Shared Knowledge

"BMW - Scan Tools"

31 Dec 2010


Summary: do-it-yourself (DIY) maintenance on a BMW automobile requires scanner capable of reading unique BMW diagnostic trouble codes (DTC) out of BMW's on-board computer and displaying real time sensor data. With a scanner, some but not all, DTC can be diagnosed and perhaps repaired DIY.



Original owner: BMW Z3, 2.8L, model year 1997. As of this date 50,000 miles.

Original owner: BMW X5, 4.4L, model year 2000. As of this date 145,000 miles.

In 2009, took over maintenance of both from dealer when quality of his repairs slipped.

Quickly learned that to do anything on a BMW, needed a on-board diagnostic II (OBDII) scan tool with the added capability to read unique BMW diagnostic trouble codes (DTC).

All modern cars are required to have an OBDII electrical interface (port). This standard interface provides information on the status of Environmental Protection Agency (EPA) required emissions control equipment, such as the oxygen sensors and catalytic converter. In the state of Virginia, in my city, emissions testing is required every 2 years and the testing station connects their equipment directly into the OBDII port.

On BMW, the standard OBDII port or connector is in the cabin somewhere behind a plastic cover and OBDII data is also available under the hood via BMW's enhanced diagnostic connector.

Beyond OBDII, BMW uses the on-board computer to control or monitor various devices such as antilock brakes, dynamic stability control, security systems, etc. When a device faults, it stores a DTC, unique to BMW, into the on-board computer. To read BMW unique DTC's, one needs a scanner specifically for a BMW.


Peake Scan tool:

One of the more popular OBDII scanners for BMW, this scanner plugs into the BMW enhanced connector under the hood or into the OBDII standard connector in the cabin. It has no batteries and needs no other connections to car. It will display various DTC's out of the on-board computer in a 2 character LCD display and allows reset of the oil change service bars as well as the "Check Engine" light. BUT, although it does read fault codes, it provides no information as to what a fault code means and I have discovered it misses fault codes. It also has no ability to read any sort of real time sensor data such as oxygen sensor voltage or mass air flow voltage. Also, it has no ability to read the CANbus, which is used by BMW to communicate and control various devices such as the antilock brakes. The Peake OBDII scanner also can not reset the airbag malfunction light. Another Peake tool is required to reset to reset this light.

So, my take on Peake is: it is convenient as you simply plug it in and press 2 buttons and if you only need to reset the oil change service bars this scanner will work fine. Think I paid about $100 for the scanner and as I had to have an airbag reset tool, another $100 or about $200 total.

Unfortunately, various problems can be impossible to try to diagnosis and solve using the Peake tool. For example, if your "Check Engine" light is on all the time and comes on again after being reset by the Peake tool, you have no way to see sensor valves related to emissions control and thus "Check Engine" light. Or if you have an antilock brake or dynamic stability control (DSC) problem, Peake will not help at all.


Genetic handheld scanner:

There are many hand held OBDII scanners available and some of these have the ability for you to actually see real time sensor data such as oxygen sensor voltages but I do not know of one that can handle BMW unique DTC's. Auto Zone will lend you a handheld scanner that plugs into the OBDII port in the cabin but the time I tried using an Auto Zone scanner, so many settings, options, etc. that without first reading the thick instruction book, would be near impossible to use and gleam any useful information. And again, these devices do not deal with BMW unique DTC's.


AutoEnginuity personal computer (PC)-based scanner:

AutoEnginuity makes a PC-based scan tool that connects a PC to the BMW via the OBDII or the BMW enhanced connector. (There is also a wireless option). The base software only reads ODBII information but can display in real-time data for: oxygen sensors, mass air flow (MAF), and other emissions related components. This is absolutely required to solve a persistent "Check Engine Light". For other BMW specific components, an additional software module must be bought. This module reads the CANBus so you can see wheels speed sensors, antilock brake error codes, etc. Autoenginuity can clear all stored DTC's, reset oil service light and clear the airbag light. At close to $500 for the base plus the BMW specific software module, AutoEnginuity is not cheap but it is mandatory or something like it to be able to diagnosis and repair difficult problems on the BMW.

Shows O2 sensor, pre and post catalytic converter voltages over time

Above shows real time data of both pre and post oxygen sensor voltages as shown on laptop hosting Autoenginuity BMW scanner software.


BMW scanners on eBay:

If you search eBay, you will find many BMW scanners for sale. Most, if not all, come out of China. Most, if not all, are relatively cheap. As I have never used one, can not testify to how well they work. I suspect all are a clone of some other scanner.


Personal scanner limitations:

All personal, meaning relatively cheap, scanners have limitations. There are devices, the DSC module being one, that has to be registered or "coded" for your specific BMW. No personal scan tool will do this. The scanner at some independent repair facilities can code BMW devices while others can not. Thus there will be times that although you can diagnosis the problem with your personal scanner and maybe procure a cheap replacement part, you then face the problem of getting someone to code it for you.

Independent automobile repair facilities than repair BMW's have scanners that cost multiple $0000's of dollars to procure and then update and these scanners have greater diagnositic ability than you or I can afford.

Beyond the capabilities of the scanner available to independent repair facilities is the scanner at a BMW dealership.

A personal scanner will help with many situations but there are times you are going to have to use an independent repair facility or a dealership.