P0300 and P0174

JustLostOne

JustLostOne

New Member
Joined
May 17, 2020
Messages
13
Location
Anne Arundel County, Maryland
So I've got 2 codes coming up, p0300 and p0174. I've checked plugs and changed wires cause 2 of them broke while getting them off. What else could be the problem? It was fine there day before and went out to go to work and it was running rough and then the codes came up.
 
What Causes a P0300 Code?
  • Low Fuel Pressure
  • Vacuum Leak
  • EGR system malfunction
  • Internal Engine Problems (such as low compression)
What causes the P0174 code?
  • An air leak after the mass air flow (MAF) sensor, such as a torn intake boot, or bad intake manifold gaskets
  • A dirty or faulty mass air flow sensor
  • Faulty oxygen sensor
  • Incorrect fuel pressure
  • Leaking positive crankcase ventilation (PCV) valve
  • Clogged exhaust gas recirculation (EGR) Port
  • Leaking brake booster
If it were me I would start by checking the fuel pressure and making sure it's where it needs to be.

I would then run a smoke test on the vacuum system and the EGR system to rule those out, as vacuum and EGR leaks can be very hard to find without a smoke test.

I'd also inspect the crankcase vent hoses and if it comes down to it, test the O2 sensors to make sure they are good. There is a procedure in the FSM to test them.

In addition, O2 sensors are general wear-and-tear maintenance items. They should be replaced every 80k miles or so, regardless of whether they are throwing codes or not.
 
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