P050D with a random P300

jenglish421 · January 11, 2021

So I have a 2017 GMC Sierra 1500 with the 5.3 at 35k miles and I got a flashing CEL for about 30 seconds a few weeks ago on the highway and took it it to auto parts store but it had no codes present. About a week and a half ago the CEL came on constant and it came up with the P50D Rough Idle and so I got oil changed and ran some fuel system cleaner through and after a couple days the light started flashing and ran rough for a few min, I parked it and started it 10 min later and it was a solid CEL again but I was able to pull a P300 General misfire code. Today it did the same thing but ran worse than ever and I thought it was going to die on me, shut it down for 10 min and it ran ok. Before I start throwing money at this where should I start, spark plugs, coil packs, injectors? I'm at a loss with only 35k and just passed the 3yr warranty. Thanks for any advice.

silveradosid · January 12, 2021

need a better scan done, need to see the freeze frame data of when the cel was triggered. your symptoms point to an injector problem, but you need to have a full scan done first

jenglish421 · January 12, 2021

I appreciate the response, do you have any recommendations for a scanning tool to do this? I am planning to schedule with a local mechanic that I trust today but if its something that I can get and have for future issues and its cheap and worth it. Thanks again.

silveradosid · January 13, 2021

vcx nano for gm is the cheapest way to go. it is sometimes a pain in the a%% to get it to connect , but works really well. i use mine a lot

jenglish421 · January 13, 2021

Thank you again, I will look into this one

newdude · January 13, 2021

On 1/11/2021 at 2:26 PM, jenglish421 said:

So I have a 2017 GMC Sierra 1500 with the 5.3 at 35k miles and I got a flashing CEL for about 30 seconds a few weeks ago on the highway and took it it to auto parts store but it had no codes present. About a week and a half ago the CEL came on constant and it came up with the P50D Rough Idle and so I got oil changed and ran some fuel system cleaner through and after a couple days the light started flashing and ran rough for a few min, I parked it and started it 10 min later and it was a solid CEL again but I was able to pull a P300 General misfire code. Today it did the same thing but ran worse than ever and I thought it was going to die on me, shut it down for 10 min and it ran ok. Before I start throwing money at this where should I start, spark plugs, coil packs, injectors? I'm at a loss with only 35k and just passed the 3yr warranty. Thanks for any advice.

You still have powertrain which is 5yr/60k. Take it in.

jenglish421 · January 13, 2021

Not for injectors, 3yr/36k.

I need to troubleshoot and figure it out then go from there, if its an injector or a coil pack I can handle that myself. Symptoms match one of those and I'm leaning towards injector but I need to know for sure so I'm not wasting money

newdude · January 13, 2021

1 hour ago, jenglish421 said:

Not for injectors, 3yr/36k.

I need to troubleshoot and figure it out then go from there, if its an injector or a coil pack I can handle that myself. Symptoms match one of those and I'm leaning towards injector but I need to know for sure so I'm not wasting money

Spend the $150 and let the dealer diagnose it then. Unless you have access to GM's AFIT injector tester or a good scanner that can pull injector balance rates, you will be throwing parts at it.