Which BMW E90 Diagnostic Tool Is Best?


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Are you the owner of an E90 BMW 3 Series? Are you interested in learning more about your vehicle? Do you wish to save money, run vehicle diagnostics by yourself, or even personalize certain aspects of your car? You don’t need to drop everything and drive to a workshop every time a warning light illuminates. You can simply purchase a BMW E90 diagnostic tool and do it all yourself. There is a broad market for diagnostic devices, and we want to help you choose the best one for your BMW E90 in this article.

Which is the right BMW E90 diagnostic tool for your car? There’s a large selection of devices that can cater to your BMW E90 at various levels, and therefore costs may vary. For example, you might find a decent scanner that enables you to read out error codes for as little as €30, as well as professional-level devices with a vast array of functions that cost thousands of euros. A great and cost-effective option is the Carly app and Carly Scanner. The Carly app costs between €21 and €80 per year, and the Carly Universal OBD Scanner costs €59.90 (a one-time purchase).

This article will give you a deeper insight and show you what to look out for when buying a diagnostic device for your BMW E90.

Basic Knowledge

Before we dive into recommending a BMW E90 diagnostic tool, let’s go back to basics in order to help you understand the components of vehicle diagnosis. If this is something you already know, feel free to jump straight into the next section.

Types of Diagnostic Equipment

In order to be able to carry out a vehicle diagnosis, you need the appropriate diagnostic equipment. There are three different types on the market. There are external standalone diagnostic devices, software for laptops, and apps for smartphones. Each of these types has its advantages and disadvantages. From our perspective, the smartphone app is the best solution, with a vast array of benefits that far outweigh the relatively few disadvantages.

External diagnostic devices typically come with a small screen and are suitable for simple diagnoses, unless you opt for a workshop-level device that costs thousands of euros, but with that, you give up portability. Portable external diagnostic machines can be very cheap, but offer limited functionality, with small screens that only display error codes. You then need to do a lot of Googling to determine what the codes actually mean. Furthermore, if you frequently travel and desire to keep your device with you on the road, you have to carry it with you. That’s one more thing to keep track of.

Software for a laptop is also largely impractical for your average car owner or even car enthusiast, as it necessitates you to carry your computer and the associated adapter cable around with you. Furthermore, software for a laptop needs to be purchased and may not be regularly updated. Finally, even if it is updated, there is a decent chance that you would need to pay for the update, adding to the overall costs of the solution over time. However, the software for laptops can offer comprehensive diagnostic solutions, and the large screen of the computer can display a lot of data.

Overall, smartphone apps are by far the most practical. You always take your smartphone with you, after all. Smartphone apps are user-friendly, can offer a vast array of functions, and, best of all, tend to be regularly updated for free. Our unequivocal recommendation is the Carly app. Apart from comprehensive diagnosis, Carly offers a plethora of functions that we will describe to you further into this article.

Error Codes

Dozens or even hundreds of control units are built into every vehicle. Each is responsible for a different system. Fixed parameters are entered in these control units within the framework of which the connected systems should work. If there are deviations, error codes are generated and saved. There are tens of thousands of error codes, known as DTC (Data Trouble Codes), and of two different types. There are internationally standardized codes and manufacturer-specific ones. Practically all diagnostic devices mentioned can read the general error codes, but only the scanners and smartphone apps that are specialized for individual manufacturers can also understand the manufacturer-specific error codes.

However, all codes have the same structure. They consist of 5 characters. The first character refers to the rough area in which an error has occurred. B stands for body / C for chassis / P for powertrain (drive, engine, and transmission) and U for the network (OBD interface). With the second character, you can see whether it is a standard error (“1”) or a manufacturer-specific error code (“2”). At the third character is digits 1 to 8, which describe the affected system in more detail. Finally, the 4th and 5th character (digits 00 to 99) indicate the actual error.

The simple diagnostic devices show you the raw error code, such as P1588 or U0463, for example. Then you have to do some research on the internet to find out what these codes mean, as well as what could cause them and what must be rectified. Better devices also give you a description. The best apps, such as Carly, actually evaluate the errors and inform you which ones are of utmost importance, which ones can be rectified later, and even which you can safely ignore.

Control Units

Each control unit is its own small computer and is responsible for a single system in the vehicle. For example, one control unit controls the air conditioning, another controls the engine, and so on. Therefore, there are dozens or even hundreds of them in the vehicle. The control units, the connected systems, and the OBD2 interface are all connected to one another via a data highway that is the communications backbone of the car.

In most cases, deviations from the stored specifications in the control units are regulated directly by these, and the connected systems can continue to work. An error code is generated, but it is of very little relevance. However, if there are major deviations that cannot be internally regulated, the driver may be warned, or a significant error may be generated. The Carly app evaluates the error codes and shows you the most important ones in descending order. You will also receive a vehicle health report, but more on that later.

OBD2 Interface

The aforementioned OBD2 interface is accessed via a socket that is located beneath the dash of your BMW E90 to the left of the brake pedal. This interface is used to connect an external diagnostic device to the vehicle. It would be best to have a decent OBD2 scanner to ensure proper communication, as poorly designed ones can misinterpret errors or even cause damage to the control units. With this scanner, the commands are translated into a language that the vehicle can understand. If you are using an external diagnostic device or software on a laptop, the connection is typically by cable. An OBD2 device such as the Carly 20-pin scanner is used when using a mobile app, which connects wirelessly to the smart device. Technologies used for connection are usually Bluetooth or WiFi. The scanner can always remain in the socket if desired, as in the case of real-time monitoring, or it can be stored away in the glove box or similar compartment.

For those of you who would like to know more: OBD is the abbreviation for on-board diagnostics. This standard was developed over 40 years ago in the USA in order to monitor all emission-related values of a vehicle. To protect the environment, the driver should be notified if, for example, the exhaust gas values are too high. However, it remains up to the driver to decide whether to change something or not. This will change with the OBD3 standard that is currently under development. With this new standard, faults in the exhaust systems are reported directly to the responsible authorities via SIM card or satellite. In such cases, the driver may have to have the system repaired within a certain period, otherwise, penalties could be imposed. It is, as yet, undecided whether this new standard will also be introduced in Europe, and if so, it could be some time before it becomes mandatory.

The CAN-Bus (For the Nerds among You)

We talked about the information superhighway above. A CAN bus system is used in a vehicle. Data “buses” constantly drive from station to station on the data highway and take data packets with them if they are available. For example, if you create a new setting in the app, this command is transmitted to the OBD2 adapter via BLE (Bluetooth low energy). The ELM 27 chip inside translates the command into a language that the vehicle can understand. The data is then transferred from the OBD2 socket to the relevant control unit via the data bus and implemented there. Confirmation is, in turn, brought back to the interface in the form of a data package by bus, translated, and transmitted wirelessly to the app. All of this happens within a fraction of a second, giving the feeling of receiving confirmation of the change almost immediately after entering it.

What Does a Vehicle Diagnosis Do?

If we consider actual vehicle diagnosis, it pertains to reading out and analyzing fault codes. The simple and inexpensive devices — such as a cheap BMW E90 diagnostic tool — can only read out the codes and present them in code form. Some can also delete codes, but nothing more. When using one of these devices, understanding each readout will require online research. Better options will give you a description in plain, understandable text as to what the error code refers to.

B0115 means, for example, that a short circuit has occurred in the area of the side airbag lines (controlled by the SRS control unit). Some simple diagnostic devices only show B0115. Perhaps a better device will display “B0115: Side airbag lines short circuit.” With the best diagnostic tools, you will not only receive a description, but an indication of the severity of the error and whether you must immediately address it, deal with it later, or disregard it.

bmw e90 diagnostic device which is the best

What Are the Costs of a Diagnosis?

There are two kinds of costs pertaining to diagnosis. One is the direct cost of diagnosis, and the other is the costs that can be saved if any errors are detected early and their relevant fault conditions corrected before they become serious problems.

A simple vehicle diagnosis in a workshop costs between €25 and €60, depending on the model, manufacturer, and workshop. Therefore, with a regime of one diagnosis per quarter, you’ll spend about €160 if it costs an average of €40 per visit. In addition, there are costs and effort for scheduling, the time for bringing and collecting the vehicle, and additional transport costs if you need to do stuff while your car is in the shop.

The Carly app is available for around €6 a month for your BMW E90. In addition, there is a one-time purchase of the Carly Universal OBD Scanner of €59.90. A decent external adapter such as the Carly scanner is a necessity for all external diagnostics, including any BMW E90 diagnostic tool. The price includes the entire range of functions of the Carly app. Additional direct costs of hundreds of euros can be saved here. Find out more about this at the end of this article.

The secondary costs saved can hardly be quantified, but they are certainly in the range of several hundred or even thousands of euros per year. You can run a diagnosis as regularly as you wish, even once or twice a month. So, you can identify minor errors and underlying problems and correct them before they compound and result in significant, expensive repair, all thanks to a good BMW E90 diagnostic tool.

Which BMW E90 Diagnostic Tool Is Best for You?

We’re here to convice you that your best option is the Carly app. It offers a range of additional functions that we will shortly get into, is available for download from the Apple App Store and Google Play store. The Carly app has already been downloaded over 1 million times, and you can get started with the free version of the app, which allows you to trial a limited but still impressive array of functions. These are the most essential functions of the Carly app.

Vehicle Diagnosis and Health Status

The Carly app can not only read and understand standard error codes but the manufacturer-specific ones pertaining to BMW and the BMW E90 as well. The Carly BMW E90 diagnostic tool won’t leave you in the dark but will give detailed explanations of the detected error. But wait, there’s more. Carly goes a step further by providing you with the health status of your vehicle by evaluating faults according to their severity. A traffic light system is used — if your car gets a green light, it’s healthy, and you don’t need to do anything. If an orange light is displayed, you should perform a further diagnosis as there are errors that need attention, and if a red light shows, your car is seriously “sick” and requires immediate action.


Coding sounds technical, doesn’t it? Well, it doesn’t have to be. It’s about setting your personal preferences for many functions in your BMW E90. You can set various parameters pertaining to a myriad of areas, including cornering lights, indicators, brake lights, Corona Rings, convenience functions, Parking Sensors (PDC), Entry Aid, electric windows, Powered Tailgate, Welcome Home Lights, climate control, Engine Start/Stop and much more. There can be hundreds of things and ways to customize. If you were to do this in a workshop, each individual setting would cost between €30–€50, but with Carly, you can do as many as you like, trying out different settings and changing between them.

Carly Used Car Check — A Lifesaver

Only Carly has this function! If you are buying a used car, such as a BMW E90, the greatest difficulty is in finding a good one. Unfortunately, even the best-looking car may have had its mileage tampered with. Mileage tampering is a serious issue, and statistics show that up to a third of used cars may suffer from it. The Carly Used Car Check is a unique feature that queries all relevant control units and can identify evidence of mileage tampering, displaying a report on this. You can then determine if the seller is reliable or not and save thousands of euros, all via our BMW E90 diagnostic tool!

Service Reset

There are some activities that the enthusiast owner can handle, such as changing the oil (read below to know what you should be aware of with this task). After changing the oil, you need to update the control units and reset the service interval so that the system knows that the oil has been changed and will not continue to display service warnings. Carly can do this easily for you. You can also register a new battery or perform other services yourself with Carly’s help, saving money once again.

A Slight Digression: Changing the Oil Yourself

Oil change intervals vary, between 15,000–60,000 km. You can easily change the oil yourself, but you must pay attention to a few things. First, ensure you are using high-quality oil that complies with the manufacturer’s specifications. It would help if you also had a way to elevate your vehicle, as well as a tray to capture the used oil — spilling it on the floor where it can seep in is an environmental disaster. It’s best that you do this at an appropriately equipped DIY workshop. Incidentally, the seller of new oil must take back your used oil, free of charge; otherwise, you can recycle it at a properly equipped recycling center. Never pour it down the drain or with household rubbish under any circumstances.

Retrieve Vehicle Data in Real-Time

Would you like to monitor parameters such as fuel consumption, exact road speed, oil temperature, or other values in real-time while driving? Carly offers a real-time function that allows you to do this. You simply bring up the corresponding parameter and can monitor it.

More Functions

In addition to the functions mentioned, there are many more such as emissions tests, the reset of the automatic transmission, the digital garage (here you can save all values and save or forward them as PDF or by email), checking of the diesel particulate filter and so on.

Simply download the Carly lite version for free in advance and see what is possible with your model.

bmw e90 encode what can you do

Goodbye Workshop?

So, is it a goodbye to the workshop? Unfortunately, no. It’s true, you can reduce your workshop visits and associated costs by using Carly, but they cannot be avoided entirely. No app can do this. There will always be minor and major repairs that must be carried out by a workshop, as well as complex problems that a specialist can only recognize. However, you can carry out the minor diagnostics, coding, and service resets yourself, for example, saving time and money.

A Final Summary

After reading this article on which diagnostic device is best for your BMW E90, we hope we have shown you that the Carly app is an ideal solution. From now on, you can read out error codes, carry out simple maintenance work, optimize your fuel consumption by observing live parameters, code your car to your liking, and more. All this is rewarding, but most of all will help you save hundreds or even thousands of euros in the process. Your expectations will definitely be exceeded.

Keep in mind, that every car has different software and modules built-in. Therefore specific features will vary with every model.

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