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Discussion Starter #1 (Edited)
P0420 - Researched to death **Solved**

Earlier this year, 20 miles before I clicked off 120k on my truck I popped a code for the DEF heater. Dealer replaced, all was good, until last week. I drive sparingly, usually to visit family or to and from the airport. On the way back from one of those trips, I popped a code P0420 for Catalyst efficiency. I reset it, came back 40mi later. After adding a bunch of the datapoints to my HP Tuners VCM scanner I noticed my DEF Tank said I was at 100% full, which was impossible because I hadn't filled it since they did the tank heater..... I always keep a couple boxes in the garage just in case so I added 2.5 gallons to the system.... still 100% and you could hear it hitting the empty tank.
I took the my laptop with and scanned again for a road test. Once it started and got under way you could see the hydrocarbon injector duty cycle 50%, while the DEF injector cycled FAST 0-15% but shows failures for pressure tests. EGT's test and show normal temps, NOX 1 and 2 only go high when I get on it hard, but I have to keep clearing the codes for the P0420 in order for the system to go into regen. Started at 48g of soot and after about 20min it was able to get it down to around 20 while driving up and down the highway by my house but reading I should probably be burning it off a little faster than that. Which leads me to believe that the DEF injector is not functioning correctly? Dealer is going to look at the level sensor tomorrow morning since that is directly related, but wondering if I clogged the DEF injector running the system dry? Could the DOC, or other exhaust parts be damaged because of DEF not being used? Sensors I can live with and replace, but if I have to go out and get a DOC or DPF and spend 2k+....... I might as well trade this thing in. I'd delete, but I live in Texas and just last month I had to convince the inspection place that the cat that was on my TA was actually enough for the car per EPA standards. Pretty sure a visual inspection of my truck deleted will go over just as bad. Plus, even deleting it all costs over 2k so bent over both ways. :(
 

LHN...We ARE the Joneses
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Fill out your signature so we know what you're driving.

Not that it helps with your problem, but Tx doesn't require fart sniffer testing for State inspections on Diesel.
 

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Discussion Starter #3
forgot about that. Updated. 2013 Sierra LML, completely stock. I live in the Austin area as well. I know they don't sniff, but after the fight I had to have with the inspection place for my Trans Am on longtube headers after their visual inspection... not sure I want the drama.


Last year I was in and out of there, this year they were under my car with mirrors, even gave me grief on my tires trying to say they were almost bald yet they are new tires and well within spec from the manufacturer and DOT regulations. He said they were cracking down on them, so everyone that was outside of stock was getting the full rundown. They were actually lecturing a guy with a deleted F250 when I was leaving. I'd find a more friendly shop to get it done at, but something worries me that they'll all be like this after a while.
 

LHN...We ARE the Joneses
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I'd keep the DOC and the muffler, if you altered the exhaust. DOC sweetens the smell, muff....well, I like quietness running 75-80 for hours on end....not that I'm advocating a delete.

Several years ago, the normal shop I had been swingin' by for years, were all backed up. So, I went across the street to an exclusive Inspect only shop.
Not knowing the personnel, when the guy came out to go test the brakes, I kind of jokingly said, "careful, that throttle's a bit touchy!"

Didn't like the look I got. After the stop check, he pulls into the bay for the rest of the inspect. Last thing he did was to walk down the pass side with a large Border Patrol style mirror on a stick, viewing the underside from end to end.

I asked, "what are ya lookin' for?" (exhaust is original)
Lying prick said he was checking the exhaust mounts for wear....
You can't see the rubbers' conditions with a mirror on the bottom side.
I haven't been back....hate being lied to.

On the other end of the scale, the place I happened upon out on the road, back a few months ago for an inspect.....saw it was a Diesel and never even touched the truck on their way to the PC.
 

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Man to be honest some of these trucks are just headaches with emissions. Once they start acting up it seems all the other parts follow suit. Try a different dealer, or a performance shop. Some are better than others with troubleshooting emission issues. I know you said you didn't want to delete but I'd find a new shop and talk to the owner. Basic delete could be done with a 60 dollar delete pipe and 6 to 800 for tuning. Even cheaper if you have access to a v2. The egr and all that can stay intact. Ran mine like that for thousands of miles with no issue. Good luck hope you get it worked out.
 

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Discussion Starter #6
Thanks guys. I LOVE this truck, just not the emissions systems or laws to keep it there on top of the fact that they make the replacement parts for it so damn expensive so you literally have no choice to either pay it, delete it, or sell it. If I did delete it would still have the cat, a muffler and EGR. I hate smelling like the car I just drove, which is why my TA is tuned as it is and still runs a cat.

I think I have it narrowed down to that DEF injector. Found a post here saying you can add 5V and check the spray pattern and clean it. I'll wait for the dealer to look at the tank level sensor before I pull it out for testing, but if it is clogged thankfully I can get it at Rock Auto for under $150. I just don't want to be chasing 800 bucks in sensors, injectors and parts just to find out it was the DOC and I could have just deleted. Guy in my neighborhood has a deleted F250, need to find out where he gets it inspected because it sounds like a jet airplane so it definitely doesn't pass the "sounds stock" test lol.
 

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Discussion Starter #7
Truck is at the dealer now. FINGERS CROSSED. Explained the situation to the service rep and once I mentioned the cat, he asked if I had P0420 as the code. Said it would be a few hours so they can drop the DEF tank and check the level sensor.

Looking at the datalogs last night and this morning, I noticed a couple things.

1 - Catalyst temp B1S2 shows 1832 even cold... no matter what. EGR 1,2,3,4 all read fine.
2 - DEF Injector has failed tests for all pressure related functions
3 - NOX sensors seem to be reading proper levels
4 - DEF Injector inhibit shows REGEN ACTIVE as the reason, but regen shows INACTIVE. I can see the HC1 dutycycle going up to 50% and the DEF injector pulses 1-30% (assuming by design) as I drive.
 

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Discussion Starter #8
Just as a what if, I also have their appraiser looking over the truck to have another option just in case it is a massive fix I don't want to deal with. I'm mechanically inclined, but this is my first diesel and this emissions system seems like a can of worms. Insult to injury, just got my TX registration renewal letter so I have until June to fix this.
 

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If you just have to pass a visual inspection then do the delete and hollow out your factory dpf. Tuning will eliminate the sensor issues and the need for def altogether. If you hollow your dpf yourself, the only cost would be for tuning. You could get an optimized stock ppei tune for $750
 

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Discussion Starter #10
Well they just called......

9th injector is bad
Cat needs to be replaced
DEF Module failed? (I can't even find this part anywhere)

Said they are waiting for GM to call back to see if the DEF tank is covered (at 122k but they did the heater assembly at 119, and it hasn't worked right since). I'm not convinced the cat needs the be replaced if the injector failed, maybe it isn't getting hot enough without the extra fuel? Sure as heck not paying 2k for a damn catalyst.
 

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I deleted and live in Austin - because I worry about visual inspections, my truck appears to be factory. The DPF is gutted and the DOC is still in place which cuts down on fumes and noise. It sound more or less stock - maybe ever so slightly louder - unless I'm at WOT. I also did a CP3 conversion but left the EGR in place. DEF tank is still there too.
 

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Discussion Starter #12
Thanks! Have they ever looked under?? I'd prefer not to gut if it is working, just in case and I am not afraid to just swap exhausts from the cat back each year either if I need to.


I called the dealer to clarify, the module they say is bad is the level sensor.... which was fine until they touched it to do the heater. Hence the delay. I also noticed the High pressure tests for the DEF injector failing, and those were not there before I took the truck in either. Regardless, what gets me are the lack of codes other than the P0420..... if the HC1 injector, or EGT or other sensors failed, why no warning??


I've done a rundown:

Indirect Injector $154 (PRAY that the cat isn't bad)
Level Sensor $65
DEF Injector $130

If the cat is bad, magnaflow has a diesel cat for $450 and any other sensors that I might find like EGT (40 each), NOX (150 Each)

So puts me anywhere from $350 to $1300

If the cat is bad, when I delete I have to replace that anyways.... so Already $450 in the hole there. Tune $700 on sale. Exhaust with muffler $400, EGR Blockoff $45 - $1200-1700 and needing to find a lazy inspector once a year.
 

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Discussion Starter #13
Update:

Level sensor was fine, they filled, reset it, drained it and it said empty. Refilled and it is 100% again.... whewwwww. They want $750 for the Indirect injector and a regen+labor. So I am paying my diagnostic fee and picking it up in a few.
 

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Not sure if they ever look under - they couldn't tell if they did. I bought a used one off of Craigslist (made a wanted post and had one within a day or two) for $150 I think. My original is in the corner of my garage.
 

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Discussion Starter #15
Thanks, that was the route I was heading once I knew this thing was going to be too much. Now with these smaller sensors


Picked up, drove it on the highway with my scanner, cleared the code for Catalyst and it started a regen. 10min and it went to 14g of soot and marked it complete. Catalyst Temp B1S2 still pegged at 1832deg which is weird because EGT B1S2 shows normal???? I thought that they were the same, but can someone confirm? The Def Injector fails all pressure tests, so that could be why it takes longer to finish a regen.
 

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Discussion Starter #16
Just took it for a trip to lunch. Code shows in history, but didn't trigger a CEL yet. My scanner shows 1 warmup without a code completed and the readiness of the NMHC cat is incomplete, so just have to drive it around according to what I have read. Could take up to 5 warmup cycles to finish those tests.
 

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Discussion Starter #18
Makes sense. I still see the DEF injector firing once the truck is on the highway and after reading more it seems that is there to convert it to nitrogen and water. So it still could be that 9th Injector? Cat lights off and all the EGT's seem normal as well, up over 650-700 before and 1000* through all the others until the regen stops and they all drop back to around 550*. I'll have to see once the soot climbs enough for the next regen, but right now, everything seems to be functioning again, thankfully.
 

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I'd keep the DOC and the muffler, if you altered the exhaust. DOC sweetens the smell, muff....well, I like quietness running 75-80 for hours on end....not that I'm advocating a delete.

Several years ago, the normal shop I had been swingin' by for years, were all backed up. So, I went across the street to an exclusive Inspect only shop.
Not knowing the personnel, when the guy came out to go test the brakes, I kind of jokingly said, "careful, that throttle's a bit touchy!"

Didn't like the look I got. After the stop check, he pulls into the bay for the rest of the inspect. Last thing he did was to walk down the pass side with a large Border Patrol style mirror on a stick, viewing the underside from end to end.

I asked, "what are ya lookin' for?" (exhaust is original)
Lying prick said he was checking the exhaust mounts for wear....
You can't see the rubbers' conditions with a mirror on the bottom side.
I haven't been back....hate being lied to.

On the other end of the scale, the place I happened upon out on the road, back a few months ago for an inspect.....saw it was a Diesel and never even touched the truck on their way to the PC.


back before we got rid of emissions testing all together (gas and diesel) used to be that they only IM tested gas. So to register you would literally take your truck to jiffy lube or wherever and the guy would stick his head out the window, listen to the truck to make sure you didnt spend several thousand dolars to replace the diesel with a gas engine to save on the IM testing fee (because apparently people were doing that?) and would hand you your exempt sticker to take to DMV. Now they just dont care at all what you roll down the road and they just charge you a fee at DMV.

As for the OP's issue. I would just do a stealth delete on the truck. leave the stock exhaust on it, leave the DEF tank and be done with all of that nonsense.
 

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A few comments and thoughts to share. I monitor regens on my Torque app, so my parameters are not a direct comparison to yours I suspect.

When in regen mode, when the 9th injector is active, you should see a large temperature rise from EGTB1S1 to EGTB1S2. This is the hydrocarbons/diesel fuel oxidizing across the DOC to produce the heat needed to remove the ash and particulate matter from your DPF. Normal EGTB1S1 temps while in regen range from 550 - 700F during driving, EGTB1S2 temps will be in the 1000 - 1300F (this is post DOC). From experience, it seems that EGTB1S3 and EGTB1S4 need to achieve about 1100 - 1150 F for 5 - 10 minutes, at the end of a successful regen.

On the DEF side, I'm not able to monitor DEF dosing or NOx values with the Torque app, but you should see the DEF injector start dosing when EGTB1S2 and EGTB1S3 are reading about 400F or above. When the exhaust is warm enough and the DEF injector is active, you should see DIFFERENT NOx sensor values, which suggest that the DEF is being injected and reducing the NOx that comes out of the engine and goes through the SCR catalyst.

Hope this helps...
 
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