2003 Tahoe flashing check engine light

[Tonyrodz]

Probably his is non-Flex. FF trucks this year have a fuel filter.

@garren19714 are you sure it's a 4.6L?

Hard to believe that a flashing CEL would not have a current or history code.

Mine is also non FF.

 

[rockola1971]

@garren19714 Your Tahoe has a 4.6L Nortstar engine in it or did you mean a 4.8L? "I should also say it or firing on the passenger side of the motor but not the drivers side." Im assuming you are saying that the engine is not firing on drivers side of engine. What leads you to believe that? If that is true then the only things I can think of common to one whole side of the engine is the PCM, Ground for either ignition coils or fuel injectors and thats about it other than the exhaust. (one side of it).
A flashing CEL means you have active misfiring happening in the engine. Did you check for pending codes?

 

[MassHoe04]

Yeah... Flashing CEL has to have codes. We can speed up this process BIG TIME, if you can get the codes that were triggered. Even the cheapest basic scan tool will tell you what is there, which would be the best place to start.

I would not drive it to a shop or part store to get codes read. Flashing CEL indicates a serious condition and should not be running or driven anywhere. Probably not a good idea to even start it, if that can be avoided.

 

[RAMurphy]

OK, no codes that is a little unique but can happen I believe. What code reader are you using? Is t compatible with your vehicle? Is the software current? Have you tried a different reader? You could try to get a parts store to try and read the code. They do it for free. Essentially I agree with @Fless about no codes.

 

[Scottydoggs]

Yeah... Flashing CEL has to have codes. We can speed up this process BIG TIME, if you can get the codes that were triggered. Even the cheapest basic scan tool will tell you what is there, which would be the best place to start.

I would not drive it to a shop or part store to get codes read. Flashing CEL indicates a serious condition and should not be running or driven anywhere. Probably not a good idea to even start it, if that can be avoided.

not necessarily, if the cel lights not on yet, theres a pending code there. but it will clear when you turn the truck off. why i suggested making the light flash, then scan it running.

flashing cel generally means 1 of 2 items are bad. needs a tune up super bad, but i think he said he did plugs and wires. so that leaves the cats, could be clogged up. both cause a p0300 code, multiple misfires. so if you find the p0300 code. check cat temps before and after the cat, pre cat and cat will be super hot, after the cat much cooler due it being clogged up. temp lasers work great for this test. or drive it hard at night and get under the truck looking for the cats to be glowing red.

 

[Fless]

The OP may want to be sure all cylinders are firing before further diag.

 

[MassHoe04]

not necessarily, if the cel lights not on yet, theres a pending code there. but it will clear when you turn the truck off. why i suggested making the light flash, then scan it running.

flashing cel generally means 1 of 2 items are bad. needs a tune up super bad, but i think he said he did plugs and wires. so that leaves the cats, could be clogged up. both cause a p0300 code, multiple misfires. so if you find the p0300 code. check cat temps before and after the cat, pre cat and cat will be super hot, after the cat much cooler due it being clogged up. temp lasers work great for this test. or drive it hard at night and get under the truck looking for the cats to be glowing red.

OP's title for this thread included "CEL Flashing"...

GM Owner's manual mentions this on CEL:
"Light Flashing — A misfire condition has been
detected. A misfire increases vehicle emissions
and may damage the emission control system on
your vehicle. Diagnosis and service may be
required."

Anything rising to the level of making the CEL flash would have a code stored, even if it is only pending.

Before I got my Tech 2, I saw pending codes on my system with my Zurich scanner from Harbor Freight.
I didn't even have an active CEL on mine and was able to see a history of codes that were either old or still pending.
A lot were things like brake lamp and other issues that were repaired by the previous owner, but they didn't fully wipe the code history after the repairs were complete.
I found them under the GM OEM Enhanced sub-menu.

Anyway... I was just saying that there should be a history record of all stored and pending codes that the OP should be able to access to see what was going on.
I could be wrong, but I don't think pending codes just disappear when the engine is shut off. I am pretty sure the computer just sits on them until enough errors are collected to trip the CEL warning on the cluster.

 

[RAMurphy]

That is my understanding too. My scanners (both the direct plug in and my Bluetooth scanner) will display pending and short term history.

 

[MassHoe04]

If it were a serious misfire issue, as indicated by the flashing CEL, I probably would not want to be driving it to the parts store for a free code scan. There could be some potential for some damage somewhere. If OP doesn't already have a scan tool, He might want to get a ride down to Harbor Freight to pick something up, rather than wreck something if it can be avoided.

 

[RAMurphy]

Agree..