Metal particulate in fuel- P026D troubleshooting

My issue involves '17 L5P with ~120K. I've seen on several DMax forums a concern with metal particulate in the fuel. I'm getting a P026D (and occasionally a P2A00) DTCs. One of the troubleshooting steps included an inspection/flushing of the fuel system lines. Yes, I found some metal particulate in my filter bowl, but how many are actually getting past the filter remains a question. (I haven't flushed my lines, but have changed the fuel filter recently.) My injector balance rates appear normal: 0 +/- 0.5 variation with an occasional spike on one or two injectors, upwards of 1 to -1, then reverting back to something closer to 0.5/-0.5 (this, in either Park or in gear). Fuel consumption hasn't changed noticeably, there's no hesitation on acceleration and it idles smoothly. So, what can be generally expected on a fuel system and will the stock filter (Delco TP1015) be sufficient?

As to the DTC codes, they appear intermittently with the P026D the one most prominent, and of lesser occurrence the P2A00. The CEL may or may not illuminate. The error conditions are not "hard"- meaning, I can clear them and drive some 300 miles on a highway trip, with a couple of stops, and not incur an error. I'm thinking I have an intermittent electrical issue, perhaps corrosion judging from some of the TSBs I've found. I've changed the air filter, fuel filter, cleaned the MAF and MAP sensors. A TSB suggests corrosion on the fuel pressure sensor connector (which sits behind the CAC return pipe- just below the Throttle Body assembly). And, the only other issue may be what appears to be a slight disengagement of the connection at the discharge port of the inter-cooler itself (it doesn't look as if the return pipe connection is fully seated at the discharge end).

Looking for ideas before resigning myself to the dealership. Any of you tech experts have any thoughts or tips? Thanks!

The metal particles are likely coming from the fuel station(s) you're using. Years ago I visited a local station that had just been built before I left town on a trip. It was convenient and I didn't know any better. By the time I had traveled 200 miles, the truck would barely run, very difficult to start and had a noticeable loss in power. The problem was because of plugged fuel filters. I had just changed them before the trip, but that brand new fuel station must have had a ton of manufacturing debris in the tanks/lines. Lesson here: Only buy fuel from established and well trafficked higher volume fuel stations - preferably those that filter the fuel before it reaches your pump.

Otherwise, the filter should be catching whatever might a problem. The designers of these fuel systems know we live in the real world. You may need to increase the frequency of filter R&R (or add a second) if you can't get away from the contaminated fuel. Some station near you has good clean fuel.

P026D - From what I can find out, you should consider: 1- Try running with a loosened fuel tank cap to eliminate a bad cap vent. A diesel fuel tank cap is supposed to vent at 2-psi positive pressure or 1" vacuum. Too much +/- can do unwanted things to a diesel fuel system including engine running problems. 2- Clean the MAF sensor. 3- DPF regen cycles are best done on the highway at highway speeds. One fellow reported that after about 5 highway regens, the P026D had completely gone away.

Thanks for the response MP-
I"m attempting to resolve this 026D step by step. MAF was cleaned and even replaced at one point- no change. I noted the harness pigtail at the MAF positioned about 20+ degrees down from "in line" with the sensor; the back end of that connector feeling "loose". (I made contact with it once when refilling the DEF- slipped and after contact noted something from the bottom of the connector fall off). It seemed the harness placed too much strain on that connection, so I removed the harness mount from the air box, repositioned the harness and secured it. Cleared the codes and ran the **** out of her- enough to reset my emissions flags. After 263+ "warm ups w/o an emissions malfunction" and no other codes, a jarring pothole induced my first 026D in quite a while- so, I'm thinking I may have a connector issue at the MAF.

I'll run with the fuel cap a bit loose for a while and see what happens. I'll also give her some highway time when the next few regens start up. Balance rates look good (+/-1.0 or less) so I'm not considering an injector issue. I've got just about everything else addressed that I was able to find. A rare P2A00 may come up in addition to the 026D, but it's one thing at a time for a while.

Thanks for the insight.

It could also be that the CP4 pump is beginning to fail. The return fuel will carry the metal to the tank. The CP4s are known to eat themselves because of poor fuel filtration allowing contaminates to go into the entire fuel system. It has been explained to me that the clearances within the CP4 are very close so any contaminate could conceivably destroy the pump. The worse part is that everything in the system has got to be changed out at great expense. Hope that you can avoid this with finding something like More Power has said as a bad fuel load. The fuel filter should not be allowed to go beyond 50% on the DIC in my opinion.

Me being new to the L5P stuff, I did some more research and found that the LML engines had the CP4 pumps that destroyed themselves. The seventeen and up have been repumped to the Denso HP4 which is much more reliable. Gm has gotten away from Bosch completely it seems at least in the diesel trucks.

For many many years now I have been running and promoting the use of a Filtermag on the OE fuel and oil filters. Not much you can do in the L5P since it's not a can type though.

Ill be doing frequent filter changes.