Multiple Misfire cylinders - Code P0300

[rapaulino29]

Hello Forum Members,

I am a new member and I need help with my wife RX-300 2002.  The car has 251K miles and It is starting to fail on her.  The engine light came on and the scanner read the following codes:

P0300 - Multiple Cylinders Misfired

Bank 1, Bank 3, Bank 5, and Bank 6

 

How serious is this?  I understand that working on bank 1, 3, and 5 is very difficult.  Help!

 

Thanks in advance,

 

Raphael

[Filehorse]

If all these codes appeared at the same time it would seem they have a common cause such as a bad connection in the coil harness or the fuel injection harness. Ignition coils are a common problem with this generation RX but they would fail individually. Fuel pressure is another common source that would cause multiple misfires simultaneously. Here is a link which discusses the P0300 code for your Lexus and that might help. https://www.autocodes.com/p0300_lexus.html#disq  I also would not discount the camshaft position sensors or the crankshaft position sensors as they can also create havoc with the engine control system.

Given the age of the vehicle and the mileage you should think carefully before throwing a lot of money at the vehicle in search of the cause and then the repair. Good luck.

 

[Lexus Owners Club]

On 3/28/2021 at 12:31 PM, Filehorse said:

If all these codes appeared at the same time it would seem they have a common cause such as a bad connection in the coil harness or the fuel injection harness. Ignition coils are a common problem with this generation RX but they would fail individually.

 

I agree, more than likely some corrosion in the connections to cause all of the cylinders to go down at the same time