Randomly Occurring Flashing Check Engine Light

Anastasios Tziolis · March 27, 2021

I have a 2016 Chevy Tahoe 105,000 miles. Twice last week a few days apart my check engine light began flashing about 15-20 minutes into my commute and turned off within about 1-2 minutes both times. My spark plugs were replaced at 97,576 miles last October at the dealership and the coils, boots, etc, were inspected . I’ve been told that putting a tank of high quality supreme grade gas could help the problem. Has anyone else had this issue?

Edited March 27, 2021 by Anastasios Tziolis

cs15dah · March 27, 2021

Flashing may mean there’s a misfire going on. Check for pending DTCs. Does the flashing maintenance indicator light happen when you’re accelerating or cruising?

Quality fuel is always good and always should be used. But 87 octane is all you need. “Supreme” does nothing for you. That word is simply a marketing scheme. These trucks do not require high octane. Folks have mixed outcomes with using a fuel injection/system cleaner. The likely hood that this’ll help your problem is awfully low, but may be worth a shot. You can buy fuel injector/system cleaner locally, or just use high quality detergent fuels.

reardiff · March 30, 2021

On 3/27/2021 at 3:45 AM, cs15dah said:

Flashing may mean there’s a misfire going on. Check for pending DTCs. Does the flashing maintenance indicator light happen when you’re accelerating or cruising?

Quality fuel is always good and always should be used. But 87 octane is all you need. “Supreme” does nothing for you. That word is simply a marketing scheme. These trucks do not require high octane. Folks have mixed outcomes with using a fuel injection/system cleaner. The likely hood that this’ll help your problem is awfully low, but may be worth a shot. You can buy fuel injector/system cleaner locally, or just use high quality detergent fuels.

Unless you have the 6.2 which does recommend premium fuel.

nfisherman · March 30, 2021

It's hard to say what's wrong without knowing which code was generated. I had a similar problem with my 2015 Sierra. I don't recall the specific code, but it was related to a faulty catalytic converter. I had been using 87 octane gas from a cheap gas station near my office almost exclusively. I went to a station that advertised top tier gas. I filled up with a tank of 93 octane. It worked for me. The light went off after about 200 miles. You might want to give that a try. It won't hurt anything.

MDP1 · June 12

My 2015 yukon xl denali with 195k miles, has had a check engine light on for 6 months. Periodically, it begins flashing, begins to run really rough. Then, it stops and runs smoothly. I have taken it to multiple places, including the dealer without someone finding the problem. I have replaced many things...,full tune up, CAT, O2 senors, MAF, high pressure pump, transmission coolant lines, air ride compressor, new struts, front shocks and coil springs, etc. I suggested replacing the ECM....they all think I'm crazy when I suggest this could be the problem. Am I wrong/crazy or have I drove the last miles on this vehicle?

asilverblazer · June 12

18 hours ago, MDP1 said:

My 2015 yukon xl denali with 195k miles, has had a check engine light on for 6 months. Periodically, it begins flashing, begins to run really rough. Then, it stops and runs smoothly. I have taken it to multiple places, including the dealer without someone finding the problem. I have replaced many things...,full tune up, CAT, O2 senors, MAF, high pressure pump, transmission coolant lines, air ride compressor, new struts, front shocks and coil springs, etc. I suggested replacing the ECM....they all think I'm crazy when I suggest this could be the problem. Am I wrong/crazy or have I drove the last miles on this vehicle?

ECM's rarely fail and they even more rarely fail intermittently. Many parts you replaced are unrelated to a check engine light.

Full tune up, what did this include?

CAT, the engine has been running poorly enough for an extended period of time to kill the catalytic converter?

O2 sensors, why?

MAF, why?

High pressure pump, why?

What are the current trouble codes?

Transmission coolant lines, air ride compressor, new struts, front shocks and coil springs are not related to the engine running poorly.

newdude · June 12

18 hours ago, MDP1 said:

My 2015 yukon xl denali with 195k miles, has had a check engine light on for 6 months. Periodically, it begins flashing, begins to run really rough. Then, it stops and runs smoothly. I have taken it to multiple places, including the dealer without someone finding the problem. I have replaced many things...,full tune up, CAT, O2 senors, MAF, high pressure pump, transmission coolant lines, air ride compressor, new struts, front shocks and coil springs, etc. I suggested replacing the ECM....they all think I'm crazy when I suggest this could be the problem. Am I wrong/crazy or have I drove the last miles on this vehicle?

Flashing = misfire or detonation that can lead to engine damage.

Shotgunned a lot of parts for what likely sounds like a mechanical engine issue, especially being a 6.2. Assuming plugs and wires are all tight, bad AFM lifter, bad camshaft from a spun lifter, things like that are what you might have going on.