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2004 GTP Check Engine Light flashes

P

p coico

New member
When coming down a steep, long grade from about 4000 ft elevation ( Grapevine on I5, north of Los Angeles ) at highway speeds (65 to 70mph) my CEL will flash on and off several times, only staying on for about 5 to 10 seconds.
Otherwise, CEL is never on.
Engine seems to be running fine. No codes.
It's a stock GTP.
Anyone have this happen ?
What was the cause ?
Thanks...
 


Usually a flashing CEL is an active misfire that may damage the cat converter. Next time it does it scan the car w/o shutting it off and see if you can pull a code.
 
flashing cel means you need a tune up real bad, or the cats clogged up causing the misfires. next time it does it, scan for codes engine running, dont turn it off or the pending code will clear on you.
 
OK. I drove the car some more at highway speeds and did get two pending codes after the CEL flashed once or twice .....
P0137 [ O2 Sensor circuit low voltage B1S2 ]
and P0303 [ Cylinder 3 misfire ].
Then I shut the car off, let it cool down a bit, then drove it again at highway speeds and the CEL came on and stayed on. Pulled P0303 code at that point,
with none pending.
Engine appears to run fine. Plugs and wires were changed when I did the LIM and UIM gaskets back in March timeframe. Also put new o-rings on all
the fuel injectors then.
I did have a P0420 [ Cat Sys Eff below threshold - Bank 1 ] set the CEL several months ago. But I cleared it and it has not come back.
I have never seen P0137 or P0303 before this.
 
Yeah. My first guess was the coil. They are original and the car has about 133,000 miles on it and I believe the coils are original.
I see the AC Delco unit on RockAuto for about $40.
Is there any way to test them ?
 


swap that coil with one of the others, see if the misfire moves. (plug wires need to go where they started, so you only move the coil, not the wires off them) if it dont move swap the spark plug wire with the plug next to it, if it still dont move pull the spark plug check its not smashed, or has a crack in the porcelain.

if it still dont move after all that jazz the icm, or a injector could be the cause. injector swap with the one next to it would be the next free test. then you can get the icm tested at autozone part stores and others im sure.
 
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