2011 F-350 P207F (again)

[billbled]

Hi guys,
Advance warning - this is likely to be a long post about P207F. Apologies for the length, but I would really appreciate any input. Several techs have worked on this truck, now it's in my bay.

One of our IMAP trucks (the "help me on the highway" trucks here at DOT) is really turning into a problem child. These trucks spend all day driving up and down highways and interstates helping motorists and crash situations. So they are either moving at 55mph or idling on the side of the road for an hour. 

The truck in question was born 5/2011, and has VIN 1FD8X3FT1BEC69479. It's a F-350, 6.7L, etc etc. Current mileage is 244,226 miles. Since we are a fleet customer (NC DOT), I have access to IDS, the PTS website, and the TEXA software from Diesel Laptops. I used to have access to the Ford technical hotline thru the PTS website, but no more. I was told that was too expensive and so they discontinued that. I thought it came with the PTS/IDS subscription, but I guess not.

History:
- 203,686 miles - they replaced #6 & #8 injectors for an engine knocking complaint. 
- 203,740 miles - it set a fault for #6 injector (P0278) and SCR below threshold (P20EE). They reprogrammed the PCM, and reprogammed fuel management, according to the R/O.
- 203,980 miles - In for P20EE (again) and P207F. Replaced the NOx sensor & module, reprogram module, reset adaptations and drove. 
- 204,043 miles - CEL on again, P207F, replaced DEF pump (failed dose test) and drained/refilled DEF tank. Checked DEF - 32%.
- 204,502 miles - back again P20EE, P207F - replaced DEF injector, removed U & L intake and decarbon, replaced EGR core and cleaned EGR valve, did SCR drive cycle, fault returned, contacted Ford tech hotline (was able to at that time, can't now) - replaced SCR catalyst assy (a.k.a. "torpedo"), reset all adaptations and monitors, test drove. Measured NOx went from avg 700-900PPM to avg 30PPM after torpedo replacement. 

- 244,226 miles - present day - P207F returns, and JUST P207F - no other faults present. Avg NOx is all over the spectrum. I've seen 300-450 all the way up to 900PPM. At normal op temp, under cruise control at 55mph, I'll see it swing from 250-400PPM avg.

I've tried:
- manual, stationary, regen
- manual, dynamic, regen
- regens were not needed according to IDS (percentage-wise) but did them anyway.
- reset DPF parameters
- swapping NOx sensor and module with another truck (same vintage) and no difference.
- reset NOx adaptations
- injector dose test (47mL)
- DEF test with refractor - measured 32%
- SCR injector was clean - no crystals seen.
- PCM programming is current
- air filter is OEM and not very dirty

Questions:
- I'm starting to wonder if two things:
1- Is the engine producing too much NOx for the catalyst to reduce? If so, this indicates an upstream engine problem. 
or 
2- Has the SCR catalyst gone bad? Seems unlikely to me. Way too soon. But if so, that's dissapointing for as much as it costs and I would hope it would have some kind of above normal warranty coverage - but haven't checked. 

Thanks for reading all this- if anyone has more ideas I'm all ears. 
-Bill

[Keith Browning]

A 2011 6.7L has only one NOx sensor which is downstream of the SCR. This means that the PCM has no idea what the NOX numbers are going into the SCR to begin with so your thoughts on the engine emissions control (EGR) are valid.

[8WA Sman]

Can you post the mode 6 data?

[JoeR]

2 hours ago, Keith Browning said:

A 2011 6.7L has only one NOx sensor which is downstream of the SCR. This means that the PCM has no idea what the NOX numbers are going into the SCR to begin with so your thoughts on the engine emissions control (EGR) are valid.

Regarding the high NOX because of EGR, are you sure on that Keith?  While I'm no expert on the Ford 6.7, any other diesel I've come across stops adding EGR once the SCR system is active.  While I believe it's possible, I'd be really surprised if Ford continued to use EGR once it wad injecting DEF.  I'm definitely going to record the data on the next one I'm in though.  You've got me curious now.

Joe

[JoeR]

11 hours ago, billbled said:

 

Questions:
- I'm starting to wonder if two things:
1- Is the engine producing too much NOx for the catalyst to reduce? If so, this indicates an upstream engine problem. 
or 
2- Has the SCR catalyst gone bad? Seems unlikely to me. Way too soon. But if so, that's dissapointing for as much as it costs and I would hope it would have some kind of above normal warranty coverage - but haven't checked. 

Thanks for reading all this- if anyone has more ideas I'm all ears. 
-Bill

Hi Bill,

What were the temps of EGT 3 and EGT 4 while it was injecting DEF?  If it is making really high NOx (say 1400 ppm) and then reducing it to 400-600 ppm like you were seeing, then you'd have probably 300 degree temp rise from EGT 3 to EGT 4.  It would prove the theory of high NOx out of the engine.

If it doesn't then you are getting poor NOx reduction out of the SCR.  My next checks would be DEF Injector Spray Pattern.  It it wasn't perfect, I't throw another one at it, or swap it from your other truck.  After that I'd be running my bore scope down my EGT holes to see if I have DEF crystal deposits in the SCR or decomposition section of the torpedo.  From there I'd condemn the exhaust.  Are you using a lot of oil in that engine, or using a fuel additive that might be poisoning it? 

Joe

[billbled]

Hey guys,

Thanks very much for the replys and interest - 

Some answers (I hope) to your questions:
- Mode 6 data? Please help me out here - I'm not sure what that is. 
- Engine doesn't seem to be using an abnormal amount of oil.
- We don't use any fuel additives - it's just bulk biodiesel out of the ground. Same fuel for the entire fleet.
- I'm going to have to re-run the EGT 3/4 temp check while injecting. If memory serves, during test drives I saw EGTs around 400-480F - I know it ran up to over 1,000F during regen. 
- the max NOx I've ever seen is 900PPM
- And .... this morning I took some pictures. SnapOn BK8500 scope going down the DEF injector hole. They're on my personal site (link below) - 17 photos.....found 2 holes burnt thru the screen/grid. I can't imagine that this is OK - but now I don't know why the holes are burnt - leads me back to an engine problem? This SCR catalyst only has about 40k miles on it. 

Pics are here: https://billbledsoe.com/IMAP_1498/  

Thank you all so much for your time!

--Bill

[JoeR]

Great pics, Bill.  I may have hosed you on the EGT numbers.  Where is the DEF  located on this exhaust?  Is it closer to the front or rear of the torpedo?  The reason I ask is that your pics look like the front of the DPF, and not the front of the SCR Cat.  

If the DEF injector is located further back on the torpedo, the EGT numbers I gave you are correct.

If the DEF injector is closer to the front of the exhaust, then you need to be watching EGTs 2 and 3 instead.   

Here's the reason you're doing this.  When NOx is reduced back into N2 and H2O it makes an awful lot of heat.  As soon as that SCR catalyst activates the EGT in back of it will show it getting hot.  So it's easy to watch the DEF injector start to spray, and then you see a temp rise across the SCR cat.  The 6.7 Powerstroke has 2 different locations for the SCR Cat depending on whether it is a wide frame or narrow frame truck.  It's easy to see which one you have by looking at the DEF injector location.

Joe

[billbled]

Hey Joe,
It's on one of our IMAP trucks which is a Chassis Cab (narrow frame) - so the order from front to back is DOC / DPF / SCR - and the DEF injector (handwritten note - is where I'm going down with the borescope) is right in front of the SCR (see attached JPG).
We're currently working with the Ford dealership as it's still under its 2 year warranty, but the question we all have is *why* is it burnt? 

I'm with you on the photos looking like the DPF. I was wondering why I was seeing the grid and honeycomb, and not the red (in the JPG) DEF mixture swirl device (tornado?). Seems like I would've hit that first and stopped? Does the borescope go thru it and end up at the SCR catalyst? It was hard to tell on the screen as the camera was making its journey down the hole.  

Thanks,
Bill

 

[Keith Browning]

13 hours ago, JoeR said:

Regarding the high NOX because of EGR, are you sure on that Keith?  While I'm no expert on the Ford 6.7, any other diesel I've come across stops adding EGR once the SCR system is active.  While I believe it's possible, I'd be really surprised if Ford continued to use EGR once it wad injecting DEF.  I'm definitely going to record the data on the next one I'm in though.  You've got me curious now.

Joe

Absolutely. The diagnostics for a 2011 with a P207F have you thoroughly test for a restricted EGR cooler.

[8WA Sman]

Mode 6 data can be helpful..eg. which portion is failing and by how much, there may be other data/clues that can be helpful.

From the home screen Powertrain_OBD_Mode 6

[billbled]

Many apologies for forgetting this post. For those that are curious - the final resolution was to replace the entire SCR/DOC/DPF assembly (a.k.a. "the torpedo" - at least that's what we call it in our shop). That brought the NOx back down to where it should be, i.e.: fully warmed up truck, on the highway, reasonably level ground, on cruise at 65mph, and we'll get about 40-80 PPM NOx out the tailpipe, sometimes less. Not the 300,400,500 or more PPM of NOx that we were getting. 

Now for the details....

We purchased the SCR assembly right at 2 years ago from a local Ford dealership. When the problem started and we found the burnt up sections of the internal filter assembly, I made the pictures that I posted here and put them on a section of my personal website so the dealership guys could see. They wanted the truck back, with the defective SCR installed, so they could do their own diagnosis before replacing the filter under parts warranty.

During the *weeks* that followed, as part of their "diagnosis", they put on 2 separate NOx sensors and modules trying to correct the excessive NOx coming out of the tailpipe. They did look at my pictures, but said they couldn't see what I saw when they went down looking with their borescope. (I find this amazing since I found the internal defects very easily seen...but whatever). They were certain the NOx sensor/module was to blame, even though we had told them that we had swapped out a known good NOx sensor/module and reprogrammed and it made no difference to the NOx output prior to us delivering the truck to them. 

After more time (weeks) - several message attempts at dealership management staff, and several "spirited" discussions - they finally decided to comply with what we had originally discussed and do a parts warranty on the SCR. And then the truck was fixed. 

Why did the SCR fail? Why did it have the burnt holes and melted sections? Nobody is really sure. One of the mgr's I spoke with looked the pictures and said he had seen 2 other units do that. I don't know if it really was a defect in the internal filter material, or some other defect in the filter assembly - just not sure. The truck that this is in is one of our IMAP trucks, which are the "Incident Management Assistance Patrol" trucks - they run up and down highways and interstates all day long helping with stranded motorists and wrecks and out of gas cars, etc. So they get a LOT of highway miles.  

All in all a complete P.I.T.A. - but I'm glad it's done. 

And thanks very much for all the feedback and help here - I truly do appreciate it. Apologies again for not posting the final outcome sooner. 

Cheers,
Bill

[JoeR]

Thanks for the update, Bill.  It's always nice to know how it turned out.

Joe

[mchan68]

I once had a 2014 truck that needed not one, not two, but THREE SCR replacements to correct a recurring P207F. And they all failed at similar mileage apart from each other. The only thing unusual with this particular truck was the unusually high hour count. After the third SCR replacement, the owner finally heeded my previously repeated advice to get out of it, and into Super Duty with a gasser instead.

[Mike B.]

A lot of great info in this post. My truck is a 2011 250 lariat 100k miles with p207f contaminated def fluid message. I am a Ford employee so I have access to tech site and IDS. What would I look at in the mode 6 data that would help me diagnose. I went through the pinpoint test and at the point in the test to change the catalyst. Its on my dime so I am cringing. Good info on monitoring the EGT sensors i was unaware of that sure wish there was a NOX sensor at the front.

[Mike B.]

I had noticed when I monitor the NOX pid at idle it's roughly 220ppm when I accelerate it jumps up to 900 and tapers back down to 250-300 ppm. I have been looking around other forums relating to NOX reading this is the only post that mentions it. I would guess those are bad numbers. I also noticed the def injector duty cycle is zero at idle and seems to correlate with acceleration. At idle is the catalyst supposed to take care of the NOX emissions without DEF? 

[Keith Browning]

3 hours ago, Mike B. said:

I had noticed when I monitor the NOX pid at idle it's roughly 220ppm when I accelerate it jumps up to 900 and tapers back down to 250-300 ppm. I have been looking around other forums relating to NOX reading this is the only post that mentions it. I would guess those are bad numbers. I also noticed the def injector duty cycle is zero at idle and seems to correlate with acceleration. At idle is the catalyst supposed to take care of the NOX emissions without DEF? 

 

Mode 6 - NOx Catalyst Conversion Efficiency.

Those numbers are high. As you mentioned in your first post there is no upstream NOx sensor on a 2011 which makes diagnosis a bit more difficult because you have no idea if the EGR system is doing it's job effectively not can you or the PCM truly determine if the SCR catalyst is simply not efficient.

Since you have access to the information and IDS I recommend starting with pinpoint tests RD as per the chart. If there are no OTHER codes you will be going through pinpoint tests RK

When I begin diagnosing this code I actually prefer to jump ahead to the SCR Dosing Test because the exhaust is smokin hot from the testing leading up to it.  I like knowing the injector is working and delivering the correct amount from the beginning and if it works you also have a quick sample to inspect and perform a quality test - requires a DEF refractometer.

[billbled]

22 hours ago, Mike B. said:

I had noticed when I monitor the NOX pid at idle it's roughly 220ppm when I accelerate it jumps up to 900 and tapers back down to 250-300 ppm. I have been looking around other forums relating to NOX reading this is the only post that mentions it. I would guess those are bad numbers. I also noticed the def injector duty cycle is zero at idle and seems to correlate with acceleration. At idle is the catalyst supposed to take care of the NOX emissions without DEF? 

Hey Mike,
Ditto Keith's advice from above this post. Also, the range of numbers (for a correctly operating system) I've seen several times are what I had posted previously:
"That brought the NOx back down to where it should be, i.e.: fully warmed up truck, on the highway, reasonably level ground, on cruise at 65mph, and we'll get about 40-80 PPM NOx at the tailpipe, sometimes less. Not the 300,400,500 or more PPM of NOx that we were getting."

That's kind of been my standard test for this fault: warmed up truck, someone else driving, me monitoring PIDs, interstate travel, level ground, constant speed, and you should see 40-80PPM. On the bad DOC/DPF/SCR assy it was running at 500+ frequently, if not most of the time. 

But Keith is correct on working through the testing, and I like his idea of doing the dosing testing FIRST, while temperatures are civil and not sun-like. We still do the testing routine rather than just throwing a $3,000+ torpedo assy on it. 

Maybe Joe Rappa can chime in on this further, but he's got an exhaust sniffer that we used to verify that what was coming out of the exhaust **actually** lined up with the PID readings we were seeing, and it worked great. I don't think there are many diesel exhaust sniffers out there that measure NOx in real-time, but the one Joe brought and used worked great. It was helpful to know that the NOx emissions at the tailpipe really were screwed up and not just a software or PID error of some sort. A "second opinion" of tailpipe emissions. 

FWIW, Ford told me at one point that "life expectancy" on these torpedo assemblies was about 125k miles. I would suspect that varies greatly depending on useage, idle time, percent highway miles, etc. We have many IMAP trucks that have 200k on original torpedos, but they run highways and Interstates all day long.  

[Mike B.]

I had to order a refractometer to check the DEF fluid and it came out spot on 1.5 Oz came out and the spray pattern looked ok, first one I have done so just looking at it logically. I followed the pinpoint test up to the point of RD11,the nox sensor is changed, tomorrow I am going to do the scr system procedure drive and see what happens 

[Mike B.]

I did the manual regen and took the truck for the scr drive cycle 2 days in a row and the p207f has not popped yet. I did notice as the truck is driven and monitoring the nox numbers during acceleration the number climbs as it climbs the Def injector duty cycle does as well and it starts knocking the nox number down. I will continue to drive it and we will see what happens. Thank you gentlemen for responding to me and offering info and help I do appreciate it.