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Old 02-03-2005, 12:47 PM
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Cylinder Misfire

I hope you guys can help, this is for a 2000 Pontiac Grand AM.

I went to Autozone to get the codes read,

P0204
The PCM has determined that a malfunction exists in the electrical circuit for cylinder #4 fuel injector

P0304
The PCM has determined that a misfire has occured in cylinder #4

I have new plugs and wires from like 5~6 months ago. Could it be the coil pack? This is a semi-random problem, reoccuring every 2~3 months for a couple days at a time. I'm sure it'll run fine for another 3 months before it does it again. It seems to happen more often when it's damp or raining outside.

Quote:
DTC P0204 Injector 4 Control Circuit
Refer to Engine Controls Schematic Power, Ground, and Fuel Injectors .

Circuit Description
The PCM controls the fuel injector control circuit using a Multi Function Driver (MFD). The MFD has the ability to detect an electrical malfunction. If an electrical malfunction is detected, the MFD signals the PCM to set this DTC.

What that basically means is that there's a problem with injector #4s control components. If there isn't a short to ground, or a short to battery positive in the wiring harness, then you'll need to replace your PCM and have it reprogrammed.
This was my response on a grand am forum, you think you could help elaborate?

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Old 02-03-2005, 12:51 PM
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Make sure the injector plug is tight. Check t omake sure the pins aren't bent while youat it. Then lube with dialectric grease and see what happens. Otherwise Could be a bad injector or coil packs.
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Old 02-03-2005, 01:19 PM
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misfire

if you are getting P0204 then its just what it says. you have a bad circuit. which means you could have a short in the wiring, or a bad injector or a bad connection. check all the wires leading to the #4 injector. and if the injector isnt firing like its supposed to P0304 will show up because #4 will be misfiring because of no fuel so it trips that code. they are both linked. so check the wires and connection and if they look fine then its the injector. like the DTC says. thats what they're there for. good luck!
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Old 02-03-2005, 03:00 PM
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i replaced the #4 injector several months ago thinking that was the problem, so i don't think that's it. i'll get some of that dialectric grease to see if that helps. i've also got a spare coil pack i may stick in for good measure.
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Old 02-03-2005, 03:10 PM
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Just because you replaced the injector doesn't mean the wiring is good. Check the wiring to it as well.
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Old 02-03-2005, 03:11 PM
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wiring

pull the coil pack off and take it to your local outo parts store. they can check it there. usually for no price. they do around here anyways. and if thats good, check the plug wire... make sure theres a good connection and it wouldnt be a bad thing to put some of that dielectric grease on the plug and the terminal on the coil pack. and if all that checks out then i'd start looking for a short in the wiring harness for the injector and check the connection to the injector and do like johnsongrass says and put the grease on the connection to the injector. and after that im stumped. unless you got a faulty injector which can happen but is unlikely... unless you bought ACCEL injectors which are junk. but anyways check that stuff and let me know if ya find anything.
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Old 02-03-2005, 03:14 PM
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look down into the plug....

see its not dirty or has a broken or bent pin...pull on the wires to see if one is loose...could be a bad plug if you already changed the injector the only thing left is the plug or the coil...did you change out the coil to eliminate that?


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Old 02-03-2005, 03:20 PM
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Matts99Sierra hit one spot, if you have Accell products especially their plug wires they are junk also they do not last very long and give the problem when damp as described.
What do the plugs look like now?
Look at the wires at night and watch the spark jump all over the place.
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Old 02-03-2005, 04:08 PM
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rule out the coil pack by switching the wire with the other wire on that pack. Meaning each pack fires 2 cylinders, It is not uncommon to see a weak side of the coil pack. If it does move to the other cylinder it most likely is the coil packor the plug wire, if it does not move then it is in the wiring for the pulse of the injector.
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Old 02-03-2005, 09:47 PM
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There's a condition called "fretting" with the injector connections. It's corrosion that takes place between the connector terminals and the injector terminals. Usually if you disconnect the connector and reconnect it, the problem goes away for a while, then comes back weeks later. The easy fix is to coat the terminals with dielectric grease and reinstall. This also works on coil terminals ( secondary side) and module connectors.
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