2012 Misfire P301, P302, P304
Results 1 to 6 of 6

This is a discussion on 2012 Misfire P301, P302, P304 within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Have had my 2012 to the dealer on two occasions for random misfires. First visit for P301, P302, P304, CELs. ...

  1. #1
    Registered User ea126405's Avatar
    Join Date
    Nov 2011
    Location
    Corn Country
    Posts
    221
    I Support ClubWRX

    2012 Misfire P301, P302, P304

    Have had my 2012 to the dealer on two occasions for random misfires. First visit for P301, P302, P304, CELs. Second visit P301, CEL. Car has 10K miles and is 100% stock.

    The car runs a bit rough at idle, on occasion. The codes were thrown just after starting car and driving (not fully warmed up).

    The first visit to the dealer resulted in a new ECU flash, which was designed to fix "random misfires" according to the service writer. BTW, the new flash has a MUCH smoother power curve with the car under boost, no more hitch at 3.6-3.7 RPMs, I'm thankful for that at least!

    Looks like the new flash is not the fix for the random misfire issue. At this point, the car is not misbehaving and the analysis shows normal (some roughness, yet no misfires). They have a call into Subaru and I will pick up the car today. Basically, they just reset the CEL.

    I don't want to play this "let's see if it gets worse" game (actually words from service writer).

    What do you think?
    '12 WRX Limited, 5-door -- Black

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    and the Funky Bunch Calvinball's Avatar
    Join Date
    Jan 2012
    Location
    Philly Area
    Posts
    5,971
    Can you clarify something? Have you had any more codes since the flash?
    - Will
    First Mods: What to do and what not to do
    Current Car: 2014 Golf TDI
    Previous Cars:2012 WRB WRX Hatch, 2004 RSX-S, 1998 Grand Prix GTP
    "Isn't it amazing how smart you feel when you just aren't being stupid?"

  4. #3
    Registered User ea126405's Avatar
    Join Date
    Nov 2011
    Location
    Corn Country
    Posts
    221
    I Support ClubWRX
    Yes, the second visit to the dealer was post-flash (P301).

    I picked up the car yesterday and this morning it threw another code right after I started it and began backing out of the driveway. I'll pull the codes when I get a chance and head back to the dealer.

    The flash provides me with a much better power curve, but apparently hasn't stopped the misfire(s).
    '12 WRX Limited, 5-door -- Black

  5. #4
    Registered User ea126405's Avatar
    Join Date
    Nov 2011
    Location
    Corn Country
    Posts
    221
    I Support ClubWRX
    I'll have mine back to dealer on Monday and I am hopeful that the 3rd time will be the charm. I swung by a few days ago and they were nice enough to pull codes, on the fly (no appt.). The light was actually off by then but the codes were stored. This time the dreaded P0451 showed up along with misfire 0301.

    Anyway, I got a call from the service advisor. Their master tech has been in touch with Subaru. The problem could be related to a harness issue, which he'll be looking at on Monday. Got my fingers crossed....
    '12 WRX Limited, 5-door -- Black

  6. #5
    Registered User ea126405's Avatar
    Join Date
    Nov 2011
    Location
    Corn Country
    Posts
    221
    I Support ClubWRX
    It has been about 2 weeks since I picked up my 2012 from the dealer. They are pretty certain the problem has been found and fixed. I spoke to the master mechanic who worked on it. He gave me a bit of detail regarding the fix and I'm happy to share it. The car is running fine, with no rough idle. We'll see how things go the next several days.

    He removed and replaced a butt connector, which is part of the engine wiring harness. The connector joins a Black/Yellow wire to 4 wires. The four wires are responsible for 8 separate functions. One of these functions has to do with the Manifold Pressure Sensor, which is where my problem manifests itself. At any rate, the repair entailed removing the butt connector, cleaning the wires, and replacing the butt connector. In order to get to the connector, he had to remove the butyl wrap and then re-wrap the harness when the fix was complete.

    My fingers are crossed that the problem is behind me for good. It is important to note that Subaru tech support is aware of this issue and potential fix. If you're back and forth to the dealer with this type of issue, be sure they get the Subaru support team involved.
    '12 WRX Limited, 5-door -- Black

  7. #6
    Registered User ea126405's Avatar
    Join Date
    Nov 2011
    Location
    Corn Country
    Posts
    221
    I Support ClubWRX
    Several thousand miles, no further misfires or evap codes.

    Case Closed!
    '12 WRX Limited, 5-door -- Black

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •