Author Topic: Codes p0300 and p0621 help ???  (Read 656 times)

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Offline Monster762

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Codes p0300 and p0621 help ???
« on: Aug 15, 2015, 04:44 PM »
Ok I have an 06 impala ss with about 130000 miles today I had a lot of groceries in car and getting onto the highway I had to accelerate a little fast. At about 65-70 mph my check engine light started blinking. No noticeable  difference  in performance though. I checked for codes and p0300 and p0621 came up stating multiple misfires. The engine light went off a minute or so after it started  blinking. Looking up online it says could be ignition control module or 02 sensors or any number of things. I have new plugs and wires about a month old now. Anyone had this problem that can give me any info to help start me in the right direction. And if I just replace icm will I have to do anything  other than just change the part? They aren't expensive on rockauto I just want to be sure there isn't any need for a chevy dealer. Is it a do it you self. Thanks in advance for any help
06 impala ss  factory bose rear deck jbl doors with sundown audio sub,3cubic ft band pass alpine amp, 20% tint , a lot of suspension redone with Moog,kyb struts ,drilled slotted rotors,carbon pads,black headlights,rebuilt trans, backyard intake w/K&N filter,3 in exhaust all the way back. Dod delete(software not hardware). P zero tires factory rims

Offline JaySS

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Re: Codes p0300 and p0621 help ???
« Reply #1 on: Aug 17, 2015, 06:46 AM »
I would double check you wires, that they connected to the coils and plugs. Some of them can be a pain pushing down on, to get connected. I always use some ele. grease to make sure no moisture gets in. Then clear the codes and test drive to see if the code come back.
2006 SS Impala "The Bitterness of Poor Quality Remains Long After the Sweetness of Low Price is Forgotten"

Offline Monster762

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Re: Codes p0300 and p0621 help ???
« Reply #2 on: Aug 17, 2015, 12:10 PM »
Ok I will double check them and clear code . It's been a few days and the check engine never came on again. It was just blinking that one time.   thanks
06 impala ss  factory bose rear deck jbl doors with sundown audio sub,3cubic ft band pass alpine amp, 20% tint , a lot of suspension redone with Moog,kyb struts ,drilled slotted rotors,carbon pads,black headlights,rebuilt trans, backyard intake w/K&N filter,3 in exhaust all the way back. Dod delete(software not hardware). P zero tires factory rims

Offline 2007SSImpala

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Re: Codes p0300 and p0621 help ???
« Reply #3 on: Oct 12, 2015, 06:48 PM »
I'd be a little worried about that P0621. If your voltage to all your electrical components is fluctuating below 12 volts for a certain period of time, these modules in the car don't know how to act. You could see engine misfires due to lack of voltage. That DTC is a Gen L Terminal circuit. Id pull that connector off of the generator and check the pins inside of it for spreading or terminal fretting. Apply some dielectric grease to it ad re evaluate. A circuit issue will come and go. The car may seem ok for now.

Offline Monster762

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Re: Codes p0300 and p0621 help ???
« Reply #4 on: Oct 27, 2015, 03:18 PM »
OK the alternator clip with wires doesn't clip anymore for some reason could that be it. Please explain a little better cause I do experience what I think is voltage drop but can't figure where to start. Alt and battery are new and test good but the clip of wires to alt doesnt snap on tight. I get serious headlight dimming with stereo and only run around 600 rms. It feels like it drives different like not as responsive sometimes too. Also headlights dim if I press window buttons. With stereo off. I also get serious surges to my sub when I have car off radio off and open trunk sometimes. I have checked all grounds to stereo. All solid. I added 0 gauge ground from block to chassis and battery neg to chassis too. Any help appreciated. Thanks.
06 impala ss  factory bose rear deck jbl doors with sundown audio sub,3cubic ft band pass alpine amp, 20% tint , a lot of suspension redone with Moog,kyb struts ,drilled slotted rotors,carbon pads,black headlights,rebuilt trans, backyard intake w/K&N filter,3 in exhaust all the way back. Dod delete(software not hardware). P zero tires factory rims