Need help with PO 300 code
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3rd Gear
Joined: Apr 2008
Posts: 3
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Need help with PO 300 code
Hello, I am new to this forum and have a '99 C-5. I was hoping that some of you would be able to offer up some insights or suggestions concerning a problem I'm having.
The problem started this way: I was driving the car, a 99 C-5 for about 7 miles when the engine started missing. Turned around and limped home and parked it. Next day it ran ok for about 3 or 4 miles and then the same problem reoccured. Back to the barn and let it sit. I went through this routine several times with the distance that it ran getting progressively less each time. I pulled up a PO303 code-cyl 3 misfire detected. Right now if I start it it will run on 4 cylinders, The four on the passengers side all fire and the four on the drivers side are all dead. Checked the ignition fuses and both are good. In fact checked every fuse in there and they are all good. I can hear the injectors working, don't think it is a fuel problem, I know the fuel pump is working. Put in new plugs when the problem occured, car has about 21,000 on it. I figure that someone else has been down this road before and might be able to shed some light on the problem. Thanks for the imput. Don
The problem started this way: I was driving the car, a 99 C-5 for about 7 miles when the engine started missing. Turned around and limped home and parked it. Next day it ran ok for about 3 or 4 miles and then the same problem reoccured. Back to the barn and let it sit. I went through this routine several times with the distance that it ran getting progressively less each time. I pulled up a PO303 code-cyl 3 misfire detected. Right now if I start it it will run on 4 cylinders, The four on the passengers side all fire and the four on the drivers side are all dead. Checked the ignition fuses and both are good. In fact checked every fuse in there and they are all good. I can hear the injectors working, don't think it is a fuel problem, I know the fuel pump is working. Put in new plugs when the problem occured, car has about 21,000 on it. I figure that someone else has been down this road before and might be able to shed some light on the problem. Thanks for the imput. Don
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
The code is a P0300 ("P" followed by 4 numbers "0300") in case you are trying to SEARCH on the code .... all DTC are a letter (P=Powertrain, C=Chassis, B=Body, U=Communications) followed by 4 numbers (1234 .... 1001 ..... 0300 .... whatever).
Double check Fuse 22 (15 Amp) in the Underhood Fuse Block as it supplies power to the driver's side coils.
Check G107 ... it is located on the driver's side of the engine block .... toward the rear and high on the block.
If one side of the engine has all the plugs firing, and the other side is not firing, either you are not providing power to that side ... or that side has lost its ground.
Sounds like a broken or disconnected wire to me....
Good luck,
Double check Fuse 22 (15 Amp) in the Underhood Fuse Block as it supplies power to the driver's side coils.
Check G107 ... it is located on the driver's side of the engine block .... toward the rear and high on the block.
If one side of the engine has all the plugs firing, and the other side is not firing, either you are not providing power to that side ... or that side has lost its ground.
Sounds like a broken or disconnected wire to me....
Good luck,
