - that eventually ends up destroying the internal senor


Its seeing a pressure imbalance - here, and the blue represents the moisture backup that makes its way to the DPFE sensor itself.
The (Black) lines in the tube represent the internal orifice inside the tube

Sorry I do not have the full document quite ready yet , i kina dropped the ball on it when my old laptops hard-drive crapped out

 

[Jason B]

Moisture in the DPFE sensor has been a problem all the way back on my '99 B4000.

 

[ppfd]

And just like that, the CEL went out last night and has been off since then.
I am going to replace the part either way.

Sponsored