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Flashing Cel Light?

crate

By crate
in Ask A GM Technician

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crate Enthusiast

crate

Posted
Posted

Had a code thats comes and goes at times, which is P0430 Catalyst System Efficiency Below Threshold (Bank 2), i'm pretty sure my pass cat is going or is gone,

but going to work today my cel started flashing, so decided to head back home, put the scanner on it and had 2 codes one was the p0430...and the new code was p0306 misfire cyl 6. only flashes when i drive, if at idle stopped i doesn't flash only driving..

 

could this code be from the cat problem? or something else to look at check?

 

Truck runs great, idles great no signs of anything except the loss of some power which i expect is from the 430 code....

 

truck is a 99 nbs 4.8 with 182k

bobcat5544 Enthusiast

bobcat5544

Posted
Posted

When the light flashes it means you have raw fuel being dumped into the exhaust system. With code p0306 you are misfiring on # 6 cylinder. So you have either a bad spark plug, spark plug wire, bad ignition coil, or wiring problem to the ignition coil.

 

At this time don't worry about code P0430 unless it comes back on after you fix the 1st problem.

crate Enthusiast

crate

Posted
  • Author
Posted

i've had the P0430 code for about 2 yrs off and on, would come, go away come back. the last few weeks it comes back pretty quick and finally found it was for the cat, plus the power on truck has started to get bad lately, the pass cat rattles like a sob if you hit ti with hand, and after trucks been setting a few days.

 

Sparkplugs where changed last years, wires where about 2 yrs ago or so

bobcat5544 Enthusiast

bobcat5544

Posted
Posted

If your cat rattles inside you need to replace it. It is probably broken down cloging your exhuast system. Which in turn can cause CEL light to flash since it can't get rid of the unburnt gas. The PCM could be blaming #6 cylinder for this problem when there is no problem there or with the clog you have now burnt the exhaust valves on #6 cylinder.

crate Enthusiast

crate

Posted
  • Author
Posted

sorry about that, wasn't paying attention this am when i post them, though i was somewhere else..

 

Anyways, after i erased the codes, i just went out now 1:30pm started truck no codes...drove into town 6 miles one way, no lights again..truck ran fine....got home, still no codes...put on scanner to check if pending codes and nothing..

 

I have noticed that only time it acts weired is early in the morning after i has set....well i just got new cats online...should be here by this weekend..

 

i did find on another board where if the cats are messed up/clodded, it can give you the misfire codes....once i get the new ones on and drive it see if it comes back,

 

did take #6 sparkplug out, and it looked perfectly fine..

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