P0300 and flashing check engine light


Asked by Tkelce58 Feb 18, 2017 at 08:34 PM about the 2005 Chevrolet Colorado Z71 Extended Cab RWD

Question type: Maintenance & Repair

Hi my colorado check engine light is flashing and
showing the P0300 code. I've changed my plugs
tested my coils cleaned my map and maf sensor.
Replaced my crankshaft sensor and air filter and
cleaned my throttle body.  And it is idling a lil rough
and lights are still the same. And i checked for
vacuum leaks.I need help! It is the 5cyl 3500

14 Answers


Possible causes; Faulty spark plug (s), Faulty ignition coil (s), Clogged or faulty fuel injector (s), Intake air leak, Fuel injectors harness is open or shorted, Fuel Injectors circuit poor electrical connection, Ignition coils harness is open or shorted, Ignition coils circuit poor electrical connection, Insufficient cylinders compression, Incorrect fuel pressure...The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem.

16 people found this helpful.

Ok I had a diagnostic done on it today.The #1 cylinder has a slight miss and the #4 has a bad miss. Do compression checks on both and their good. Replaced the coils and checked for air leaks and nothing. And it's still missfiring. Any ideas

5 people found this helpful.

Read my possible causes.

6 people found this helpful.

My mechanic told me to ohm out the coil wires. But I would think that there's a small chance of that since cylinder 1 and 4 are missfiring correct?

2 people found this helpful.

Well, you have checked pretty much the major things that cause a miss, and are not coming up with anything. In testing spark plug wires you do this with a digital multi meter set on the ohms Ω setting. Have a lead on each end, the resistance is 8000Ω per foot indicating a good wire. Also have you gone threw and snugged up the intake manifold bolts, check the throttle body screws and base bolts, just go threw an make sure there snug. No over tightening.

8 people found this helpful.

Ok the mechanic told me I have 2 bad injectors. Do you have any how to videos or any information on how to replace the injectors. And do I have to remove the resonator box to get access to these. And would it be a bad idea to buy a refurbished injector instead of a new one. Because there's a pretty big price difference. Thanks for all your help

5 people found this helpful.

I have no preference on using a refurbished injector or not, and there is all kinds of video on you tube on how to change a fuel injector.

7 people found this helpful.

Good luck with that.If you check out the internet you will find the 2.8 and the 3.5 engines are a nightmare for throwing codes like lean mixture,multiple misfires, etc. Most are from bad heads on earlier engines. Stupid design on intake manifold for pvc hose internally where you can't service it. Outrages costs to fix. I will never ever by another Chevrolet again. I bought many new Chevy trucks in the past for business and I will now go with a Toyota.

5 people found this helpful.

I agree , my 06 Colorado 3.5l just started doing the same. I replaced the coil and the spark plug. I heard something about a recall on this issue, saying that have to rebuild the head. Anyone else know anything about this issue.

8 people found this helpful.

How do you clean the fuel injector on a 2006 Chevy Colorado

3 people found this helpful.

Ok , this is pretty related except I spent all of about $182.00, I was having a lot of issues W/my 2004 Chevy Colorado z71 3.5 /5 cylinder vortex 3500 engine reduced dummie light coming on . The 1st time it happened was in August of 2018,I thought it was a glitch/short ? Pulled over called a friend an well smacked the thottle control a couple whacks w/ a rubber mallet, good to go never looking back on it till 2019 around January.... well same processe ,pretty much inn the let's wasn't as effective... Around the middle of feburary boy oh boy ... problem was so bad a little hill was almost unconquerable... not working due to a injury fresh surgery I was unable to bye part's . Butttttttt thanks to family/friends, light came. Threw the tunnel except for one thing ,w/ a change out on sensors like mass air flow, map sensor, and my throttle body, still the loss of power w/ power reduced dummie light an a hill my grandma could walk up faster then my truck was still. Well let's say being a punch inn the gut... an this was making grown men w/ schooling experience scratching a bald spot on their head in one area from not understanding what the heck was the issue,it would show codes from missing ,cam Sensor A extra, on an on!!!!!!! WELL LET'S JUST SAY THAT there was a pop up along the line about the cylinder missing but also back pressure was making a lot of codes going off, finally an getting to the point my catalytic converter was the issue ,plugged up so bad that all the codes we thought it was an possibly could have been an the one we fixed due to this issue in which was a 2 slice an it was out of there a pipe put back on an end story oh by the way, its April now. 2019 just saying don't always go buy a part researching did take a lot of time an really still to this day I don't know what made me think to cut it off other then to see honestly if there would be a difference of some sort so thank you for your time an I hope this saves all of you some graying and bald areas on your head's from a no cost an more time putting miles on your truck is/cars an time well spent w/friends an family's

2 people found this helpful.



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2 people found this helpful.

Anyone have any luck with the P0301 code? Changed plugs, coil pack and injector lasted about 6 months then came the check engine light again been driving a year since then runs fine mainly comes on when I let it idle in park for a while with the AC or heat on then goes away in 3 or so days, think I'm going to check for a vacuum leak now may just be a bad sensor, dealership I bought it from said my vin number wasn't on the recall list it was a local trade in with less than a 100,000 on it 2006 crew cab 4x4 nice truck cheaply made thin metal, not enough cup holders, air gets in the door seals around 70 miles an hour, I liked the old 6 cylinder had a 2000 Jimmy with one good motor and the transfer case says Isuzu at least they could have slapped a Chevy sticker on it.

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