BMW dealer does not understand standardised OBD fault codes!?

My car is now due for its oil service and so I thought this might be a good time to seek some professional input on the error code P3263. I use a BMW dealership because they've treated me well in the past and my hope is that they know as much, if not more, than anyone else. Unfortunately to my surprise they informed me that the OBD fault codes obtained from my ELM device are meaningless to them! The 'official' BMW diagnostic tools access another set of codes! So I have two choices. To put my faith in the dealership to efficiently solve the problem or continue investigation. Having read several horror stories of people spending hundreds of pounds at garages and the same fault re occurring soon afterwards I favour some further investigation.

To this end I've been studying more about MAF meters, EGR valves, turbo boost control and how that relates to volumetric efficiencies and fuel metering! The tool I've been using is my bluetooth ELM327 interface and Torque app on my Samsung phone. It has allowed me to log these parameters to a spreadsheet  in order to try and analyse what may or may not be happening. The results are interesting but it's still difficult to draw a conclusion without the benefit of a set of results for a 'healthy' engine. One thing it is easy to see is that the EGR valve is working following it's de-coke. Disconnecting the vacuum pipe that opens and closes the EGR causes the results to change dramatically. It also causes black smoke from the exhaust when revved. A common sight from a diesel but something I guess has more than one reason.

More later as I look more closely at the figures or take the plunge and buy a new MAF meter.

MIL On

One reason for this blog was the periodic illumination of the MIL (Malfuncion Indicator Light) on my car. Having read so many horror stories of the cost of professional diagnosis I wondered if it was within my capabilities to diagnose the cause.

Using my OBD adapter and the free Torque app for my mobile phone it was easy enough to obtain the information code being reported by the engine management computer. It was (still is) P3263. The P means the code has been generated by the Powertrain module i.e. engine control unit (ECU) rather than air bag unit etc. More about these OBD codes can be found here. However, whereas the meaning of these codes are often common to all cars and publicly available mine starts with a 3 meaning manufacturer specific! Unfortunately, it seems manufacturers still guard sets of these codes closely and so create or rather hold on to the car owners dependency on the dealer or specialist. (Although they may say the codes should only be interpreted or acted upon by personnel with specialist training).

After much, much searching the best interpretation was relating to the measurement of air flow going into the engine. More accurately a problem with the calculated amount of air compared to the measured amount and this has started a whole new chapter in learning about how the ECU uses the mass airflow meter (MAF) meter, turbo and exhaust gas recirculation valve (EGR). A very steep learning curve but I'm getting there!

To finish this post on a positive note the first part of my investigation and remedial work was to clean the EGR valve. The result was about 8 miles per gallon better fuel consumption! More on EGR's etc later.

Genuine ELM or Clone OBDII Adaptors

The device shown in the previous post is a clever piece of electronics that itself is a small computer. One that is dedicated to working out what standard the car is using and then presenting a standard interface to the computer. If I understand correctly this device was first introduced by a company called ELM and a fantastic concept and product it is. Without it the OBDII interface would still be inaccessible to a home enthusiast like myself.

When I purchased my interface I was unaware of the history and then discovered that, as far as I understand, it is a clone of the first version of the genuine ELM product. Like thousands of others I was attracted by the price but ignorant that it is a copy. It would seem the first versions had not been copy protected like subsequent versions. So whilst the official product continues to develop and address bugs etc the clones probably don't.

The adaptor I purchased did work successfully (although one did fail after a couple of months) but perhaps problems may be experienced in due course. Speed is one reported issue. The ability to interrogate the car fast enough. Reliability as I have found is another.

Some of the current low cost adaptors boast being version 1.5 but from what I have read there isn't currently a version 1.5 from ELM, the architects of the product. The version is therefore misleading and probably refers to the physical package and not the functional operation.

Connecting to the Management Socket

Communicating with the car management requires a cable (or optionally a virtual cable such as a Bluetooth connection) and, of course, a computer. However, there are a few concepts to understand that may help with general understanding of what's happening and the purchase of equipment.

Communication between a computer and a car requires a whole range of things to be compatible. It starts with the function of each pin on the connector, includes voltage and timing of signals through to the more human understandable commands and response codes. For example, the most basic part of the standard, but non the less important, is the physical design of the plug. A standard computer doesn't have one of these so that demands some form of physical adaptor.

Unfortunately, there are a number of different standards in use by car manufacturers that affect the operation of the interface. Fortunately, the connector specification is the same but to work out the rest requires an intelligent piece of electronics to mediate between the car and computer. Shown below is a device I purchased to do the job. But more on this next!

The Management Socket

This is a picture taken from the drivers side door looking up under the steering wheel in my Peugeot 206. The OBDII management socket is with the fuses etc and is the green component on the right.

A Network of Computers

Until recently my understanding had been that there was only one computer on a car and that was the Engine Control Unit. However, it appears that this is not necessarily the case. Some cars may have more and this is an important concept to know when communicating with the car (The airbag system may be one and perhaps the ABS system another and of course there is the locking system etc).

These computers share what is known as a bus and is the connection by which they talk to each other. The communication standard does appear to have evolved over the years but the predominant one now in use would seem to be the CANBUS. The CAN standing for Controller Area Network. (It's quite a revelation to think my car includes a computer network)! This concept of a network of computers (more accurately called controllers because they are computers dedicated to certain tasks) becomes important when understanding the language used for managing the CANBUS.

Standards and the OBDII interface.

Around about 2000 something important happened. The various standards organisations around the world introduced standard for communicating with car computers. Prior to this cars had been using computerised systems but all required their own specialised service equipment. The introduction of standards meant that the same service system could be used on a BMW as a Ford or Peugeot etc.

The standards have been phased in over a period of time so it depends on a cars age (manufactuter, country...) as to whether it has the standardised facilities. In europe, for petrol cars, it was around 2000. For diesel the standards appeared later in 2004-ish.

One part of the standards was where the socket to connect to the car should be sited. This is within 1m of the driver. On one of my cars its in the footwell. On another its in the centre console (hidden but easily accessible under the ashtray unit).

The socket is the OBDII interface and looks like a SCART socket found on most televisions.