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Old 09-14-2017, 08:25 PM   #1
bikernut
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flashing check engine light

I have a flashing check engine light that flashes when I get between 2100-2500 rpm on my 2003,3500 with 6.0 engine. it will not set a code, it flashes for a bit and stops. It doesn't matter if I am hauling my small tractor, plowing snow or just steady driving. I have replaced the knock sensors with GM factory replacements to see if that was the problem but no. hoping some one has had the same thing happen and can send me in the right direction.
thanks
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Old 09-14-2017, 09:22 PM   #2
greasemonkey
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Re: flashing check engine light

Our mill truck did that, and also idled and accelerated poorly. I understand that a blinking engine light is a misfire. What is the condition of your ignition system? Basics like plugs/wires? A simple tune up fixed ours.
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Old 09-15-2017, 04:12 AM   #3
bikernut
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Re: flashing check engine light

had these items checked and every thing seems to be okay
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Old 09-15-2017, 08:22 AM   #4
homemade87
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Re: flashing check engine light

Gm set the mill light to flash when things need immediate attention . Like a dead cylinder . Not just a miss fire . There are other codes for that and if the mill light is steady on there is a problem and needs to be looked at soon but not urgent .

My 06 did this and turned out to be a bad plug wire had burned in the boot and made that cylinder dead and I had a flashing light continuous .

Your problem is intermittent and will make it harder to find . Could be plug wire or a coil , or even a injector . You may have to get someone with a tech2 and plug up and go for a ride to see what is going on since it is only happening when you are driving . This could tell you what cylinder is .

If you are still running original wires its time for new ones anyway . I would start there .
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Old 09-16-2017, 10:57 AM   #5
Bladeboy1998
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Re: flashing check engine light

Could also be the crank position sensor, mine would blink at highway speeds, replaced it with a factory one, no problem since then
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Old 09-21-2017, 07:57 PM   #6
edhtrd71
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Re: flashing check engine light

A blinking check engine light does mean a misfire is happening. It blinks to worn you that it is enough of a misfire to damage the catalyst. I have never seen a truck blink the check engine light and not set a misfire code. A simple tune up with plugs and wires pretty much always fixes that problem on these truck. When you say all those items were checked already what do you mean by checked? How were they checked? I have seen plenty of knock sensors fail but they don't cause isolated misfires. You might want to try a different technician to take your truck to .
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