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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29585
Experience:  GM Grand Master Technician 2007. 14 year experience.
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I have a 2000 yukon 5.3l, Engine light blinks when rpms are

Customer Question

I have a 2000 yukon 5.3l, Engine light blinks when rpms are higher usually on the freeway or if your slow to accelerate to speed in city traffic, light does not come on or blink unless rpms are at 1800 and up for a period of time, engine light turns itself off after driving a few times in city traffic, engine code is p0300, plugs, fuel pump, fuel lines have been replaced in the last year but light still comes on and blinks
Submitted: 2 years ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 2 years ago.

Hi there, I am Cam. I'm sorry to hear about this issue with your vehicle. The flashing check engine light indicates there is catalyst damaging event happening, usually a misfire due to plug wires, plugs, or low fuel pressure for whatever reason. It may also be that you have a plugged catalytic converter.

Customer: replied 2 years ago.
I pulled the cats off this morning, started the engine and ran it till it got to temp then throttled to 1800rpm, engine light was off to start with but it started blinking after 15 seconds at 1800rpm
Customer: replied 2 years ago.
now I dont have the o2's plugged in right now cause I pulled the cats off so would that cause a blinking engine light too and should i plug them back in and do the rpm test again?
Expert:  Gm Tech (Cam) replied 2 years ago.

Having the catalytic converter is removed and the oxygen sensors unplug will not induce the flashing check engine light, so that tells me your problem is likely related to something else. Even now with the new fuel pump, do you feel that the engine is lacking in power? Also, can you confirm that you replace the fuel filter very recently in the repairs to correct this?

Customer: replied 2 years ago.
fuel pump, filter and plugs were replaced at the same time around a year ago but it had this problem before I replaced them, it doesn't feel like its lacking in power, it still shifts quickly and will accelerate to 90+mph pretty quickly before the engine light comes on or blinks
Expert:  Gm Tech (Cam) replied 2 years ago.

OK, in the past year since you have done those repairs, has anything changed the behavior? Has it become worse in anyway?

Customer: replied 2 years ago.
it starts and runs better but the light doesn't seem to have changed much, it might take a few seconds longer for the light to come on than before
Expert:  Gm Tech (Cam) replied 2 years ago.
OK, I don't suppose you have a scanner that will allow you to see the actual misfires on each cylinder? Knowing which cylinders are misfiring certainly help. And I don't want to start throwing more parts at this issue until we have a clear direction of where the problem is.
Customer: replied 2 years ago.
I do have a scanner but I don't think it gives that much data, its an innova equus
Expert:  Gm Tech (Cam) replied 2 years ago.
It' sounds like a code reader. We will need to see that live data to find out what's wrong.
Customer: replied 2 years ago.
yeah just checked it and its just a code reader, bummer, I do appreciate your help but its looking more likely I will be taking it in for diagnosis unless I can get my hands on an actual scanner. Thanks again ***** *****
Expert:  Gm Tech (Cam) replied 2 years ago.
Your welcome Mike.
Thank you for allowing me to assist you. Please rate my answer 3-5 and feel free to ask any follow up questions regarding this issue you may have. Again if you need further information, please use the Reply/Continue Conversation link to ask for more help and I would be happy to assist you further. You do not need to give a negative rating or relist the question to get more help :)