BMW Start Stop Not Working: Solutions for a Reliable System

Understanding the BMW Start/Stop Technology

The BMW Start/Stop technology, also known as auto start/stop, is a fuel-saving feature implemented in various BMW models. This system automatically shuts off the engine when the vehicle comes to a complete stop, such as at traffic lights or while idling in heavy traffic. When the driver resumes driving by releasing the brake or engaging the clutch, depending on the transmission, the engine quickly restarts. This feature aims to reduce fuel consumption and carbon dioxide emissions, contributing to a more environmentally friendly driving experience.

The Start/Stop function of a BMW operates utilizing sensors that monitor various factors such as vehicle speed, engine temperature, battery charge, climate control settings, and transmission status. Depending on the combination of these factors, the auto start/stop system calculates the optimal timing for engine shutdown and restarts.

There might be instances where the BMW auto start/stop system may not function as expected due to several reasons. One common issue is the battery not being adequately charged, as the technology relies on the battery’s charge to function efficiently. Ensuring that the battery is maintained and charged sufficiently can help mitigate this problem.

Another factor that may affect the Start/Stop system is the presence of dirt or damage on the related sensors. Cleaning the sensors with a soft cloth can potentially resolve this issue. In addition, extreme weather conditions or heavy use of auxiliary functions, such as air conditioning, can temporarily disable the auto start/stop function to ensure overall vehicle performance.

The BMW Start/Stop technology is a convenient and eco-friendly feature that helps drivers save fuel and reduce emissions. However, understanding its functionality and potential issues can help BMW owners troubleshoot and maintain the optimally functioning auto start/stop feature in their vehicles.

Problems with BMW Start/Stop Not Working

Engine Condition

The BMW start/stop system relies on the engine being in good working condition for proper functioning. A worn or damaged engine component might cause the system to malfunction, disrupting the start/stop feature. Keeping up with regular engine maintenance can help prevent issues with the start/stop system.

Battery State of Charge

The start/stop system depends on the battery having a sufficient charge to ensure smooth running. Frequent short trips or using many electrical features at once can lead to a low battery state of charge, preventing the start/stop feature from working efficiently. Ensure that the battery is frequently charged and in good condition to maintain the start/stop function.

Brake Pedal Position

For the start/stop system to work properly, the brake pedal must be pressed firmly before the engine shuts off. If the brake pedal is not fully engaged or if there are issues with the brake servo, the start/stop function might not operate correctly. Regular brake system maintenance and checking the brake pedal position can help avoid problems.

Transmission State

The start/stop system is designed to work only when the transmission is in a specific state, such as being in neutral or with the clutch engaged. If the transmission is not functioning properly, it can prevent the start/stop system from working. It is essential to address any transmission issues to ensure the smooth operation of the start/stop feature.

Operating Temperature

Like many other vehicle systems, BMW start/stop requires the engine to be at an optimal operating temperature. The system might not work efficiently at low temperatures or when the engine is cold. Ensuring that the vehicle reaches its ideal operating temperature before using the start/stop feature can help prevent potential issues.

Starter and Alternator Health

The starter motor and alternator are essential components of the start/stop system, being responsible for restarting the engine after it has been temporarily stopped. A failing starter motor or a malfunctioning alternator can disrupt the start/stop functionality. Regularly inspecting and maintaining these components can help keep the start/stop system running efficiently.

Effects of Various Vehicle Conditions on Start/Stop Functionality

Role of Air Conditioning System

The air conditioning system plays a significant role in the operation of the start/stop functionality in BMW vehicles. When the air conditioning is in use, it may prevent the auto start/stop feature from engaging. This is primarily due to the additional power requirements of the air conditioning system. However, modern BMW vehicles are designed to take the load of the air conditioning system into account, allowing the start/stop functionality to work more seamlessly without causing discomfort for the occupants.

Effect of Outside and Engine Temperature

Both outside and engine temperature can also have an impact on the start/stop feature. If the engine temperature is too low, the start/stop functionality will not engage to prevent potential damage to the engine components. Conversely, if the engine temperature is too high, the system will also not activate the auto stop/start to prevent overheating. In addition, extreme outside temperatures can also affect how efficiently the system functions. For instance, on extremely hot or frigid days, the start/stop functionality might work less frequently to maintain a comfortable cabin temperature.

Impact of Vehicle Speed and Drive Mode

Vehicle speed and the selected drive mode are other factors that can influence the start/stop functionality. Typically, the auto start/stop function is designed to operate more efficiently in urban environments, where cars frequently stop and go at lower speeds. During highway driving, where speeds are generally higher, the start/stop function may not engage as often, as the benefits of fuel saving become less noticeable.

In addition, the BMW vehicles offer different driving modes, such as Eco Pro, Comfort, and Sport mode. These modes can impact the start/stop functionality based on the priority given to fuel efficiency or performance. For example, in Eco Pro mode, the start/stop function may be more aggressive to prioritize fuel savings, while in Sport mode, the system might prioritize performance over fuel efficiency and keep the engine running for faster response times.

Diagnosing the Problems with BMW Start/Stop

Role of Vehicle Internal Network

The vehicle internal network plays a crucial role in the functioning of the BMW Start/Stop system. It consists of multiple microprocessors, control modules, and sensors that communicate with each other to operate the system efficiently. Any issues within this network may cause the Start/Stop feature to malfunction. In order to diagnose the problem, it’s essential to inspect the connection between different components and verify if they are functioning correctly.

Using Diagnostic Trouble Codes

Diagnostic Trouble Codes (DTCs) help in identifying the source of issues within the BMW Start/Stop system. Modern BMW vehicles are equipped with an On-Board Diagnostic (OBD) system that stores DTCs when a problem is detected. To access the stored codes, you’d need an OBD scanner. By connecting it to your vehicle’s OBD port, you can retrieve the stored codes and get insights into the possible issues. These codes help technicians and vehicle owners in pinpointing the root cause and guide them in effectively resolving the problem.

Checking the Control Units and Sensors

Various control units and sensors have been employed in the BMW Start/Stop system to ensure its smooth operation. Some of them include:

  • Control Module: The control module sends signals to the different components ensuring the proper functioning of the Start/Stop system. If there’s a problem with the control module, it may result in the malfunctioning of the entire system. Inspecting the control module or having it scanned with an OBD scanner can help identify any likely issues.
  • Sensors: Sensors play a vital part in determining when to activate or deactivate the Start/Stop feature. For instance, the system relies on sensors that monitor engine temperature, battery voltage, and vehicle speed. Malfunctioning of any of these sensors could cause the feature not to work as intended. Checking these sensors and their connection to the vehicle internal network could help determine and resolve the problem.

In conclusion, diagnosing problems with BMW Start/Stop systems involves assessing the vehicle’s internal network, utilizing diagnostic trouble codes, and inspecting control units and sensors. A comprehensive diagnosis can help identify the root cause, fix the issue, and keep the system working efficiently.

Solutions for BMW Start/Stop Issues

Battery and Alternator Check

One of the common reasons for the start/stop feature not working in a BMW is an issue with the battery or alternator. To ensure that the system functions properly, the battery must be sufficiently charged and the alternator should be in good working condition. If the battery is weak or the alternator is not charging the battery effectively, the start/stop system may not work as intended. It is essential to check the battery and alternator regularly, and if necessary, replace or repair any damaged or worn-out components.

Software Updates

Another possible solution for BMW start/stop issues is updating the vehicle’s software. With advancements in vehicle technology, manufacturers often release software updates to fix bugs or optimize performance. Outdated software can sometimes cause the start/stop system to malfunction. To resolve this issue, take your BMW to an authorized service center or dealer to have them check for software updates related to the start/stop system and install them if needed.

Deactivating the Start/Stop System Temporarily

In certain situations, BMW owners might prefer to temporarily deactivate the start/stop function. To do this, press the start/stop button, usually located near the gear selector or on the center console. Keep in mind that deactivating the system is only a temporary solution, and it will not address the root cause of the problem if your BMW’s start/stop system is malfunctioning. It is still essential to diagnose and repair any issues to ensure the vehicle’s optimal performance and fuel efficiency.

Georg Meier

BMW technician since 1996. I began my automotive journey in 1993 as an apprentice mechanic at Automag, the world's oldest BMW dealership in Munich. With years of experience and dedication, I garnered a wealth of knowledge about the intricacies of BMW and MINI vehicles. The love/hate relationship with the brand led me to found BIMMERIST where I share expertise and insights with fellow enthusiasts.

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