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I was looking all over in there with a flash light, even took the intake hose off, I must have missed it. But I'll take your word for it about being a PIA.

CRC has a spray cleaner just for electrical connectors. I used it before on the main airbag plug in my 98 Dodge and it worked fine.

Thanks!
The bulletin says it may be burnt.....rewire kit about $35. Last resort here.

Update to follow
I've cleared my P026D code several times, and it comes back on at each and every start up. Do you guys think this is covered under the factory warranty? I bought mine used with no warranty, and it has about 66k miles on it now.
I'm told no, not even 5/ 100. This is the latest in a long list of CELs for me. I hope it's just dirt and trash and not burnt.

Ironic, GM is offering me 6 / 60 more for $4700 ez finance zero deduct. I'm thinking my claims could wear this offer smooth out with CEL and injector issues. They would def go negative on my deal. Just have a problem paying them to fix their engineering mistakes.
 

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So I have a 2017 Silverado 2500HD and I had a service engine light come on. Took it to a shop and was told the rail pressure was way to high so they replaced the fuel pump. Two days later I am hauling and use the Exhaust Brake and the service light comes on. I get home from hauling and have the code checked and it is the P026D code. The shop pulled the #2 injector and said it was fine a bit sooty but fine. I have 118,000 on the truck. I have seen a lot of different items suggested for this code. Any help would be greatly appreciated.
 

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If anyone has been able to get to the fuel pressure sensor connector to inspect it, please post up what you did and what you found.

Thanks-

BTW- Since this code came back for me, it went away on its own and has not come back. I since installed a Banks iDash and from what I can tell on the iDash, the truck is running fine. If I can put it off until winter, I will work my way into the sensor then and post it up.
 

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OK, so I may finally be getting somewhere with my P026D. Keep in mind that about a year ago my truck had P026D semi-solved by removing the fuel filter and flushing the system. At that time they found the brass type metal bits in the fuel filter. So, now, my fuel filter is starting to get clogged, about 75% life, and the code comes back. I take it in and they find more brass bits in the filter. But this time, they have more experience with the problem and suspect the in-tank pump. Apparently it was failing and that was the cause. Only time will tell, but here is the tech's comments below...

"Checked fuel filter and found excessive brass in filter from internal fuel pump failure. Found excessive brass material in filter housing coming from in-tank fuel pump bushing coming apart. Replace in-tank fuel pump. Did not see material in tank. Flush fuel lines, flush fuel filter housing, install new fuel filter, clear codes, road test vehicle, no codes reset during road test."

Well only time will tell about that. But I guess since there was no "material in tank" then they ruled out the high pressure pump failing and sending metal back through the return line. I know GMC went to the Denso high pressure pump because the last pump had a lot of problems. If my truck goes back in the shop for this code, I will be pushing for the high pressure pump to be replaced.

BTW- I've replaced a few of these in-tank pumps in my day, the best idea is to run the truck almost dry of gas. And you need a strap wrench to get the pump out.

I hope this helps someone-
 

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OK, so I may finally be getting somewhere with my P026D. Keep in mind that about a year ago my truck had P026D semi-solved by removing the fuel filter and flushing the system. At that time they found the brass type metal bits in the fuel filter. So, now, my fuel filter is starting to get clogged, about 75% life, and the code comes back. I take it in and they find more brass bits in the filter. But this time, they have more experience with the problem and suspect the in-tank pump. Apparently it was failing and that was the cause. Only time will tell, but here is the tech's comments below...

"Checked fuel filter and found excessive brass in filter from internal fuel pump failure. Found excessive brass material in filter housing coming from in-tank fuel pump bushing coming apart. Replace in-tank fuel pump. Did not see material in tank. Flush fuel lines, flush fuel filter housing, install new fuel filter, clear codes, road test vehicle, no codes reset during road test."

Well only time will tell about that. But I guess since there was no "material in tank" then they ruled out the high pressure pump failing and sending metal back through the return line. I know GMC went to the Denso high pressure pump because the last pump had a lot of problems. If my truck goes back in the shop for this code, I will be pushing for the high pressure pump to be replaced.

BTW- I've replaced a few of these in-tank pumps in my day, the best idea is to run the truck almost dry of gas. And you need a strap wrench to get the pump out.

I hope this helps someone-
Well hate to burst your bubble but I had the code come on, replace the high pressure pump and had it all flushed out and it was fine for about 2 months and the light is back on with the same code. Not sure what it could be this time. I have already replaced all of the glow plugs and had the injectors looked at as well. Next will be a sensor that I hear is supposed to the cause because it gets all sooty or a collapsed fuel tank. I doubt the tank is the issue since I can fill it and the pump works etc... I am almost to the point where F**K it the truck works and I still get great MPG so the light stays on.
 

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If I understand your post, changing the high pressure pump did not solve P026D on your truck.

So maybe it is the in-tank pump🤞
 

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OK, so my code came back after the fuel flush, filter change, in-tank pump replacement. I dug into this code to find out that the code is triggered by low oxygen (O2) readings by NOX sensor 1 (under the hood, driver's side, just in front of instrument cluster). The NOX sensor measures both O2 and NOX. I started to monitor the NOX-1 sensor on my Banks iDash and saw that that is was taking a long time to turn on and then the readings were highly variable. The dealership tested it and found it was taking up to 20 minutes to turn on. They said it has an internal heater that was "open" and not turning on. It was replaced under the emissions warranty. This was the first thing they replaced when this problem started a year ago. It seems the replacement NOX-1 was faulty from the start.

If you have this code and a Banks iDash or somethig similar, set it up to show NOX-1 output. Per GM spec, the sensor should give output within a minute or two of start up. Also, it seems the readings were all over the place before, but now they are much more stable. I will monitor it on my next drive and report back.

Fingers-crossed this is the real solution-
 

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OK, so my code came back after the fuel flush, filter change, in-tank pump replacement. I dug into this code to find out that the code is triggered by low oxygen (O2) readings by NOX sensor 1 (under the hood, driver's side, just in front of instrument cluster). The NOX sensor measures both O2 and NOX. I started to monitor the NOX-1 sensor on my Banks iDash and saw that that is was taking a long time to turn on and then the readings were highly variable. The dealership tested it and found it was taking up to 20 minutes to turn on. They said it has an internal heater that was "open" and not turning on. It was replaced under the emissions warranty. This was the first thing they replaced when this problem started a year ago. It seems the replacement NOX-1 was faulty from the start.

If you have this code and a Banks iDash or somethig similar, set it up to show NOX-1 output. Per GM spec, the sensor should give output within a minute or two of start up. Also, it seems the readings were all over the place before, but now they are much more stable. I will monitor it on my next drive and report back.

Fingers-crossed this is the real solution-
Waiting patiently........
 

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I've driven about 15 trips over the weekend and no code. The code was popping everytime before this fix. This seems to have "woke" the truck up. It is more peppy with the throttle now. MPG on the DIC is up also. I will post back up after my next fillup to compare direct measured mpg before and after. NOX-1 readings on the idash are not as jumpy and are stable at idle, they do vary when driving.

I try to be an optimist, so I think this is it. The longer it goes, the better.

This sensor is easy to change yourself, but there is a trick, I think it needs to be calibrated after installation. That takes a fairly expensive code reader
 

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I talked to GM tech. The P026d whoops their ass, total nuisance code. He said TMAP, NOX-1, Def injector, fuel injector can all call for it plus the fuel rail sensor, which I did. Still have code.

Since my Tmap and fuel sensors are good, ill wait for you to report back on NOX 1 before I drop $170 on that.
 

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Just to be clear they replaced my NOX-1 last week and it seems to have solved the problem. But I will let you know if the code comes back.

They did some kind of test on my NOX-1 and saw an open circuit for the sensor's built in heater. I guess that means the heater burned out. Maybe you could find the instructions for testing if the heater on your NOX-1 is burned out or failing? Maybe it takes a fancy code reader, I don't know-
 

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Yeah, likely Autel or tech 2. Autel is around $2400, the sensor is $167 lol.

I can reset the light a few more times while you drive around a bit...
 

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If we could figure out the pin assignments for the NOX-1 wiring harness, you could probably just test for continuity (with a normal multi-meter) across the +/- of the sensor heater. Then if you saw no continuity, that would show that the heater is burned out?

Otherwise, I post back if the code comes on again.
 

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If we could figure out the pin assignments for the NOX-1 wiring harness, you could probably just test for continuity (with a normal multi-meter) across the +/- of the sensor heater. Then if you saw no continuity, that would show that the heater is burned out?

Otherwise, I post back if the code comes on again.
How many miles since Nox 1 change out ?
 

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Funny you should ask, yesterday my mpg started to drop (not in regen), then next key cycle P026D and today the NOX 1 was taking ~5 minutes to turn on (should be <2 per GM specs). So either my truck blows NOX-1 sensors or my dealership got a lot of bum NOX-1 sensors. It will be back in the shop on Tuesday.

I feel certain that my P026D is caused by the blown NOX-1 after what happened today. Apparently, poor MPG is a symptom of a bad NOX-1. When the computer can't get data from NOX-1 it assumes a worst case scenario and runs rich (too much fuel), so your mpg suffers.
 

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Funny you should ask, yesterday my mpg started to drop (not in regen), then next key cycle P026D and today the NOX 1 was taking ~5 minutes to turn on (should be <2 per GM specs). So either my truck blows NOX-1 sensors or my dealership got a lot of bum NOX-1 sensors. It will be back in the shop on Tuesday.

I feel certain that my P026D is caused by the blown NOX-1 after what happened today. Apparently, poor MPG is a symptom of a bad NOX-1. When the computer can't get data from NOX-1 it assumes a worst case scenario and runs rich (too much fuel), so your mpg suffers.
Interesting, what is " bad mpg's" ? Like 14 hwy at 65? That's what I see in regen otherwise 19-20
 

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When I sad bad mpg, I meant it in a relative way, whatever you get with a good NOX-1 you will get worse with a bad NOX-1. This seems to be a general pattern for all diesels, based on the way the computer uses the NOX-1 data to optimize the fuel economy.

With the bad NOX-1, my DIC was saying 17.2mpg, but the real mpg was 16.5 with one regen between fill ups. With the good NOX-1 sensor, the DIC was saying 18.9, but I did not get to do a direct measure before the new NOX-1 went bad, I had only driven about 200 miles.
 

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My truck was in the shop for a couple days and they called to come get it..... their only diesel tech is scheduled on vacation until next week. lol He did not make much progress in two days, but they say he is focusing on the EGR valve (front egr valve I think).

If you look at both GM and Volvos diagnostic work flows for this code it does lead to an EGR valve sticking open or closed. What a world we live in-
 
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