Engine Light Code

[Kodiacnb]

Just saw an engine light code on my 21 Ranger. 61000 Km (Canada) And pulled a P0402 Code. I read about it in the forums here and was just wondering if the (FMPP) Ford Motor protection plan covers this? Any info would be appreciated.

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[RangerBill]

Just saw an engine light code on my 21 Ranger. 61000 Km (Canada) And pulled a P0402 Code. I read about it in the forums here and was just wondering if the (FMPP) Ford Motor protection plan covers this? Any info would be appreciated.

P0402 Excessive EGR Flow detected.
It might be a bad EGR DPFE pressure sensor. It seems to be a common issue. Most don't get the code but some do if the sensor is especially bad. It is a $20 part from RockAuto. I would think that the Ford plan should cover it, but many have changed it themselves. The Standard Motor Products seems to be the OEM for the part.
https://www.rockauto.com/en/catalog...sion,egr+pressure+feedback+(dpfe)+sensor,5088

See this thread:
https://www.ranger5g.com/forum/thre...mbly-replacement-write-up-lb5z-9j433-b.29247/

Symptoms are engine surging during low speed and light throttle.

 

[Kodiacnb]

Right now, the truck works fine, Just the engine light but was told by the dealer it will be fine until my appointment. I had them check the code for the engine light and they pulled up the P0402 EGR "A" flow Excessive detected. I just thought if it's covered, I'll let the deal with it. If not, I'll do it myself. Thanks for the links. The write up is great.

 

[airline tech]

From my - Detailed System Operation
Not yet (100%) complete and ready for final draft.


P0402 - EGR flow Excessive – sets when the DPFE reports the signal is greater than expected at idle

P0402 Sets When:

Trigger Time 70-Seconds

Trigger Pressure / Voltage - 0.07 to 0.10 psi / 0.05 to 0.08 volts or (50 to 80 mV)

The PCM detects that the Idle EGR flow is excessive over the KOEO recorded reading

This monitor uses the same 70 seconds accumulation time as the P0401

This monitor runs at Idle only, unlike the P0401 monitor at EGR Flow

P0402 Trigger – Reading above the KOEO Learned Zero Readings (positive flow)

• 0.04 to 0.07 psi – Monitor closely watching
• 0.07 to 0.10 psi – 0.05 to 0.08 volts - Excessive Flow – accumulation zone – 70 Seconds
• Above 0.10 psi - 0.08 volts – Code automatically sets

P0402 –Possible Causes

• EGR Valve Pintle – carbon buildup under pintle – leaking
• EGR Valve – stuck open
• EGR Valve – electrical issues
• Exhaust Restriction or Cat Restriction – forcing exhaust pressure past EGR valve
• DPFE Sensor – electrical issues – false reporting
• DPFE Sensor – biased positive (Rare)
• Exhaust Pressure Sensor – Biased (altering the EGR flow monitor – Expected) see Sect 2

The Exhaust Pressure - Sensor (is just a possible (as it is only a factor in the flow monitor)

The role of the Exhaust Pressure Sensor

• The Exhaust Pressure Sensor – is not used in flow response
• Used to determine how much flow is possible for any given valve position -So it is used for the (Flow Model) not validation
• Used to calculate available exhaust driving pressure and scale expected DPFE and MAP pressure changes.
• A biased sensor can skew the expected response of the DPFE & MAP, leading to P0401 or P0402 codes along with the P139A to P139C codes.

Key Notes – Indirect Codes

The indirect related flow codes P401, P0402 and the P139 codes tie into the EGR flow monitors and the PCM is using the Exhaust Pressure Sensor as the (Master) reference point for the flow availability a biased exhaust pressure sensor reading could possibly cause downstream fault codes.

Because the exhaust pressure sensor plausibility thresholds are broader than the EGR flow verification limits, exhaust pressure bias or slow response can disrupt EGR control and set P0401, P0402, or P139-type codes without ever triggering P0471.



So by using my - Quick Ref chart I made:
Using a scan tool - pull up the DPFE sensor (Voltage/Pressure) PIDs and the (EGR Valve-Percentage - Actual & Commanded

This is the (ONLY) way to see what is actually happening - Live Data to properly diagnose the issue - however Forscan - unless it has been added does not include the DPFE PIDs and requires a high end scan tool.
Sure you can always - Shotgun the most likely part at it, I hate doing this and highly discourage it but also understand that some do not have access to the required scan tool to do it properly.

Focus only on the - KOEO - (Key On Engine Off) readings and compare to Idle readings.
The P0402 is being generated at this transition.
The DPFE is seeing a dramatic change in (Voltage) at idle over the KOEO reading - this being Learned Zero (Reference) of Zero Flow
Which should remain at - -0.06 psi or 1.48 volts (KOEO & Idle) for a perfect system operation and non biased (DPFE Sensor) which has a (variance range) incorporated into the system

and then use what triggers the code

P0402 Trigger – Reading above the KOEO Learned Zero Readings (positive flow)

• 0.04 to 0.07 psi – Monitor closely watching
• 0.07 to 0.10 psi – 0.05 to 0.08 volts - Excessive Flow – accumulation zone – 70 Seconds
• Above 0.10 psi - 0.08 volts – Code automatically sets

I am leaning more towards a bad DPFE Sensor , diaphragm sticking and will most likely be showing biased (high) out of normal range at (KOEO)

Note:
EGR System is not disabled with the P0402 Code, however the PCM may limit the EGR Desired command to (zero or near zero), this may be an indication of why you state it drives fine and the PCM is compensating by adjusting the Fuel/Spark Timing.
I do expect you are seeing a hit in fuel economy though.

The above is just a general - T-Shoot there are more in depth PIDs to look at for the complete system and I am only posting for the most likely cause - The DPFE Sensor - Itself as it has been proven to be a common failure point.

I highly recommend looking at this sensor (PIDs) first before replacing the EGR Valve.
The DPFE Sensor reading is what is triggering the code and it needs verified it is an accurate reading.
I great PID to use is the EGRT (Sensor) it can show you if EGR is actually flowing down the EGR Tube as a compare to the EGR (Open) valve position - a verification it is actually open - on a cold engine start.

I spent a great deal of time going through the system operation and Live Data Drives to confirm normal operation





As far as it be - Covered - depends on the plan level - I think - Emissions (Fine Print)

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