300M misfire code P0302 -> no coil codes, no injector codes?

Discussion in 'Chrysler 300' started by MoPar Man, Oct 31, 2007.

  1. MoPar Man

    MoPar Man Guest

    Just today my '00 300M started running rough. Most noticable at idle
    - like a cylinder not firing.

    Engine light came on.

    After parking it for a while, and starting it, it idles rough, but no
    engine light. Engine light only comes on if I drive it a little.

    Codes displayed on odometer are P1684 and P0302.

    The 1684 is a battery disconnect code (it has the original battery,
    which hasn't been disconnected for years - if ever, so perhaps this is
    an indication of a weak battery - although it turns the engine over
    just fine when cold). The 1684 code is said to not be responsible for
    the check-engine light.

    The P0302 code (if I'm right) indicates misfire in cylinder 2. This


    says that I should also expect to see either a coil code that
    corresponds to the same cylinder (P0351 to P0358) or a code that
    indicates an open or shorted injector in that cylinder (P0201 to
    P0208). I don't see any of those codes. Just 1684 and 0302.

    Might this set of conditions represent just a bad plug then? (orginal

    Car is exactly 8 years old tommorrow - bought it new back on Nov 1,



    Recommendations for aftermarket plug brand (I might as well start
    there) ?

    Have never taken off a coil pack before - any special tools, or is it

    Which one is cylinder 2?
    MoPar Man, Oct 31, 2007
  2. MoPar Man

    maxpower Guest

    Start with replacing the plugs if you gonna take a pot shot at it. If it
    didn't take care of it the next thing you can do is swap coils from one
    cylinder to another to see if the misfire switches, if it does...replace the
    effected coil. you don't specify what engine, number 2 cyl on the 3.2/3.5 is
    on the drivers side front. the 2.7 is on the passenger side front.

    Glenn Beasley
    Chrysler Tech
    maxpower, Oct 31, 2007
  3. MoPar Man

    Bill Putney Guest

    Coil screw heads will either be torx #25 or #27 depending on engine.
    They can be frozen and difficult to remove without stripping the heads.
    Get torx bit straight and fully seated. Penetrating oil soak ahead of
    time wouldn't hurt. Also try good tap directly on head of the screw
    with a hammer to help break them loose before trying to remove.
    Glenn - Every piece of documentation I have says #1 cyl. is front
    passenger side for all three engines (3.2, 3.5, 2.7) and therefore #2 is
    front drive's side. Can you check your documentation and post back?

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Oct 31, 2007
  4. MoPar Man

    Bob Shuman Guest

    8 years on the original battery?

    Replace the battery since it is on borrowed time. A bad battery with low
    operating voltage can mess up the sensor readings and computer controls.
    I'd see how it runs after that before trying anything else.

    Bob Shuman, Oct 31, 2007
  5. MoPar Man

    maxpower Guest

    Your correct, I was thinking of the transverse set up as in a Sebring
    Convertible 2.7 which would put the #2 plug at the passenger side front.
    Must be an old age thing setting in
    maxpower, Oct 31, 2007
  6. MoPar Man

    MoPar Man Guest

    The coils came off easy, and so did the plugs.

    I started by putting a new plug into #2 (front driver side). Original
    plug was dirty (8 years, 72k miles). Replacement was exact same kind
    (champion). I didn't gap the new plug (do you still gap plugs these

    That didn't work - it still idled rough.

    I then replaced plug #1 (front passenger side) and swapped the coils
    between 1 and 2. (original plug 1 looked to be in the same shape as

    That didn't work - it still idled rough.

    Codes still say 1684 and 0302 (still indicating the problem is with
    cylinder 2).

    So at this point, how does the computer know that the problem is
    cylinder 2? What other sensor could tell the computer that #2 is the
    problem? If it was the injector, then why no injector codes?

    Regarding the battery -

    I did have to get a replacement ignition key and fob to replace a
    stolen one (about 2 weeks ago). The dealer reprogrammed the car to
    accept the new key and fob and reject the stolen ones. Would that
    have required disconnecting the battery?
    MoPar Man, Nov 1, 2007
  7. MoPar Man

    Bill Putney Guest

    Did you reset the codes?

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Nov 1, 2007
  8. MoPar Man

    MoPar Man Guest

    No - how do you do that?

    PS: Cylinder 2 is front driver side, with front meaning closest to
    the front of the car - yes?
    MoPar Man, Nov 1, 2007
  9. MoPar Man

    MoPar Man Guest

    Hypothetically, let's say my problem is a bad #2 coil. Say that's
    what's causing the 0302 code.

    So I swap coil #2 with coil #1.

    But I don't reset the codes.

    So I start the car, car idles rough, and the check engine light goes

    I then do another read of the codes.

    Because I didn't reset the codes, I guess I'll still see 0302. But if
    cylinder #1 now has the bad coil, shouldn't I now see code 0301 ???

    BTW, is there any way to reset the codes other than disconnecting the
    MoPar Man, Nov 1, 2007
  10. MoPar Man

    Mike Guest

    Yes. Plugs still get gapped unless they are platinum tipped.

    It may help if you replace all the plugs at that mileage.

    When the coil fires for cyl #2 the PCM expects to see a jump in cranshaft
    speed when cyl #2 fires. It reads crankshaft speed via the crank sensor. If
    cyl #2 doesn't fire the PCM sees no increase in crank speed and sets a code.
    It takes more than a single misfire to set a code.

    If it was an electrical problem with the injector the PCM would be able to
    pick that up and set a code. If it was a mechanical problem, such as a
    plugged injector, the PCM would not be able to sense that.
    Mike, Nov 1, 2007
  11. MoPar Man

    Mike Guest

    Yes, but it may not set a code for cyl#1 right away. You may have to run
    it for a while for the code to set.

    Yes, it can be done with a scan tool or some code readers. The easiest way
    to reset the codes is to diconnect the battery for a minute or two.

    I would suggest you leave the coils were they are now, replace all the
    spark plugs, clear the codes and take it for a ride and see if the check
    engine light comes on again.
    Mike, Nov 1, 2007
  12. MoPar Man

    Bill Putney Guest

    That's what I'm thinking. But also, if you reset the codes and you get
    no code later, but it still runs rough that would mean something
    different than resetting and getting the code for only cylinder 1. Not
    sure what exactly, but it would mean something. If code for cyl. 2
    comes back, that would be instructive too. Right now you don't know if
    it would come back or if you're just seeing the old code. I think we
    both suspect that cyl. 2 code will come back.

    Pull Fuse N in the Power Distribution Center for 15 minutes to reset the

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Nov 1, 2007
  13. MoPar Man

    MoPar Man Guest

    Resetting and getting no codes, and still running like a cylinder
    isin't functioning doesn't make sense, given the earlier code 0302.

    Do plugged injectors result in an injector code?

    Or does only an electrically-inoperative injector result in an
    injector code?
    Some references to the "Power Distribution Center" say it's located
    under the hood near the battery.

    I have no such item (that I can see) near the battery.

    I do have a "Fuse and relay center" on the driver's side, in front of
    the rad overflow tank. The fuses and relays are identified by name
    only - no numbers or letters. The relay center behind the dashboard
    panel on the driver's side are labelled with numbers - but I don't see
    anything referring to the PCM.

    So basically - where is the Fuse N you're talking about?
    MoPar Man, Nov 1, 2007
  14. MoPar Man

    maxpower Guest

    The fault code should have gone to the other cylinder if the coil was bad,
    you wouldn't have to reset the codes, it would have automatically set a hard
    fault code for the other cylinder if it were the coil. Your gonna have to go
    back to basics, compression? fuel (injector). The injector pintel could be
    bad or the injector is stopped up, this would not set a fault code unless
    the injector circuit was at fault. If you have the time, swap injectors.

    maxpower, Nov 1, 2007
  15. MoPar Man

    Bill Putney Guest

    I was suggesting resetting the codes first to maker sure cyl. 2 was not
    still having a problem that would set a code.

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Nov 1, 2007
  16. MoPar Man

    Bill Putney Guest

    Please tell me what references say that so I'll know to avoid them. :)

    Yep that's it.
    Here's a figure from the FSM that I have labeled the fuses on:

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Nov 1, 2007
  17. MoPar Man

    MoPar Man Guest

    To re-cap a little, my '00 300M abruptly started to run rough 2 days
    ago, obviously one cylinder wasn't working.

    I was seeing code P0302 on the odometer, indicating cylinder #2.

    I replaced the (original) plugs in both cyliners 1 and 2, but that
    didn't solve the problem.

    I swapped coils 1 and 2, started the engine a few times, but the
    problem was still there.

    I was expecting (hoping) to see code 0301 but it didn't show.

    Today, I drove the car about a mile, parked it, and then read the
    codes. Only then did it show both 0302 and 0301.

    I disconnected the negative cable from the firewall - I tried a few
    times but ultimately it had to be disconnected for between 30 to 45
    minutes for the codes to clear. I drove the car for a few miles, but
    it wasn't enough for the engine light to come on, or for any codes to

    I did a resistance check on the suspect coil and another (presumably
    good) coil and found that on the suspect coil there was a measurable
    resistance (less than 200 ohms) between the high-tension terminal and
    each of the primary (low-voltage) terminals. The "good" coil had no
    such resistance.

    I then bought a new coil at a dealership ($81 plus tax) and tested
    it. It also did not show any resistance between the high-tension
    terminal and the 2 low-voltage terminals.

    I installed the new coil and the other "good" coil and started the
    engine. It ran and idled smoothly.

    So the secondary (high-voltage) winding of the transformer had
    developed a short to the primary (low voltage) winding. The
    low-voltage winding measured about 1 ohm, but I wasn't able to measure
    the secondary winding because I couldn't figure out where to measure
    the opposite end of the coil (is it connected to the metal body of the

    I can see why it didn't generate a coil fault because the primary
    winding didn't fail (ie it didn't open up).

    Well, that was a relatively easy fix, not requiring any expensive
    tools, or any servicing at the dealership.
    MoPar Man, Nov 1, 2007
  18. MoPar Man

    Bill Putney Guest

    Just a little correction of your terminology: What you observed was
    "*low* resistance" (or high conductivity) between the secondary and primary.
    Again, you would say it didn't show any conduction... (or you could say
    it showed high, or "infinite", resistance...). Saying it "did not show
    any resistance..." technically means it was shorted, which I know you
    weren't meaning to say.
    Way to go! Sometimes an educated guess pays off.

    Reminds me of when I was in Navy electronics school over 35 years ago.
    They taught us troubleshooting methods. The book said to start where
    you have good signal, and move forward in the circuit with your
    troubleshooting equipment until you loose the signal. The point at
    which you lose it is where the problem is.

    So for one of our tests, they had these radios in the lab specially
    built for training purposes that they would put a bad part in, and we
    would have to find the bad part using the troubelshooting techniques we
    were taught. On a hunch, instead of starting at the front end and
    working my way to where the signal was lost, I sarted at the bad output
    end and worked my way backwards until the signal was good. Just so
    happens the bad part was very near the output end of things. So I
    finished the test in record time. Should have gotten a real high score,
    right? No! They gave me a failing grade because I worked my way
    backwards instead of the way we were taught. They didn't want people
    thinking outside the box. LOL!

    Anyway - glad you got it fixed.

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Nov 1, 2007
  19. MoPar Man

    bllsht Guest

    That would work if you were just clearing the codes using a scan tool.
    Clearing the codes by interrupting the power supply to the PCM will
    result in misfire monitoring being disabled. No misfire can be
    detected until the vehicle is driven under specific conditions to
    allow the PCM re-learn the baseline variance between cylinders.
    bllsht, Nov 2, 2007
  20. MoPar Man

    MoPar Man Guest

    (am I the only one to correctly edit their posts around here?)

    Jesus christ.

    Ok, that would explain a few things.

    Will this OBD II tool work for my '00 300M ?

    MoPar Man, Nov 2, 2007
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