So I was driving into work this morning. I was passing some cars, not terribly fast, but fast enough, 85-90.

I noticed my CEL started flashing. It flashed for about 10sec then went out.

This is a 2006 Sierra, 5.3L Flex engine.

Mods:

AirRaid MIT
Nelson 93 tune
4.11 gears

I last changed the plugs/wires about 4-5k miles ago. I used AC/Delco Iridium tipped plugs (I doubled checked the gap) and Taylor 10mm wires. This engine has coil packs as well.

Thoughts? I know I need to get it scanned but any assumptions? Coil pack(s)? Cats?

Thanks in advance

 

better find out the code,
when the light flashes it means Catalytic failure imminent
so i'd avoid driving it around and potentially being up for an engine, get the code and then we'll figure it out!

 

most guys get this when running very rich or with big cams on decel.. it basicly happens when your o2's see to much fuel in the exhaust

 

Please correct me on this but I thought I read somewhere in the owners manual that when that light flashes - severe engine damage may have occurred due to knock-

My 02 does this when towing a heavy trailer in 3rd doing 65 mph going up hill. I changed my plugs and haven't seen it sense

I'm now wondering what really was going on with it

 

no its when there is a "miss fire" or so the computer thinks there is.. i get it going down hill about 2300-2500 rpms.. running rich

 

Okay thanks for clearing that up

 

Flashing CEL is generally not a warning of severe engine damage, it usually indicates an immediate condition such as a misfire that is posing a significant threat to the life of the catalytic converters. "Knock" is a form of a misfire, but usually the truck is able to adjust the timing to a point where it will not damage the engine.