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Mike O.
Mike O., Master Technician
Category: Nissan
Satisfied Customers: 427
Experience:  18 years with Nissan/Infiniti dealerships
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Nissan/Datsun Altima SE How do I get rid of a P0300 multiple

Customer Question

How do I get rid of a P0300 multiple misfire code?
Submitted: 6 years ago.
Category: Nissan
Expert:  Mike O. replied 6 years ago.

Mike O. :

Hi my name's XXXXX XXXXX for the question!

Mike O. :

Well it's highly unlikely that the cats are causing a misfire code, however a misfiring engine can cause damage to the cats so maybe that's where those shops are mistaken. There are a few common things on altimas that will cause that code. First, check the ground cable from the battery to the transmission. If it's frayed or broken, it will need to be replaced. The ignition coils will definitely cause a misfire especially if you see that the tops of the coils are blistered or melted. Also the injectors tend to go bad on altimas. You'll need a ohmeter to check the resistance across the injectors to see if they're ok or not.

Mike O. :

It is possible that all the injectors are bad or just one is bad and is affecting the bank of incident cylinders causing the multi-cylinder misfire so you'll need to check them all to be sure. If you have an ohmeter let me know and i'll tell you an easy way to check them. I would rule out the catalytic converters for now if I were you.


I don't think everything got sent last night.

I have a 2005 Nissan Altima SE3.5. It is a rebuilt salvage that was hit on the right front. Airbags/front seatbelts dont work. I bought the car from a thrid party after it was wrecked and "fixed". When I bought the car in march it had been sitting for 3 years and had 31000 miles, now it has 41000. Since I have bought the car I've been trying to get rid of a multiple misfire that seems impossible as its been taken to 8 different shops. They all concluded it was the catalytic converters. The 2 in front were for some reason hollowed out. I replaced all 3. No change. I replaced all spark plugs, O2 sensors, air/fuel ratio sensor, plentum gasket, fuel system tune up, bought a new ecm, the dealer tried to install but car wouldnt start so switch back to the one that was in it. I finally had it towed to 80 miles to a guy that started at the variable induction control silenoid. He put a GM part on there just to see if it'd make a differnce before spending the money. He also unplugged an O2 sensor then drove it for about 15 minutes. Not sure how but the misfire was gone. A month and a half later my codes were pulled and cleared and the misfire came back immediatly . Ive tried to get rid of it and have spent too much money. Why did clearing the codes cause the code to come back? and how do I get rid of it for good? Please help. Ive tried to educate myself on this issue but it doesn't seem to be able to be pinpointed. Thank You in advance