’02 Factory Diagnostic Plug – What’s that for?


BMW 2002 Series – Factory Diagnostic Plug

Have you ever seen this plug on your fender near the fuse box, and wondered what it did?  Well BMW had the best intentions to maintain the car with it.

As shown in the photos from the original 1974 era sales brochure, BMW had their own diagnostic system to read the car’s systems and conduct service.  Fortunately in today’s world you can do this with an inexpensive hand held automotive multi-tester unit.

With that in mind, here’s the diagram you want. You can use this for your own needs in diagnosing and maintaining the car.  If you’re handy with a volt meter and electronics, you have a new project!

The ’02 Guy’s Bookshelf


After 30 years it’s not surprising to find out that only a handful of books exist for 2002 owners outside the BMW camp of knowledge. As they say, ” knowledge is a power” — so tune up your brain first, then you car by reading and learning 2002s through these publications. Experience has shown these books will save you both time and money in the long run. So… In our opinion, buy the 4 books below in this order 1-4. The other book not mentioned, which is perhaps the “ultimate 02 book” is the original 2 volume hard copy of the BMW 2002 factory shop manuals if you can find them in good condition. The CD-Rom versions are available but not as clear as the originals. 1. BMW ’02 Restoration Guide
(Amazon Link to buy)
Mike Macartney, owner and co-founder of Jaymic, the premier restoration shop for 2002’s in the UK, wrote this book as the follow on to book #3 below. There is some carry over content from that book that is history related, but 90% of this book is great content for any 2002 owner. The author sometimes stops short of the complete subject at hand, which is unfortunate, but sometimes intended. When you are in the restoration business, why give it all away? This book has more practical 2002 know how than existed prior to the internet. A must for anybody contemplating a mild to wild restoration. 2. Hayne’s Automotive Repair Manual – BMW 1602 and 2002
(Amazon Link to Buy)
The Haynes book is the cheap copy of the 2002 BMW Shop Manual. Many of it’s figures, photos and diagrams were lifted directly from the factory shop manual. Contains a lot of the “Queen’s English” terminology when referring to the car, as you would expect from authors in the UK. 3. BMW 2002: A Comprehensive Guide to the Classic Sporting Saloon
(Amazon Link to Buy) This was Mike Macartney’s first book about 2002s. It’s a great one to keep in your car to show people what you mean when they start asking questions and referring to ’02 models you know don’t exist. 4. BMW 2002 Ultimate Portfolio 1968-1976
(Amazon Link to Buy) This is Bentley Books’ reprint of many of the press, factory brochures and auto trade information about the ’02 family of cars. Great for looking at the reviews when the cars were new by the great authors of the time.

SEE ALSO – (Books to search for …)

Out of print The CLYMER book BMW Service Repair Handbook, is long out of print. You may find it at a swap meet or used book store. The diagrams and photos are very clear, and is a smaller sized version of the Haynes without a lot of fuss. Much of what is here was written prior to the 2002tii model, so there isn’t much in the way of fuel injection, but is a wealth of knowledge, even on side draft Solex PHH40s, for the carb owners. There is also an interesting section on hi-performance modifications and discusses the equipment available of the day for that type of modification. I find this book a great one to keep in the car for trips when that roadside repair pops up. BMW 02 Series – The Cult Car was published by BMW in the year 2000. It was a limited edition printing and has been out of print for some time also. They have become prized possessions of those lucky to land a copy before they were gone. It was developed and produced by BMW around the year 2002. It sold for around $50 originally, and was worth every penny. Despite a wealth of history, folklore and wonderful photographs from the BMW Archives, it even includes a reproduction of the original BMW 2002 Turbo brochure.

Troubleshooting the Smell of Gas Fumes



My 73 trunk smells like gas – not overpowering but enough to be noticed when the lid is opened. Is the small plastic vent line that penetrates the filler tube routed outside the car? All hose clamps are present, hoses look like they have been replaced and the pickup plate screws are secure to the tank. Any ideas?

The best solution to solving gas smell is a process of elimination.

In the photo below, the red arrow shows where the fuel pipe exits the trunk on most 2002s built from 1968-1973. We say some, because it’s not exactly clear if some USA round tail light cars had the later model charcoal vapor container which were mounted above the right rear wheel housing in the trunk.

If you have a bracket above your right rear wheel housing mounted to the package tray, chances are your tank vents to it instead. The 73 2002tii in the USA was a crossover year model which has some variations between old and new because of engineering changes which occured during that build year in preparation for the later 1974-1976 cars.


The red arrow below shows where on the early cars it vented through the floor to the exterior of the car.

On cars with the grey plastic charcoal vent container, the line connects from the rubber fuel neck inside the trunk and follows along the wheel housing to vapor canister.


The 2002 fuel tank is made of two pieces of steel put together. They are notorious for rust right at the seams where it was put together because of a foam seal underneath the tank which the factory used to stop vibration. This seal was porous and held water, so the rusted severely around the tank in climates where moisture was common. This rust can lead to severe structural integrity problems.


Most 2002 fuel tanks are no longer available and if they are run more than $600 new. At the time of this writing, 2002tii fuel tanks are no longer available.

It is a good idea if you plan to keep your car and make it reliable is to put all fuel tank fume and leak mysteries a thing of the past.

  • Drain the fuel from the tank itself from the car. There is a small allen head drain plug near the bottom front of the tank under the car which makes it easier.
  • Remove the tank (5 black arrows in photo above). Check for rust on the car where the tank sits inside the trunk and repair if necessary.
  • If you have rust, likely you have tank edge separation. Check the edges of the tank closely for problems.
  • Seal your tank with a proven fuel tank sealer, such as POR-15 or Eastwood makes. Follow their directions.
  • Have your fuel tank boiled out by a radiator shop. The 02 tanks are small enough most shops (unless environmental laws prevent it) will do this for you.
  • Once the inside is done, the edges are next. POR-15’s putty can be used to seal edges where the metal has begun to separate. JB Weld can also be used for this also.
  • Use a high quality undercoating such as 3M in a spray for the underside of the tank, and a good rust preventative black paint on top.
  • Replace your fuel lines with genuine BMW high pressure fuel line materials. They are cheap insurance against fire and clogged fuel filters which can occur after 30 year old hoses have not been replaced.
  • Mount back in your trunk with Stainless Steel fasteners instead of the original Zinc type to prevent further rust issues (See black arrows above)
  • Last, check your trunk seal and make sure it’s in good repair.

Another note… If you have speakers in your trunk, they also may be pumping the fumes into your car also, however finding and curing the leaks and the source of the fumes normally rids your car of future smells.

Last update: 2007-08-14 19:09
Author: The Tii Register