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

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
website:

http://www.aa1car.com/library/copign.htm

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
plugs).

Car is exactly 8 years old tommorrow - bought it new back on Nov 1,
1999.

Comments?

Answers?

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
self-evident?

Which one is cylinder 2?

 

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

 

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')

 

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

 

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

 

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
days?).

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
#2).

That didn't work - it still idled rough.

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

3.5L

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?

 

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')

 

No - how do you do that?

PS: Cylinder 2 is front driver side, with front meaning closest to
the front of the car - yes?

 

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
on.

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
battery?

 

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.

 

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.

 

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
PCM.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

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?

 

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.

Glenn

 

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')

 

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:
http://images22.fotki.com/v810/photos/4/42816/1994050/PDC1999labeled-vi.jpg

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

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
appear.

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
transformer?).

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.

 

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')

 

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.

 

(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 ?

http://www.redflagdeals.com/deals/main.php/alldeals/comments/princess_auto_obd_ii_code_reader_4999