BMW’s S65 and S85 are stunning displays of automotive innovation. But these engines are prone to throttle body actuator failures.
If your BMW is going into limp mode and you’re receiving a fault code, the throttle body actuator is a likely culprit. Read on to learn what BMW models are affected, the symptoms of fault codes of throttle body actuator failure, and how to choose between repairing or replacing.
Which Models Are Affected?
Even if you know how to maintain your BMW’s performance, failing throttle body actuators are a common problem for BMW M3, M5, and M6 vehicles fitted with the S65 and S85 engines.
Affected BMW models include:
- BMW M3 2004-2010
- BMW M5 2007-2013
- BMW M6 2005-2011
Throttle Body Actuator Failure Symptoms
We’ve seen throttle body actuators fail at various mileages in S65 and S85 models, typically without warning. If your BMW experiences throttle body actuator failure, your car will likely experience the symptoms below. In many cases, your engine may run fine for a few miles before these symptoms occur.
- Loss of power
- DSC and EML light
Throttle Body Actuator Failure: Common Fault Codes
Common fault codes indicating actuator failure include:
- 2B15 – Throttle Valve Actuator Governor Monitoring/Control Bank 1
- 2B16 – Throttle Valve Actuator Governor Monitoring/Control Bank 2
- 2B21 – Throttle Valve Actuator Pre-drive Check Bank 1
- 2B22 – Throttle Valve Actuator Pre-drive Check Bank 2
- 2B25 – Throttle Valve Monitoring Bank 1
- 2B26 – Throttle Valve Monitoring Bank 2
Why S65 V8 and S85 V10 Engines Experience Throttle Body Actuator Failures
S65 V8 and S85 V10 engines feature an individual throttle body for each cylinder but these throttles are not driven individually. There is a single actuator for each side of the engine that is attached to either four or five throttles allowing electronic control of the two actuators to handle all eight or ten cylinders.
This setup ensures that each cylinder on the same bank will have the same throttle valve angle and the same amount of airflow, which simplifies the electronic motor control’s job. There is nothing fundamentally flawed with this design except for the plastic gears used in the actuator motors, which wear over time and cause the circuit boards to burn out.
S65 and S85 Throttle Actuator Replacement
There are several ways you can go about replacing your BMW’s throttle actuators, but typically you’ll have to choose between rebuilding or replacing.
Rebuild kits are available which replace the plastic gears with stronger, more durable ones. These are useful for cars that have not yet started exhibiting any symptoms or fault codes.
As the plastic gears wear, moving the throttles becomes more difficult, which leads to failure of the electronic circuit board. Replacing the gears early prevents this situation, but it’s still possible for the actuator to eventually fail if it’s already been dealing with worn gears.
We no longer recommend rebuilding since the cost of labor is still high, and these engines have been around for too long to make this a worthwhile preventative upgrade at this point.
Once an actuator has failed and the vehicle exhibits the fault codes above, the engine will go into limp mode with significantly reduced power output. At this point, the dead actuator will need to be replaced and it makes the most sense to do both at once to avoid paying labor again to remove and replace the second actuator when it eventually fails.
Whether you choose to rebuild or replace one or both of your actuators, the labor involved is nearly the same: about five hours.
Replacing both actuators with the latest part numbers means you shouldn’t need to worry about another failure. The current actuators are upgraded over the original parts installed in the M3, M5, and M6 and the weaknesses have been addressed.
For this reason, we feel that actuator replacement is the permanent solution to the problem.
HG Performance Knows BMW
At HG Performance, our qualified team of technicians has the experience and expertise needed to repair your BMW. Our technicians take the guesswork out of BMW repairs and offer customized service through our extensive knowledge of each BMW model.
Contact us online or at 858.943.0891 if you have any questions about your bimmer or to request an appointment.