Problems attempting injector cleaning

[garyrosa123]

Hello fellow members, and thank you for providing such an informative forum. I have a 2018 Silverado 3500LTZ 6.6 Duramax L5P, and attempted a fuel injector cleaning today. Removed every fuse and relay labeled fuel, and could not get the lift pump to stop pumping fuel, and the engine never started, just cranked. Re-assembled fuel lines, and back to square one after fuel clean-up. Reason I was going to perform a fuel injector cleaning is, 120,000 miles on it, all stock, fuel injector connector #4 went bad, I replaced it with $100 OEM connector, reset P0204 injector circuit code, and it runs good, no codes, except for slight vibration in park at approx. 1200 rpm. Same noticeable vibration at approx. 12-1,400 rpm while driving. I have read all about harmonic balancer, and flywheel could be issues, and checked them both. Am I looking at possible bad injector, clogged injector, or injector timing? Heck I dunno I'm no diesel mechanic, however can perform what is thrown at me. Ideas or suggestions for the 2018 that apparently has a lift pump that loves to run, and engine requires pressure at the lines to run?

 

[TheBac]

Moved this into its own thread in L5P.

 

[garyrosa123]

Moved this into its own thread in L5P.

No suggestions, or replies. Admin, Please delete this thread named

"Problems after injector cleaning"​

Dealing with Nox sensors. etc which are now popping up. Leaning far away from L5P as parts are not available.
Thank you,
Gary

 

[TheBac]

Thats not how things work here, so we'll leave it up.
Keep in mind, this isnt "Fixya". People answer if they know, but it can sometimes take a while.

 

[Ron Nielson]

If your fuel pump is running all the time, it has battery power and ground all the time, perhaps not the way you would expect it to have. Perhaps your fuel pump relay is stuck running, or your fuel pump driver control failed to constant run status. If you want to dig into it, download the wiring diagram from here: https://www.gmupfitter.com/wp-content/uploads/2021/05/18_Sierra_Body_Builder_2017AUG31.pdf and make sure your test light and DVOM are in good working condition.

Could it be that your truck is merely trying to fill up the fuel system after your injector cleaning?

 

[garyrosa123]

If your fuel pump is running all the time, it has battery power and ground all the time, perhaps not the way you would expect it to have. Perhaps your fuel pump relay is stuck running, or your fuel pump driver control failed to constant run status. If you want to dig into it, download the wiring diagram from here: https://www.gmupfitter.com/wp-content/uploads/2021/05/18_Sierra_Body_Builder_2017AUG31.pdf and make sure your test light and DVOM are in good working condition.

Could it be that your truck is merely trying to fill up the fuel system after your injector cleaning?

Thank you for the reply. The info you sent will definitely be useful in tracking down the source. I tried to disable the pump to do the cleaning, and it just kept running. Didn't get to perform cleaning. Yesterday the CEL came back on, and NOX codes are haunting now. New fuel filter, new stock air filter, map sensor cleaned, MAF sensor cleaned, #4 injector pigtail replaced which was the original issue (P0204), now getting P20EE code. Taking it to a local shop today to run diags to see what's up. Just hasn't been right, and has a vibration around 1200 -1400RPM in park/neutral, now NOX issues. I appreciate your input, and will update as I progress.

 

[juddski88]

The NOx module comm issue is, unfortunately, fairly common on the l5p. They were on backorder for several months, and may still be.

 

[garyrosa123]

The NOx module comm issue is, unfortunately, fairly common on the l5p. They were on backorder for several months, and may still be.

Upstream is on national backorder, and I have a downstream coming one day next week, needed or not. I've been reading, and DEF injector can also be related to NOX. Hopefully local shop can shine light.

 

[juddski88]

The DEF injector, among many abnormal operating conditions, can mess up a sensor or cause readings to be out of range, but it won't kill the module communication

 

[garyrosa123]

Well, Shop scheduled an appointment for next week. Said they have another truck, 2018 as well, awaiting NOX sensor on natl. back order. I'm thinking go with aftermarket and have one in hand when I take the truck in for appointment. Any suggestions on aftermarket for oem #s NOX 12680215 superseded 12718742. This is NOX position 1, and I found NOX 2, will be here next week, needed or not.

 

[garyrosa123]

Follow-up.. Truck spent two days in the shop and is now purring as it should. I have yet to clean injectors, however thought I would update. I replaced NOX position 1 and 2 once I found OEM of each. Shop flashed ecm, and informed me there was a huge list of updates my ecm had never received. Once ecm was flashed they did a relearn and sync on everything related, and walaa running like a champ. I've run hot shot diesel secrets injector cleaner through a full tank per dosing, and will wait on cleaning injectors. So far so good, and heading out soon on a cross country trip. Will see how she performs. Once NOX and ecm program $800 later all is well.
Wishing everyone the best. As for now, running like a champ
Gary

 

[Ron Nielson]

Great that you got the truck fixed. Seems like more and more people can't figure out what to fix, or parts and are just not available.

 

[garyrosa123]

Great that you got the truck fixed. Seems like more and more people can't figure out what to fix, or parts and are just not available.

In my case unavailable parts made it difficult to resolve. Ordering extra sensors to have on hand. I have a few OBD2 readers to clear codes etc. and looking to purchase reader/writer for the future.