Greetings to all,

I am a new owner of an 03 4wd with about 85k on the odometer. On the way home i The SES light comes on, about 12 miles from the dealership i bought it from. Anyway i went to autozone to have it scanned and i have the P0405. After a little research, i checked the EGR, DPFE and The 2 hoses From the DPFE. They are new, so i pulled the IAC and found the plunger to have some drag, I carefully cleaned it with intake cleaner and a little electrical contact cleaner to the shaft. The plunger was smoother, and i put it back on. I disconnected the battery cables then reconnected and the code was erased. And sure enough the SES came back on at about 8 miles. So i did the vacume test to the EGR with the truck running and the engine stutters..

So what should i check next? Assuming the EGR and DPFE are ok?

 

Typically,If the DPFE sensor is OEM, I would replace it first.In the case of my 97,the DPFE sensor was made of a metallic substance,and HEAVILY corroded.While I am a "stickler" for OEM components,I checked on RockAuto Auto Parts and found a replacement.This unit was plastic,and corrected my problem
The replacement was NOT Ford Factory,but was garunteed to meet OEM specs.
It worked flawlessly until I traded her in.

 

What i think happened is the dealership (non Ford), took the truck in on a trade, then the SES light lit, then they changed the EGR and DPFE, then cleared the code. I walked in and bought the truck, then a few miles down the road SES light is back on.

What is the chance of these parts being bad out the box?

 

Take another look at the code again!
Is it really 405?
There is no code 405 on the Ford list.
Need the correct one to see what system has the issue.
You may be chasing the wrong parts.

 

The 2003 PCED for the F-series indeed does list P0405 as a valid DTC. It is defined as "DPF EGR Sensor Circuit Low Voltage Detected "

Generally, that means either the DPFE sensor is defective, there is a wiring fault (signal shorted to ground), or the PCM is defective.

Check the DPFE sensor's output voltage (either with scan tool or meter) with the key on and the engine off. A bad sensor or circuit will read less than 0.2 volts. Normal reading from a good sensor for this test would be 1.0 volt. If the first measurement fails, unplug the sensor connector and verify that the output pin on the harness connector goes to 5.0 volts. Is so, the sensor is confirmed defective.

 

I did the voltage check and got about 5 volts, i'll change the sensor and see how it goes. Thanks for the response and i will post the results.

 

I replaced the DPFE this weekend with one from Orielly auto parts for $51.00. The SES light came back on at about 15 miles or so. I am getting about 11 miles per gallon, i suppose this is a symptom of the problem.

Back to researching!

 

You still need to read the new fault code.

 

I scanned again today, P0405 again. So if the egf and Dpfe are ok, whats next?

 

Its been awhile! from time to time i would re-dig for some information for the P0405 code and during the Hurricane break followed by a 3 day weekend, i got back on this.

to start, last week i started the truck and it would rev up, then down to kill. With a little finesse i could ease it down to an idle. i pulled the usual P0405 and then the newer P1507 and P0401. These are IAC idle too slow and Exhaust gas re-circulation low or whatever. So i decide to get a new IAC, but first i wrapped twisted teflon tape behind the rubber ring inside the gas cap to see if this would help the gas cap seal and fix the P0405. And so far the code is gone.

I installed the new BWD IAC ($93.00 Orielly) and then started the truck. The truck revs up and make a loud hum with vibration on the intake between the throttle body and the motorcraft filter. After 2-3 minutes the hum fades and i get a nice idle at about 750 RPMs. So i get in the truck and turn on the AC and the engine revs to about 2500 rpms with the AC on. I scanned for codes and found none, none pending either.

So i killed the engine, went pour some Scotch over some ice and typed this. I will see how it drives when i return to work in the morning.

 

Unless I miss understand, the 405 in not a gas cap code.
It's telling you there is an issuie with the DPFE.
My advice is to replace it with a Ford OEM part only.
The tolerences for system testing is just to tight for many after market units to pass.
Not sure if you still have a start and idle issue but the hum is very often a fitting that sings when high velocity air flows through it.
You must have changed something around it or on it.
A high idle would affect the air velocity.
I recomend you change the DPFE to the Ford unit, then remove power from the battery for a minute so a PCM reboot takes place to rebuild the start tables.
Start the motor from cold, turn on headlights, A/C , Fan on high, turn the steering wheel back and forth a half dozen times to get the powersteering load in the mix so this all places max load on the motor from the alternator and pwr steering pump.
Let it fully heat up.
Go for about a 5 mile run and back. Do several hot normal restarts.
If all is well the cold and hot starts and restarts should all be normal afterwards.
Good luck.

 

Swap BOTH the IAC valve and the DPFE sensors to Motorcraft parts.

The gas cap has nothing to do with either fault code or any observed symptoms.

 

The DPFE is new Motorcraft and i would still get the P0405, I even swapped The DPFE with my sons pickup and still 0405. I do currently believe the new IAC is bad and i will probably bring it back this afternoon, i'm not getting any codes today. Lunch hour right now.

 

If you have the 405 code even with substitution of known good DPFE, the code indictes an electical problem with the connecor or harness.
Good luck.