Due to the timing of the regens and where I was, the last two regens have started just before I got to my destination and had to shut the truck off. First time it just got down to 90% when I shut it off, this time it hadn't even got down to 95% yet, but I heard the popping from the exhaust after I shut it off and got out. The first time, the dash said 70% when I started it back up. This time it baked it's way down to 75% after the shut off, but it did climb back to 80% rather quickly.

Anyway, this got me thinking about how accurate this meter really is. I thought after decades of the whole gas gauge thing the DEF level would be rather simple, but we all know how less than accurate the DEF level seems to be.

Does the PCM use a similar faulty countdown when figuring who full the DPF is, or is there some actual meter that is closer to accurate?

I can't imagine my truck is smart enough to correctly figure out how plugged the DPF is, yet it's too stupid to properly gauge weather I have more or less than half a tank of DEF.

 

Let's put it this way. When the DPF says 100%, a regen starts within a few miles, so, the ECM thinks it is accurate enough.

The DEF level is has metal rods for the sensors. When uncovered, the level is reported according to that rod/sensor. The sensors are similar to the way a holding tank on a travel trailer work.

Look at the DEF tank and you can see how it is measured for the 6.7.

Coffee Table Books

 

I read somewhere that the DPF level is based off of a pressure sensor measuring restriction across the filter. I would expect it to be pretty accurate. I noticed on more than one occasion that the level upon startup after a cool down is 5% less. I figured that as the media or whatever trapped soot in the filter cools it shrinks and would become less restrictive. Who knows, just a thought.

 

I see how it's supposed to be measured with the electrodes and continuity readings converted by the PCM.

I also know I've overfilled mine twice in 16k miles because the reading is inaccurate.

I was just wondering if the PCM also gets so far off on the pressure readings from the DPF.

Sorry, but I'm kinda new to the 6.7 so I'm not as trusting with all the computer gizmos and readings.

 

IMHO, accurate enough and it's slow reacting too - kinda like the temp display... When I leave my heated garage it takes about a mile or so to reflect actual temp outside. You can now use Forscan to do a stationary regen on your own. I actually plan on doing this soon so I can get my % down as low as possible. Even when a regen starts as soon as I leave the house, it never completes, even after a 20 mile drive I have. I can get down to 40% after a hot soak. I'v noticed on more than one occasion getting an extra 10-15% reduction after I shut it off. It's not like you turn the truck off and the DPF immediately cools off. just my .02...

 

If you try to correllate the dash gage to any reading from ForScan, they will not be directly correllated. I have a constant readout of DPF load (% and g/L), DPF pressure, and anything else I can find DPF related. The dash gage is not using any of these directly, maybe a combination along with some heuristics. There is a loose correlation between all of them. Mine always starts a regen within a minute of hitting 100%, and usually gets down to around 30% before shutting off, continuing down to maybe 25% as it cools.

If I stop the truck during a regen, I don't just shut it off - I park (which will stop the regen) and let it cool for a few minutes idling.

 

I think it is fairly accurate. It does a good job while towing. When I hook up and get to temps I can watch it passively regen and get to zero and stay there.

 

Is there a thread with directions on this somewhere? Or do I just need to play around with it?

My regen always seems to stop at 20%. If I shut off not too long after that, it will be down at 15% when I start it back up, but I've never seen it work it's way below 20% on the dash. I have seen it work down to 20% and then start to climb again on a long drive.

 

Look through the 6.7 for a thread called OCR v2.0.
I'm on mobile and can't link the thread.

 

This is normal stopping point for most who have the screen enable. You are worrying about it too much. Drive the truck, enjoy it and worry about things you can control.

 

So accept the DPF readings as valid and don't worry about it at all, but realize the DEF readings are inherently faulty and don't trust those.

 

How do you know the DEF reading are inherently faulty? The ECM will let you know when you need DEF with adequate time to purchase DEF. If you read your diesel supplemental owner's guide, it will give you info on DEF usage with varying gear ratios and loads.

Personally, I check the DEF status on my IPC display at times to see if I am under a half tank but otherwise, I rarely worry about it.

Just remember the old song title....."Don't Worry...Be Happy". I bet you will be a happier camper if you just enjoy the truck and do less worrying.

 

You mean besides the numerous threads here? I've only had my truck about 5 months or so, but I've already overfilled my DEF twice. First time was when I noticed the computer telling me it was under half a tank. 150 miles later I got around to trying to add a 2.5 gallon jug. Next time was when the 500 mile countdown began. I got down to around 350 miles left and was a bit nervous in case the reading wasn't accurate so I stopped and got a 2.5 gallon jug to tide me over. Took a little less than 2 gallons before it started spilling down the side of the truck in the parts store parking lot.

My DEF reading for a 5 gallon tank is inaccurate. Two overfills in a 2 month span based upon what the computer is telling me. That's why I'm wondering about the same computer and the DPF readings.

And as for don't worry, be happy, my old truck with 560k miles got way better fuel mileage than this new one, so it's hard to be happy when I have to stop at the fuel pump so often.

 

If you read your diesel supplemental owners manual, it tell you the tank is only 5 gallon and when the best time to refill and to use the Ford PM-27-N nozzle. This helps prevent overfilling and DEF on the side of the truck. You can get the Ford nozzle on eBay for under $10 shipped to you. I have seen them for $5 shipped.

And refill it so soon? It not like you are going to run out. The readings are accurate for everyone else but you and they have learned how to handle it and when to refill so it doesn't overfill.

well....go back to your old truck then....

and go read your manuals....it a lot of info in them....if you don't have any, you can download them here...

https://owner.ford.com/tools/account...h-results.html

 

You mean after the big warning comes on and begins the countdown to de-power. Getting down to 350 miles before the computer makes life miserable is too soon? I must have missed that in the manual.

And if it's a 5 gallon tank that is less than half full, I shouldn't have to worry about any special nozzle when only adding 2.5 gallons unless you use a different math than I do.

But I'm sure it's all me. Please feel free not to assist me further on this matter.