In this guide, we will go over the most common causes that trigger BMW Check Engine Light (CEL) and how you can diagnose and reset this light yourself.
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If the check engine light or service engine soon stay on, your BMW may drive fine if the trigger is due to 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.
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Common Causes of Check Engine Light
There are hundreds of problems that 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 at a reading the fault codes. If you don't have a BMW scan tool, have a shop that specializes in BMWs read the codes and troubleshoot the problem for you. Once you have a diagnosis performed, you can decide if the repair is something that you can tackle yourself or let a BMW shop complete the work.
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What does BMW Check Engine Light mean?
If your BMW check engine or service engine soon light turns on it means that there is a malfunction with the emission system or the engine itself. When BMW service engine soon light stays on, it means the Digital Motor Electronics DME (BMW term for Engine Control Unit - ECU) has detected a problem you will need to read the fault codes.
Service Engine Soon (SES) and Check Engine Soon Light (CEL) on a BMW will come on if the Digital Motor Electronics DME detects a problem with engine's operation or emission system. When engine warning light stays ON constantly, it means there is a Diagnostic Trouble Code (DTC) present in the system.
Don't panic! It doesn't mean your BMW needs to be towed unless the car is overheating or if the check engine light is flashing. The good news is that you can read the codes yourself without spending a fortune. Often the issue is not as serious as you may think.
Follow the steps below to diagnose BMW CEL yourself. It is important to read the codes as soon as possible. Ignoring a flashing CEL or SES light can lead to more serious and costly problems down the road.
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What to do when BMW check engine light turns on?
The first step is to check the fuel cap. Tighten it until you hear it click. If the cap is loose it will trigger the CEL. If you believe the gas cap is the problem, retighten or replace the gas cap and drive the car as normal. Within two to three days the check engine light will turn itself off. No need to clear codes or use a scanner for a loose gas cap. If the light stays on, you need to read the codes.
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 tighten 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 and make sure the oil light isn't staying on. If your BMW is overheating or oil light is on, stop driving your BMW immediately. Get the BMW towed if necessary.
Next, you need to read fault codes.
This is a simple procedure you can perform yourself. One option is to use a cheap generic OBD2 code reader but keep in mind that a generic OBD2 code reader will not provide details as would an OBD2 scanner that is designed to read BMW specific fault codes. A generic code reader will provide generic fault codes that don't translate properly for BMW. Several auto parts stores such as Advance Auto Parts and Autozone may read the codes free of charge. Once you retrieve the code, do online research to find what that code means on BMW.
If the codes retrieved from the generic OBD2 scanner don't provide enough information you will need to read the fault codes with a BMW scan tool. One option is to take your BMW to an auto repair shop that specializes in BMW or buy a BMW scan tool and perform the procedure yourself.
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How to reset BMW check engine light
These instructions show you how to read and clear codes related to check engine light on a BMW. In this guide, we use two of the most popular BMW scan tools. Of course, these are not the only scanners that can diagnose BMW check engine light. To learn more about various scanners read this article on Choosing the Best OBD2 Scanner for BMW.
Read BMW check engine codes using Foxwell NT510 for BMW
What we used: Foxwell NT510 for BMW
Read DTC fault codes using BMW Carly for BMW
In this guide, we use a Level 2 OBD2 Scanner that can read BMW specific fault codes from the DME module. A BMW scan tool will provide a better description of the fault code and even display fault codes that may not be picked up by a generic OBD2 scanner.
What we used:
- Carly for BMW adapter
- Carly for BMW App
Read fault codes using a generic scanner
In this section, you will learn how to use a generic OBD2 scanner some of which cost as little as $15 to read BMW fault codes.
What you need:
- Generic OBD2 scanner.
- Even a $15 OBD2 scanner or an ELM327 Bluetooth adapter that pairs with your phone is able to read codes related to the check engine light. Once you retrieve the code, perform an online search to find out what it means for BMW.
- Determine the status of check engine light on the instrument cluster.
- Locate OBD2 port on your BMW. The port is under the dash on driver's side.
- Plug scanner into the OBD2 port. Turn on ignition by pressing the start button without pressing on the brake pedal.
- Allow the scanner to turn on. Press read/enter to read codes. 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. If you have other problems a generic OBD2 scanner will not be able to read and clear the codes. In other words, generic OBD2 scanner are only able to read and clear codes from the ECU but not form other modules including ABS, SRS, Airbag, DSC, Stability Control, EGS Transmission etc.
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Note that you can read the codes, but you can't permanently clear them unless you fix the problem that triggered the code. If you don't fix the underlying problem the codes light will return. In some cases, it returns right away, in other cases it can take a day or two.
Various BMW CEL Symbols
There is a difference between BMW Check Engine Light vs. Service Engine Soon
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- Check Engine Light - Yellow CEL
- Engine Block Symbol in Dashboard
- Problem is often minor such as loose gas cap
- Often BMW drives fine
- Service Engine Soon - SES Light
- SES light doesn't always mean there is a major engine problem.
- BMW may run and drive fine.
- Don't ignore this light. Read BMW fault codes.
- Check Engine Light - Half Yellow
- Means problem is more severe.
- Car usually goes into limp mode to prevent further damage.
- Serious engine or transmission problem
- BMW may be stuck in gear, Limp Home Mode
Check Engine Light Flashing
If the check engine light is flashing, generally means that the DME module has detected a misfire. If the light is flashing you will notice poor acceleration, BMW engine shaking. This problem is often caused by bad spark plugs or bad ignition coil which is a common problem with many BMWs including 1, 3, 5, 6, X1, X3, X5 series. Other possibilities include vacuum leak, bad mass air flow sensor, clogged catalytic converter and blown a head gasket. It is not recommended to drive a BMW if the service engine light is flashing. When BMW service engine soon light is flashing and 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. The problem is often caused by a bad ignition coil or spark plug. Read the codes as soon as possible and fix the underlying problem.
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Do not continue to drive a BMW with flashing check engine light for an extended distance. Driving a BMW with check engine light flashing, engine shaking can cause expensive damage to other components including the catalytic converter.
Cost to diagnose BMW check engine light
The typical cost to diagnose BMW check engine light can vary from $60-$130. BMW dealerships generally charge one-hour diagnostic. Shops that specialize in BMW may charge only 30 minutes of labor. A few BMW shops may even scan your BMW CEL codes free of charge. During this procedure, an auto technician will plug a diagnostic scanner into the OBD2 port and read the codes from the DME DDE module. You can perform the same procedure yourself by using an OBD2 scanner that can read BMW specific fault codes.
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