Codes PO300, PO301, PO303, PO304

Hi,

I look through the pics you attached. I noted that the short-term fuel trims are both at 0. In a perfect world, that is great, but I've never seen both at 0 for any period of time.

When you checked this, was the engine at operating temperature? Also, by chance do you have the coolant temperature sensor reading when the engine is cold?

The idea that the same codes come back could mean several different things. If you haven't already, clear the codes and see if they all come back. Also, are you able to scan the entire can-bus? CAN stands for controller area network. All the modules are tied together via a few wires. If there is something stored in a different module, it should identify it.

Here is a video showing it being done:

https://youtu.be/InIlnsjOVFA

Let me know about the trims you posted and the ECT signal.

Thanks,

Joe

Hi,

It looks like the engine is running rich (too much fuel). I noticed the fuel trims are not at 0. They indicate -7 which means the computer is trying to lessen the amount of fuel being put into the engine based on the oxygen sensors readings.

Have you checked the fuel pressure and fuel pressure drop-off? We may have an issue with high fuel pressure, an injector leaking, a faulty module, or a regulator issue. In my mind, I would suspect a leaking injector in the affected cylinders, but you need to check first.

If you haven't already, take a look through this link. It explains how to test fuel pressure and the regulator.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Next, if you look at pic 1 below, it shows the manufacturer's fuel pressure specifications. The additional pics are the leak-down test specific to this vehicle.

Try this and let me know what you find.

Joe

See pics below:

Note: You will need a fuel pressure gauge to perform this, and I know most people don't own one. If that is the case, a lot of parts stores will lend one to you.