hello friends how are we all doing? just had few questions hope you all could help me out. Got my truck and got three codes PO136, PO141, PO401 what should i do. thanks in advance for your help.

 

Code P0136 and code P0141 are both downstream O2 sensor circuit codes on bank 1 or in laymens terms faults with the O2 after the cat on the passenger side. Could be a true sensor fault or a byproduct of code 401.
Code 401 is EGR insufficent flow. Which is very common on the 4.6. What happens is that the two EGR ports in the TB like to stop up with carbon.

It would help to provide some more info like year, model, engine mileage, etc.

I was thinking that maybe it is carboned up setting a code 401 and for some reason the O2 sensors sinced a problem with the air'fuel ratio fue to the EGR system not working right. But that should have set a code P0171 or P0172 for lean or rich not the P0136 which is senosr fault or code P0141 which is the heating circuit of the O2. It's strange for a downstream sensor to go out before a upstream sensor. It could very well be both things could have happened.

You may try clearing the PCM (pull the batt cables) and see if it will reset itself. If not remove and clean TB and try again, if that fails replace the O2.

 

thanks for your reply my truck is a 97 f150 4.6 engine i have 227010 miles i also have changed both front o2 sensors because thats what autozone had told me was wrong but still got check engine so i bought my one codereader and got these three codes ive tried reseting the com by disconnecting the battery but no success hopefully this helps thanks again KYFordFreak

 

I would almost be 100% then that your EGR passageways in the TB are clogged setting the code 401 and causing a bad air-fuel mixture some how some way. I may be wrong but with that many miles it's not going to hurt to pull the TB off and give it a good scrubbing.

 

Rub, before pulling anything apart I would take the vacuum line off the EGR valve and with the engine idling, hook up a vacuum gun to the valve and apply about 5in. of vacuum. If the engine stalls or runs very rough then the EGR valve and the ports are fine, and you may simply have a bad DPFE sensor, a broke vacuum line, or a bad vacuum solenoid.

 

I have this same problem same truck 97 4.6l.
Codes are 401 and 141 after reading these old post I'm pretty sure it's the problem.
I have removed the vacuum line to the EGR and applied vacuum the truck lost a couple RPM'S but still ran smooth not even close to stalling out.

My question is when you say "TB" you mean Throttle Body? and what exacty should I be taking apart and scrubing. Any tips from somone who has done this repair before would be most helpful.

Thanks in advance

 

I tried to find the thread with the details here, but have not had much luck yet ( pinging and a 4.6L ), which shows great detail on cleaning the ports in the Throttle Body ( that is the TB abbreviation )

Here is a thread that links to another site, on cleaning the TB, and shows the clogged EGR ports, that temp1 posted:

https://www.f150online.com/forums/sh...d.php?t=234922

The old thread that I have been trying to find describes the DTCs and functional problems when the EGR ports get clogged, one of them is a pinging, the other is for P4xx codes ( some have reported, not my personal experience ).

I don't know if this is what others were getting at with the posts in this thread or not.

If you do a search on P0401 and P0441 you will return a ton of threads on the topic, along with the postings from the factory service manuals ( if you do an advance search and use my S/N ) on what the diagnoses steps are, and have been so far.

Good luck, let us know how it turns out ( for the next member with the same problem ).

 

Thanks for the link.

I cleaned the Throttle Body one of the EGR ports was totally pluged and the other was very close to it.
One thing I learned is to not drop your new EGR gasket into the black hole directly under it. I spent a while fishing it out I had to use a magnet attached to a fish tape, through the passenger front side of the motor to get it out.

But over all easy to clean.

The truck runs much smoother but I'm not sure if it will fix both the codes po141 and po401. "It had to help something"

I did not reset the codes because I'm not sure how to without a scan tool. the chilton manual says not to disconect the battery to reset the code, so I didn't.
Also when I was checking the EGR valve selonoid the Chilton book say you should not be able to blow through it. When I blow through the upper (green line) I can but not through the lower? (white line)

Anyway I will post back after I drive it around and hope it clears the codes.

Thanks a bunch

 

Disco of the battery will clear the codes ( P04xx ) and set the P1000 DTC, which is tests have not completed. The scan tool will allow you to clear individual codes one at a time.

Here is a link to the drive cycles, needed to clear or reset a DTC :
http://www.obdii.com/drivecycleford.html

The speed needed in each of the 2 to 3 drive cycles is 47 or 48 mph at a min.

Remember steady foot is the key for the whole drive cycle, when you WOT, you are running the DMAP settings from the PCM, not closed loop control.

Either way, take a trip around town, up to ~ 50 mph, back down, etc. Mike Troyer has a good outline, that I cannot find at the moment, for post tune install drive, that covers the full drive cycle. If I can find the text I will post it.

The EGR valve is a one way device ( best I can recall from the back of my mind ), so only blowing through it one way is ok ( again best my feeble mind can think up for the moment ).

 

OK here's the poop

Yesterday at lunch I Disco'ed the Batt, light went out then came back on the way home. I got home read the previous post (thanks sscully) and learned I scewed up, fuel was close to empty and I had to almost go to WOT entering the freeway.
So I went to the gas station cleared code again and put in a fresh tank of gas I went over the 3/4 mark closer to F. Anyway, I drove it around a little, then to work this morning about 40 miles then at lunch it came back on. I tested the EGR by applying vacuum work as it should.

So now I'm not to sure I may just try again to clear it now thats it's at the 3/4 mark. If that don't work replace the DPFE and the EVR ?

The trucks got 185K and the parts are inexpensive so it may be worth it to replace them.

 

You can try that, but I am guessing if you did the second drive cycle correctly, you might still have a problem with something else, aside from the one clogged port.

If you have time, do the drive cycle on it ( if you already disco'd the battery ) and stop by and get the codes scanned again, now that you know the EVR and the ports are ( should be ) good.

Let us know what DTC you are getting ( or the same, if it that ) and we will go from there.

You can start swapping parts, but I would rather take a diagnoses route to it, as you never can tell how many "cheap" parts you are going to swap out, maybe for no reason. It could add up quick.

At least that is my thought on the topic.

 

I'd replace the DPFE but I see no indication at this point that the EVR is defective.


Steve

 

I have seen very few EVR's thatare really bad . Almost always the DPFE.
At idle, Differential Pressure Feedback EGR (DPFE) voltage should be .5 - 1.2 volts. When opening the Exhaust Gas Recirculation (EGR) valve at idle, the Differential Pressure Feedback EGR (DPFE) sensor voltage should increase to over 4.0 volts and the engine RPM should drop severely. If the sensor voltage does not change sufficiently but RPM change is severe, the sensor has failed.

 

I just had the codes pulled again and the po401 is gone, but the po141 is still alive and well, o2 sensor heater circut malfuntion bank 1 sensor 2.

I have read on here that the rear sensor seldom go bad before the front, should I replace it anyway?

 

Check resistance of the heater element at the sensor(3-30 ohms on the two white wires at the sensor). Check the RD wire at the oxygen (O2) sensor connection for battery voltage on the harness connection with the key on. Check the WT/BK wire for an open or short to ground between the oxygen (O2) sensor and Powertrain Control Module (PCM) pin #95.