Error Codes P0300 and P0301
Thread Starter
Super Member
Joined: Aug 2003
Posts: 626
Likes: 3
From: Los Angeles, CA
'03 E55 (My Daily), '01 ML 320 (Wifey), Twin Turbo '69 Camaro (In Progess)
Error Codes P0300 and P0301
My wife's car through a CEL yesterday and began running rough as though it was missing on a cylinder. Strange thing I also noticed was that the BAS/ESP light also came on. I read through the forums and learned that these are pretty generic fault codes, though the P0301 indicates a misfire in cylinder one. I checked the fire with an extra spark plug in the first cylinder (which I assume is the first cylinder on the driver's side bank) and had plenty of spark so I ruled out the ignition coil. Next thought was that the MAF was bad, so I replaced it and the engine is still running rough. The fuel filter has never been changed so I am about to tackle that, but I want to avoid throwing parts at the car to get it fixed. Any insight from others who have had this issue is greatly appreciated!
Thread Starter
Super Member
Joined: Aug 2003
Posts: 626
Likes: 3
From: Los Angeles, CA
'03 E55 (My Daily), '01 ML 320 (Wifey), Twin Turbo '69 Camaro (In Progess)
Found out that cylinder 1 was on the right bank and didn't feel like spending all day replacing the fuel filter, though it needs to be replaced. Needless to say, I considered the possibility that my catalytic converter may be clogged. I pulled the first 02 sensor (pre-cat) and started up the car. It immediately ran smoother and the CEL turned off. While this method doesn't allow you to determine whether or not the primary or secondary cat is bad, it has at least allowed me to troubleshoot that the cat is the culprit.
Anyone know of a good source for cats? I want to avoid the dealer (and their markup) if at all possible.
Thanks in advance for the assistance!
Anyone know of a good source for cats? I want to avoid the dealer (and their markup) if at all possible.
Thanks in advance for the assistance!
