P0304 Lexus - 2005 es330

Question

Is there a way I can clear the codes on my 2005 lexus es330? I had the codes pulled with an OBDII reader and it indicated that I had a faulty fuel cap. I didn't immediately replace it that day however the second day I had a strong rough Idle and loss of some power... I had new codes pulled and this time it indicated PO174 small leak detected possible loose or faulty fuel cap, PO456 small leak detected with the same possiblity of a missing or loose fuel cap. PO442 small leak detected with the same possiblity of a missing or loose fuel cap,PO304 cylinder 4 misfired, PO354 Ignition coil 4 primary/secondary circuit...

Could it just simply a fuel cap problem? If so, could clearing the codes (now I have the new cap installed) resolve the missing/rough idle?

Answer 1

P0354 is most likely for a bad coil which has nothing to do with the codes P0442 and P0456 

For P0442 and P0456 I would say start by replacing the gas cap with a Factory gas cap.

For P0174 I would try to clean the mass air flow sensor for.

Possible causes

- Intake air leaks

- Faulty front heated oxygen sensor

- Ignition misfiring 

- Faulty fuel injectors 

- Exhaust gas leaks

- Incorrect fuel pressure

- Lack of fuel

- Faulty Mass Air Flow (MAF) sensor

- Incorrect Positive Crankcase Ventilation (PCV) hose connection