2014 Sierra P0300 CEL flashing with TC light

B14Sierra · July 10, 2019

So as the title states. 2014 Sietra 6.2l with flashing CEL and TC light on. 94,000 miles. I had this problem before and it turned out a broken valve spring but I had a ticking noise. I could tell last time sonething happened because the truck skipped in was noticiable something happened. This time didn't notice anything except the lights. At 70 mph everything seemed ok. Pulled over it didn't start right away and had a bad miss. Got it home only a few miles and checked all the wires. Seemed ok. Took my other truck into town and changed all the plugs and wires still acting up. Plugs looked all golden brown and not wet. For the hell of it pulled both valve covers and ran it. Everything seems fine. Checked each rocker nothing loose. Had my friend loan me a cheap code reader. P0300 and I have had the cylinder five P0305 but it doesn't come up constant. Sometimes it does sonetimes it's not there. Had the rough cold idle one too but again it's not constent. I'm leaning towards injector or injectors. It's weird because if I let it sut overnight when I start it, it seems to feel like one cylinder but the longer it runs it gets way worse feeling like multiple cylinders. Also it runs better at higher rpms with a slight miss at times. Any ideas besides injector or injectors?

B14Sierra · July 10, 2019

Also, I swapped cylinder 5 coil pack with a different cylinder and still ended up with a cylinder 5 miss.

Lsgun1 · July 10, 2019

Sounds like you did a good basic diagnosis. I'd check compression on that cylinder before throwing an injector at it.

jay webb · August 18, 2019

if the compression test dont show anything on #5 then most likely injectors

or carbon build up on valves. if not both.

if you chose to take it to dealership they can preform an injector balance test and determine what injector(s) are the cause.

typically for just a diag fee which is usually 1 hr of shop rate.

if it is injectors its the typical quote is about 5 hrs with the diag + injector(s) + seal kit + high pressure fuel lines ( 2) the run from the high pressure fuel pump under the intake to the fuel rails. typical out of pocket on an injector repair is $1000-$1500 depending on how many injectors.

the 6.2 engines can have 1 of 3 different injectors cant know til they are pulled. the reason being is for engine balance, so they are flow tested and installed at the factory this way. you have to see the part # on the injector.