Error Code P0305

Okay, after about 2 months of not driving my Z4 because it started to spunder/rough idle, I took it out this holiday weekend to check out, and the code I got back was P0305, here is what I found on the net:


It seems to say that there are generally 4 possibilities in case of a P0305 (or any P030x) cylinder misfire:

1. - sparkplugs
2. - plug wires/boots
3. - ignition coil
4. - fuel injector


Now, from reading from other forums, #1 it seems this is very common, #2 it a game of trail and error finding out what could be the cause, spark, wires, coils etc... I am just wondering if anyone else had this problem before and how did you fix it?

Thanks

It's a misfire in cylinder No. 5.

Your car has no wires or boots.

My guess (and I bet I'm 99% right) is it's the coil for that cylinder.

I'm in the midst of solving one right now. I got a P0306 code. I figure it is most likely the ignition coil, considering BMW already has had one recall to replace the coils on some of the Z4's.

My first step has been to switch the cylinder 6 and cylinder 5 coils and reset the code. So far the code has not come back, but if it comes back as a P0305 (cylinder 5), then I know it is almost certainly the coil causing the problem.

Note that since the Z4 engine uses a "coil above the plug" system, it is extremely unlikely that the plug wires are the problem -- the wires no longer carry high voltage, as in the older style systems, and rarely fail or deteriorate.

Now, on a BMW there is another likely reason you can easily check. Often the valve cover gasket can develop a leak, and sometimes it will result in the spark plug cavity filling with oil, causing a misfire. This is rather easy to check, as if the spark plug cavity is filled with oil, that's the problem.

My Z4 did the same thing a few years back, didn't think I would make it to the dealer. The ignition coils were the problem and once replaced, (under warranty), problem solved. BMW knows too well that there were problems with the coils and should replace them with no questions asked.

This was just posted on another forum. Maybe it will help.


The issue was with the Bremi coils, which may have not made it into the Z4M series. I have read on this forum, regarding a Z4, with a hesitation and new(er) coil packs being installed by the dealer, although it did not resolve the problem.

Here is the old SIB:

This Service Information bulletin supersedes S.I. B12 08 03 dated November 2003.
designates changes to this revision
SUBJECT
Bremi Ignition Coil Replacement
MODEL
E36/7; M roadster/coupe with S54 from 02/01 up to 06/02
E46, M3 with S54 from 03/01 up to 11/02, and from 01/03 up to 07/03
E46 with M54 from 09/02 up to 11/02, and from 01/03 up to 07/03
E39 with M54 from 09/02 up to 11/02, and from 01/03 up to 07/03
E53, X5 3.0 from 09/02 up to 11/02, and from 01/03 up to 07/03
E85, Z4 from series introduction up to 11/02, and from 01/03 up to 07/03
SITUATION
Engine may run rough and "Check Engine" light is illuminated. Misfire faults are stored in DME control module.
CAUSE
Reduced ignition firing power of BREMI coils due to coil internal insulation deterioration.
CORRECTION
Follow the appropriate Test Plan from DIS Plus/GT1.
If BREMI ignition coil is found to be defective, and the production date stamped on top of other coils housing's is
42/2002 or earlier, or in the range from 01/03 up to 24/03 all six coils must be replaced . For replacement instructions
refer to RA 12 13 511 found in BMW TIS.
Only coils manufactured by BREMI are affected. BREMI coils are easily recognizable by the all black, shiny housings.
Bosch coils, which can also be fitted in M roadster/coupe and M3 vehicles with S54 engines, are not affected and should
NOT be replaced as a set. Bosch coils have a silver, aluminum housing.
SI B 12 08 03
Engine Electrical
February 2004
Service Engineering
The last four digits stamped on the top of
BREMI ignition coil housing indicate
the calendar week and year of
production.
As shown on illustration: Week 42 of
2002
PARTS INFORMATION
WARRANTY INFORMATION
Covered under the terms of the BMW New Vehicle Limited Warranty.
Note:The following explanations will spell out the correct use of the work times.
Part Number Description Quantity
12 13 1 712 223 BREMI ignition coil Maximum of 6
Defect Code 12 13 91 12 00
Labor Operation: Labor Allowance:
Main Work 00 54 124 11 FRU – E46, M3 with S54
8 FRU – E36/7, M roadster/coupe with S54
7 FRU – E85, Z4 with M54
9 FRU – E39 with M54
7 FRU – E46 with M54
7 FRU – E53 X5 with M54
+ Associated Work 00 54 692 9 FRU – E46, M3 with S54
6 FRU – E36/7, M roadster/coupe with S54
6 FRU – E85 with M54
6 FRU – E39 with M54
7 FRU – E46 with M54
5 FRU – E53 X5 with M54
Main Work: Use this labor operation number when the only repair performed is the
listed warranty repair.
OR
+Associated
Work:
Use this labor operation number when other repairs or services are
performed along with the listed warranty repair.
Under no circumstances should both labor operation numbers be claimed.
Attempts to claim both times will result in an unnecessary delay in claim
processing and payment.
[ Copyright © 2004 BMW of North America, LLC ]

OK, after switching the two coils around o help in diagnosing the problem, I have driven more than 500 miles with no code thrown.

Since a coil is physically small and only about $30, I bought a spare and stuck it in the trunk. If the code returns, I'll swap the new coil in. But otherwise, I'll assume the code was a temporary random misfire issue from sitting around too long between engine starts.

I had to have one coil replaced and was not aware of the SIB. So I now have 5 more BREMI coils which could act up at any time. Mine is an early '03 so it falls in the SIB range. Now the question is will the dealer replace the other five for free even after 80K miles?

>> Now the question is will the dealer replace the other five for free even after 80K miles?


Probably, if it meets the conditions in the service bulletin. Ask your dealer to run your VIN in their system to see if it pops up. Mine were replaced without request, as part of the normal check they did when I had the oil changed.

Here's a thread with the number:

http://bimmer.roadfly.com/bmw/forums/e85/7206613-1.html

05E-A01

If you have a good relationship with a dealer, they can probably get BMW to approval replacement of the coils for free. If you don't have a relationship, and bounce from dealer to dealer to save a few bucks, perhaps not.

When I was in the industry the costs associated with this were called W&P, Warranty and Policy, The warranty part was what the company was obligated to do, the policy part was what the company did, usually on a case by case basis, to keep loyal customers happy.