P0402

[ericm88]

A couple week ago my '21 Ranger with 42K threw a P0402 code. The Fordpass app's recommendation to fix the code was to look for a damaged air filter or air inlet tubing. I was due to replace the air filter anyway so I did that and it didn't solve the code being thrown.

I hooked up my scan tool and had a pending code of P139C on one drive but every time the check engine light would come on it would be the same P0402 code. That pending code led me to https://www.ranger5g.com/forum/threads/bucking-surging-epidemic.14581/page-12#post-443880 .

I never experienced any noticeable bucking or surging but based on reading that thread I replaced part # LB5Z-9J433-B . After I replaced that part I tapped the old one on a hard surface and there was quite a bit of water that came out.

I didn't see any posts on this site that directly tied that code to that replacement part so I wanted to share my experience. Thanks to everyone who contributed to the surging thread as that helped me pinpoint this issue!

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[airline tech]

Yes, Pending Code P139C, is for the EGR Sensor
Downstream hose off or plugged / restricted.
The Downstream is the smaller one of the (2), it is the hose closest to the electrical connector.
Moisture buildup inside the sensor will trigger that code as well, you will most note it inside the Upstream side of the sensor, bigger tube.
The biggest issue here is that symptoms occur before it generates the code, and when it finally gets a (error difference) great enough it will pop the code.

For Reference:
P139A - Hoses Reversed
P139B- Upstream hose off or plugged / restricted.

P0402 - EGR Flow Excessive Detected
* EGR Tube Restricted (This tube is the orifice tube that interconnects both the Downstream and Upstream sides of the sensor (Measuring the Differential Pressure)
* Slow Responding DPFE Sensor
* Damaged DPFE Sensor

So this is how the (2) codes relate to each other.

 

[Chimchim]

Great info guys - I had this issue and Ford went straight to replacing the DPFE sensor, which I can only imagine is the most expensive one. I ordered the EGR Vacuum Control and was wondering if I should check anything else while I am there? Anyone have a pic or diagram to help me swap this out? Frustrating that 4,000 miles after the warranty expires and I've had it less than 2 years I'm having to fix anything, much less Ford trying to get me for $650 ..... thanks in advance.

 

[Racket]

Moisture in the EGR system? Seems like an easy to anticipate problem that Ford could have factored in to designs.

Is this validation for the catch can install since it pulls a lot of 'water' out? Or is that farther down the system path?

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