Hello folks,
I've got a 2009 Fit with a manual transmission.
This thing has new EGR and coils and plugs.
I get a misfire on cylinder 4 (code P0304) after 10-15 seconds of idling after startup, and the Check Engine Light starts blinking
The O2 Sensor on the scanner live data starts at 1.25v at the time the car starts up. Then, it drops to 0.00v at the time the light starts blinking.
There is another O2 sensor entry in the live data that says O2s11 which I looked up and it means "O2 sensor current (wide range)." The value for that is -0.273 mA
The Fuel System on the scanner says "OL_Fault" for I guess Open Loop Fault
The Short term and Long term Fuel trim are both 0
The MAF (Mass Airflow Sensor) reads 2.69
The ECT reads 67 degrees celcius
The EGR Error is 99.2 %
The EGR Command value is 0
When I have driven the car in this state there is very poor power, it idles but won't really go nowhere

What's up with that? Would you replace the upstream O2 sensor?

Thanks for whatever you got.

 

Update

I replaced the Upstream O2 Sensor, and I still get the same behaviour.

Can anyone help me understand why the volts on the 02 sensor goes to zero and the fuel system goes into Open Loop Fault?

I would be quite appreciative of any tips.

 

Hello all-

Still misfire on cylinder 4 P0304 with check engine light blinking. New coils, new plugs, new O2 sensor.

Mechanic checked it out with these results:
- compression OK on cylinder 4
- spark OK on cylinder 4
- fuel injector OK on cylinder 4
- ** NO ground on fuel injector. *** So, the ECU isn't providing the ground to fire the injector.

Mechanic recommends new ECU and programming from the dealership.

I'm looking at the Crankshaft Position Sensor and the Camshaft position sensor. Does one of these send information to the ECU for timing the firing of the fuel injector? I think that I read somewhere that one of these sensors could affect that.

Thanks for any help!

 

I would like to believe that both the Crank position sensor AND the Cam position sensor play a role in determining where the engine is during the cycles. I think without those the engine would not run properly.. Now that being said.. if 1 2 and 3 cylinders are working and firing.. and Cylinder 4 is not.. I would think the ECU is not sending the signal for it to fire or send fuel. or Both. Or connection somewhere is faulty. If mechanic said it is not sending a ground.. that might be the answer.

 

Good thoughts thanks Mykizism.
Replacing the ECU isn't an option for me at least not by a dealership because it's gonna be too costly. I noticed that there's some precedence for replacing the ECU on the cheap, by swapping out components from the old one: https://honda-tech.com/forums/engine...uired-3295937/

I think i'll try and find the CKP and CMP and see if they look ok. It seems that replacing them both wouldn't be too costly.

I'm wondering if there could be a possibility that there's a problem on all cylinders, with only the 4th being reported. Or if there was a misfire on all, would there be 4 misfire codes?

 

You have the option of finding a used ECU from a yard and having it reprogrammed to the car at the dealer.

 

The car is working!

This discussion from cutsheal5 is what solved this for me: https://www.fitfreak.net/forums/2nd-...inder-4-a.html

I replaced the mosfets in the ECU after purchasing a spare ECU to harvest some working chips, and using a "rework station" on which there are many youtube tutorials.

For anyone in this position in the future searching this forum for "mosfet" or "ssd103" may be productive. Thanks cutsheal5 for the specs on the injectors and clips etc.