P0300, P0303, AND P0303 codes on my VW CC with intermittent engine light blinking

volkswagen

#1

Hello,

My 2011 CC LUX 2.0T has been intermittently acting up all year, with Automatic (which I highly recommend) telling me there is something wrong. The codes are pretty wide-ranging in the diagnosis, and my mechanic has tried replacing the ignition coils with brand new OEM parts from Bosch. Yesterday, I had him replace an intake value sensor because it was leaking oil. I don’t think he has replaced the spark plugs, though, and this is one of the items listed in the codes that could be the culprit.

The car is actually worse today, and now my car has the three codes listed in the subject line. The engine light is blinking intermittently, which means I shouldn’t drive it. I promptly turned around when the light started flashing and parked the car in my garage.

Has anyone else seen this issue and do you have any recommendations?

Thank you!

Ryan


#2

You haven’t actually posted the issues so how can we respond? How about posting the actual codes you are getting? What is “Automatic”?? The transmission description or a diagnostic app?


#3

My apologies. My subject line lists the diagnostic codes. Specifically, the car kind of “sputters” or hesitates when I accelerate.



Automatic is an OBD II port tool that can read your engine’s diagnostic codes and let you know what, exactly, is wrong. However, these diagnostic codes list about ten different issues that could be the problem.


#4

Are you telling your mechanic what to do to fix the car rather than having them diagnose the problem and fix it? If you are doing that, Stop. You cannot determine everything from an OBD2 reader. You will throw a lot of parts at the problem - Bosch coils - and it won’t be fixed. And given the blinking light, it clearly isn’t fixed!

Pull all the spark plugs, do a compression test. If you find a bad cylinder, it is a mechanical problem, not an ignition problem. Compression good? Install new spark plugs (and wires if this is not a plug-on-coil). Start 'er up… blinking light? Check fuel pressure. Not in spec? Fuel pressure regulator or pump is bad. Noid lights will help determine if injector drivers are OK, Ohm out the injectors - are they all the same? No? Bad injector! One may be stuck open because crud is inside, bad injector!

This is the path your mechanic will likely follow if you let them do their job. If they aren’t capable, find a better one. Good Luck!


#5

I’m not telling them what to do, or how to do their job. I’m only using Automatic’s OBD II message relay as a point of reference. They said the coils were bad, which is odd because they replaced those 18 months ago. I replaced all four ignition coils again with OEM parts, and the issues not only persist, but they are worse.

Thank you for the advice. I should probably take the car to a VW dealer instead of a general mechanic. Even if VW charges more for the diagnostic, they’ll probably diagnose the problem correctly.


#6

The p030x codes are saying the computer is detecting misfires. That means it isn’t seeing the expected acceleration of the crankshaft rotation after the spark plug fires for that particular cylinder. It uses the crankshaft position sensor to determine that, so if that sensor wasn’t working this could result. Other causes are

  • a/f ratio problem (fuel pressure, etc)
  • compression problem
  • bad gasoline
  • spark problem (coil, spark plug, ignition module, battery/alternator)

You shop diagnoses these kinds of problems all the time most likely and should be able to get to the bottom of it eventually. They’ll use their diagnostic experience to determine what’s the most likely cause and will eliminate that first. But it may take several iterations. If I had that problem I’d do a visual spark test first, makin sure the spark quality at the spark plug is a strong healthy blue-white.


#7

Thanks, @George_San_Jose1! I have been reading up on these codes for much of the afternoon, and it certainly sounds like spark plugs. I don’t think the mechanic every replaced these. However, I will also ask my mechanics to look at the TSI PCV Valve, which is a common point of failure in VWs. https://www.youtube.com/watch?v=hQEciqR1ST8


#8

A faulty PCV system can cause an overly lean a/f mixture, and result in misfires. Definitely on the list of suspects. A fuel trim measurement – easy for a shop to do – might show an overly lean mixture, consistent w/a pcv system problem.