"DEF low, but you know it's not" problem

Hammerhead wrote:
It's nice to actually see the trees so DEF systems aren't all bad.

ACZL wrote:
Sadly, it's not problems w/ any of the big 3's engines. Rather the DEF system is going to be the Achilles heel going forward. Semis are no different. Can thank our tree huggers for this.

Are you saying that you could not see the trees before DEF systems came on the market?

DmaxWW wrote:
My 2011 had the same problem twice now in 40k miles, both times it took a complete system replacement. Asked the Service Manager if this was going to continue or if Chevy had fixed it, his answer was, you can continue to expect problems and once out of warranty plan on 2k per occurrence.

That's reassuring.

SCR systems using urea have been used for a lONG time in stationary power plants. It's a pretty proven technology for those applications.

for trucks and cars, yes there have been teathing problems transferring the technology. Personally I'm not worried. my new truck gets about 2-3 mpg (10% better) better than the 04 unloaded on the highway, with 800 lbs more weight and 100 more horsepower, cleaner running, quieter.

ACZL wrote:
Sadly, it's not problems w/ any of the big 3's engines. Rather the DEF system is going to be the Achilles heel going forward. Semis are no different. Can thank our tree huggers for this.

Actually the emissions systems on the trucks are not added just to save the environment and this is a very common misconception. Emission devices like DPFs are there to save your lungs. Diesel particulate matter is very carcinogenic (causes cancer) and has been proven to cause a wide array of respiratory issues. You may not see any immediate negative effects of breathing in black diesel soot, but the very fine particles attach themselves to your throat and lungs causing long term effects. Not only that, but it also costs the taxpayer and those with health insurance dearly since they(we) are the ones picking up the tab for those affected by particulate matter. Remember that the next time you see someone "rolling coal" around you. He not only is increasing your chances of lung cancer, but he is also costing you money by making you pay for those affected through higher health insurance payments or tax money going to elderly Medicare patients. ALl that just so he can look cool.

Also, the DEF system is actually the saving grace for the new diesels. Without the SCR/DEF system, these engines would have to rely solely on the EGR system to removes NOx. The EGR lowers NOx by introducing cooled exhaust gas back into the intake lowering combustions temps which is not ideal for a diesel to run at its peak efficiency and optimum performance which lowers the life of a diesels engine. Cooler combustion temps also creates more soot/particulate matter clogging DPF often. With the SCR/DEF system, the engine does not need to utilise the EGR as much to lower NOx since the SCR removes it by turning it into nitrogen and water vapor. This allows for diesel engine makers to increase the combustion temps and not having to dump cooler exhaust gases into the intake all the time which increases power and efficiency. The SCR/DEF systems are actually the saviour to modern diesels rather than the "achilles heel" that many mistake it for.

ACZL wrote:
Sadly, it's not problems w/ any of the big 3's engines. Rather the DEF system is going to be the Achilles heel going forward. Semis are no different. Can thank our tree huggers for this.

This comment is what got me thinking on this...

Am a technologist and generally speaking...design stuff and part of
that is to solve problems along the way to get to whatever marketing
is telling engineering departments they want to sell...

All light sources has some UV content and dependent on the materials
those designers employed...phosphorous is the main material that
has the source light waves strike to glow and produce white light
More will convert more to white light and the evenness of the coating
dictates how much UV might escape

Some UV does get through and is up to the designers' specification

Think tannin booth lights...lots and lots of UV

Now the controls side...

If optical, how did they do it?

Am most familiar with a side mounted sensor at the 'minimum' level
they wish to tell the computer...but with comments of 'full' and
non-linear gauge readings...tells me either a couple side optical
(more $$$) or one that shines up/down to reflect off of the surface

Tough, as the water line/surface is NOT always smooth, but with
waves & disturbances from the road surface

Hysteresis is how that would be muted a bit and fits comments of
how slow the gauge readings are


If floats, then that too need hysteresis as it will rock up and
down from the waves/disturbance

But floats do sink. Partially to all the way...


If optical...is it on constantly? or do they pulse it on some
time cycle?


Noodling this some more...most likely a float...optical is too
expensive and maintenance issue if the liquid has a coating/clouding/etc
portion of their life cycle to coat the lens...why spark ignition
never got going...the lens/window clouds up...

PS...also thank the tree huggers for removing 'some' the 'brown'
from the sky...

I've had asthma since a kid and my last trip to see my grandson
in S Cal...had several attacks due to the higher levels of SMOG
down there...so I do appreciate what the Tree Huggers have done

Just look up 'smog', 'images' and 'china' and/or 'India" and you
might remember what many urban areas in NA looked like in the 60's
and 70's

In China...the government stopped all traffic into the capital
'cuz of smog. Some were stuck there for up to 4 days...the gov
also banded private vehicles in the city during the Olympics
so that the foreigners would NOT see the typical smog...

DmaxWW wrote:
My 2011 had the same problem twice now in 40k miles, both times it took a complete system replacement. Asked the Service Manager if this was going to continue or if Chevy had fixed it, his answer was, you can continue to expect problems and once out of warranty plan on 2k per occurrence.

Ouch....

BenK wrote:
Reason asking is that am thinking DEF is sensitive to light...

Optical, some, shine a light into the bottle via a special plastic lens that
has an angled cut

That angle has the light bounce enough back if not submerged to tell the
computer the level is below that lens

If submerged, then the angled cut will NOT bounce back light, but pass it
through into the bottle

Wondering if that light degrades the DEF

Floats have their problems too...

Ben, I'm not exactly sure to be truthful with you...The gauge in the truck is non linear and not very good....it'll stay on full for quite a while...I just topped off...showed I had a quarter of a tank and I put 4.5 gallons in, (tank holds 5.5 gallons)....I understand if level get's too low you will get a message telling you that you need to refill within "X" amount of miles.

Booklet states the DEF injection system consists of the following components:
DEF tank
DEF pump
DEF injector
Electronically-heated DEF lines
DEF control module
NOx sensors
NH3 sensor
temperature sensors
SCR catalyst.

It seems like the intensity of Direct sunlight is not good for the DEF, wouldn't think a light sensor , if that is what were to be used, could cause a break down like direct sunlight would.

I've had this truck 2yrs, 2 months and have 32,100 miles on it at this time....Have never had an issue with DEF, compariing this truck to my 10' and 12'....this truck, though heavier, get's better MPG than the other two. Never had an issue of even coming close to putting DEF in diesel fuel filler neck, nor putting diesel in DEF filler neck, (pump, small or large wouldn't be able to fit into the DEF filler neck...

I purchase my DEF at the pump...I have a truck stop about 5 miles from the house and fill up there....at $2.79 a gallon, it's cheaper than the 2.5 gallon cartons you can buy. Though, if I were to go on a long trip, I might buy one of these containers to be "better safe than sorry"...

Reason asking is that am thinking DEF is sensitive to light...

Optical, some, shine a light into the bottle via a special plastic lens that
has an angled cut

That angle has the light bounce enough back if not submerged to tell the
computer the level is below that lens

If submerged, then the angled cut will NOT bounce back light, but pass it
through into the bottle

Wondering if that light degrades the DEF

Floats have their problems too...

BenK wrote:
Question (I don't have diesel)...how does the vehicle sense DEF level

I'd like to know for all brands of TVs

Float ?

Optical ?

We're not sure. The dealer said ours has a float and some people talk about NOX sensors. Maybe someone else will chime in.

Question (I don't have diesel)...how does the vehicle sense DEF level

I'd like to know for all brands of TVs

Float ?

Optical ?