This guide discusses the common problems that turn on BMW Check Engine Light (CEL), also known as Service Engine Soon (SES).
What does BMW Check Engine Light mean?
If your BMW check engine light (or service engine soon light) stays on, it means that the Onboard Diagnostic System (also known as Digital Motor Electronics DME) has detected a problem with the emission system, engine, or transmission.
BMW check engine light may come on due to something as simple as a loose gas cap, but it can also indicate an expensive engine or transmission problem.
It doesn’t mean your BMW needs to be towed unless the car is overheating or if the check engine light is flashing. If your BMW check engine light continues to flash, continuing to drive can lead to more serious and costly problems down the road.
If the check engine light or service engine soon stays on, your BMW may drive fine if the trigger is due to an EVAP-related fault code.
Unless the problem is more serious, in which case you may notice performance issues such as:
- BMW engine misfire
- BMW won’t accelerate
- Stuck in limp mode
- Engine shakes at idle.
- BMW engine overheats
- Poor acceleration
- Erratic idle
- Hard to start
BMW Service Engine Soon light may be on without any noticeable performance issues.
What does the BMW check engine or service engine soon light mean?
Your BMW’s check-engine light warns the driver that something isn’t quite right with its functionality – the problem can be very simple or severe. If severe, check engine light will flash, leading to the transmission getting stuck in limp mode to prevent further engine damage.
These issues can range in severity, from a loose gas cap to a serious engine malfunction like timing chain failure.
Hundreds of problems may trigger the check engine or service engine soon in a BMW. BMW-specific problems include:
- Cracked or loose hoses
- Old battery
- Bad mass air flow sensor,
- Low fuel level,
- Bad charcoal carbon canister,
- Wire harness,
- High-Pressure Fuel Pump (HPFP) failure,
- Crankshaft sensor bad
- Injectors (when applicable).
Do not start replacing BMW parts without reading the fault codes.
If you don’t have a BMW scan tool, have a shop specializing in BMWs read the codes and troubleshoot the problem. Your local auto parts store may read your BMW check engine light free.
Once you have a diagnosis, you can decide if the repair is something you can tackle yourself or let a BMW shop complete the work.
What to do when the BMW check engine light turns on?
The first step is to check the fuel cap. If the cap is loose, it will trigger the CEL. Tighten it until you hear it click.
Most 2005 and newer BMWs will also show a separate symbol to remind you if you forget to tighten the fuel cap. If the gas cap was loose and you tightened it. The CEL light will reset itself in a few driving cycles, typically within a day or two.
If the BMW drives fine, closely monitor the engine temperature. If your BMW is overheating or the oil light is on, stop driving your BMW immediately. Get the BMW towed if necessary.
You need to read fault codes to find out why your BMW check engine light is on. This is a simple procedure you can perform yourself.
How to diagnose BMW check engine light
These instructions show you how to read and clear codes for checking a BMW’s engine lights. Diagnosing BMW’s check engine light with an OBD-II scanner that can read BMW-specific fault codes such as YOUCANIC Full System Scanner is preferred.
- Locate the diagnostic port on your BMW. The port is under the dash on the driver’s side.
- Plug the scanner into the OBD2 port. Turn on the ignition by pressing the start button without pressing on the brake pedal.
- Allow the scanner to turn on.
- Press read/enter to read codes from DME Module.
- Please write down the codes and clear them once you are completed.
This procedure only allows you to read and clear codes from the ECU / DME / DDE.
A generic OBD2 scanner will not read and clear the codes if you have other problems. In other words, a generic OBD2 scanner can only read and clear codes from the ECU but not from other modules, including ABS, SRS, Airbag, DSC, Stability Control, EGS Transmission, etc.
Note that you can read the codes but can’t clear them unless you fix the problem that triggered the code. The light and the code will return if you don’t fix the underlying problem. It returns immediately or in other cases, it can take a day or two.
BMW Check Engine Light Symbol
There is a difference between BMW Check Engine Light vs. Service Engine Soon.
BMW Check Engine Light Flashing On and Off
If the check engine light is flashing, it generally means that the DME module has detected a misfire. You will notice poor acceleration and BMW engine shaking if the light is flashing.
This problem is often caused by bad spark plugs or a bad ignition coil, a common problem with many BMWs, including 1, 3, 5, 6, X1, X3, and X5 series.
Other possibilities include a vacuum leak, a bad mass airflow sensor, a clogged catalytic converter, and a blown head gasket. It is not recommended to drive a BMW if the service engine light is flashing.
When BMW’s service engine soon light is flashing, and the car is shaking, you have a problem that needs to be addressed as soon as possible. Under these conditions, your BMW will be very sluggish, and the motor will shake at idle.
We hope you find the Troubleshooting BMW Check Engine Light | Service Engine Soon guide helpful. Check these troubleshooting and repair guides for more help on your BMW.