CBS (condition based service); is a service system developed by BMW to have a vehicle decide for itself when service is due. This post will go through how the system works and what and how a vehicle decides services.
The CBS data is different from car to car. For example, an M vehicle will have more items serviceable than a non M car. All this data is stored in the vehicle and can be viewed to give you a basic idea of what’s due. This is only a basic view and does not show all of the included services. More on this later.
The best way to see your CBS data is to have your key read out at the local dealer. How this works is the vehicle’s key will store data from the car about service and mileage. The print-out from the key reader program will show remaining time and mileage for the services. If the service is due, it will put a X next to the service and say “recommend”.
The vehicle decides what is due through different methods. For instance, the brake fluid is time passed only. Every two years the fluid needs to be changed. If you have a new vehicle the first brake fluid service is three years, then it changes to every two years after that. The brakes are calculated out using brake pressure and brake usage. As this mileage counts down, the brake sensors are backup for if the pads wear faster than the calculation. If the sensor is cut, then the service light will turn on. In some of the older models BMW used a two stage brake sensor. When the first loop of the sensor was cut, the CBS data would use this information for adjustment of the brake wear calculation until the last loop is cut.
The oil change is calculated by several items such as oil temp, engine run time, outside air temp, fuel quality. Most new BMWs are on 10,000 mile or one year oil change interval. Some older models are on 15,000 mile, two year oil change interval. This mileage can change on how the car is driven. Let’s say you do weekend track events and push the car through its paces. The mileage for when the oil service is due could change to account for the oil break down.
The included services mentioned are linked to main services. For instance; the oil change can have micro filter, spark plugs, air filter and vehicle check linked. Meaning, when a oil change is due, these other service items could be due as well. The same happens in some older BMWs with brake fluid and micro filter being linked together. Later on, BMW put a micro filter with oil to be changed more often. On M models, some other services are linked with oil change such as: rear diff and possible transmission depending on model and year of the vehicle. Diesel engines will also have a fuel filter service linked to engine oil.
If you look at the picture of a key read above you can see a column called “Service Counter”. This is how many times that service has been done to the vehicle. This feature is how these inclusive items are decided if they are due. For example, spark plugs that are linked to oil service on some models are due every three oil services. This is where the service counter comes into play…for when that service would be due.
I know this seems like German engineers are reinventing the wheel in a confusing way. The main reason deduced is likely to save money on maintenance costs during the warranty period. Once this concept is understood, it can make maintaining your BMW much easier!