The EML light is something virtually all drivers have heard of because it stands for Engine Management Light in English. That’s just another name for the check engine light. But when it comes to BMWs, EML stands for Elektronische Motorleistungsregelung. A mouthful, I know, but the meaning is pretty straightforward.
EML stands for electronic power control and refers to the electronic throttle body system. The causes of EML light include a bad electronic throttle body, throttle position sensor, gas pedal, vacuum leaks, and ABS system faults.
Eml Light Meaning and How It Works
The EML warning light is not the engine management light or check engine light we are all used to. The EML light in a BMW is spelled out instead of being an engine symbol and stands for Elektronische Motorleistungsregelung. The direct translation would be electric engine power regulation which is misleading. But the real translation is electronic throttle control.
When the EML light comes up, it doesn’t necessarily mean the electronic throttle body is bad. The whole system relies on the electronic gas pedal, throttle position sensor, speed sensors, and the engine control unit. The way it works is the driver opens up the throttle, and a signal goes to the engine control unit.
After that, the engine control unit sends a signal to the electronic throttle body to open to the same degree as the driver’s throttle input. The throttle position sensor then sends a signal back to the engine control unit to confirm that the throttle body has done what it was supposed to do. And the speed sensors don’t directly control or affect the throttle system.
But they can raise some red flags for the engine control unit which monitors both. Diagnosing the EML light is pretty simple as long as you have an OBD2 scanner. Each of the components we just mentioned has its own fault codes, and even vacuum leaks have fault codes. But vacuum leaks also have severe symptoms that are hard to miss.
EML Light Causes and Fixes
1. Faulty Throttle Position Sensor
The throttle position sensor isn’t the most important part of the electronic throttle system. In theory, the system could work without it, but it would be extremely unsafe. And that’s why the EML light comes on if it’s faulty, and the car may even go into limp mode.
The throttle position sensor works by sending a specific voltage signal to the ECU. For example, when the throttle is 10% open, the signal is 0.6 volts, and when it’s 90% open, the signal is 2.4 volts. But once the TPS starts malfunctioning, the signal it sends to the ECU could be out of the normal range it expects, or it could just be wrong.
As soon as the ECU notices that, it triggers the EML light and a corresponding fault code. If the voltage is out of range, it will clearly indicate the TPS is bad. But if it’s still within range, you could get fault codes indicating problems with the throttle body. That’s why testing the TPS with a multimeter is the best way to diagnose this problem.
A new throttle position sensor for a BMW will set you back around $100 at AutoZone, or around $150 to $200 for an OEM part. When it comes to labor, replacing the sensor is pretty easy and only takes about 15 to 20 minutes which comes to around $50. But you can easily replace the throttle position sensor yourself. But if you have a BMW built after 2000, the throttle position sensor will be integrated into the throttle body. In that case, you have to replace the entire unit.
2. Faulty Electronic Throttle Body
The electronic throttle body is the most important piece of the EML light equation. The electronic throttle body has an electric motor or an actuator that opens the butterfly valve that would usually be operated by a cable. Along with the throttle body, there is also a potentiometer that serves as a throttle position sensor in integrated systems.
Some other symptoms you might notice if the throttle body goes are frequent stalling, engine refusing to start, rough idle, poor performance, and fuel economy. You can test the throttle body by having someone turn the ignition on and step on the gas pedal. At the same time, you should remove the intake boot and watch if the butterfly valve reacts to gas pedal inputs properly.
But a simple fault code scan should reveal immediately if the throttle body is bad. A new throttle body will set you back around $200 to $300 at AutoZone or $400 to $500 if you go with an OEM unit. Replacing the throttle body doesn’t take too long at about half an hour which is another $50 for labor. You can also replace the throttle body yourself with some basic tools.
In this video, you can see how to replace a throttle body on the M54 engine.
3. Faulty Gas Pedal
The gas pedal is essentially just a potentiometer that sends a small 0.5 to 2.5-volt signal to the ECU which then controls the electric motor in the throttle body. And potentiometers, especially those from the 2000s are prone to wearing out and failing. When that happens inside the BMW gas pedal, the car will hesitate to accelerate and it won’t go past a specific engine speed.
Other symptoms like rough idle, poor performance, and poor fuel economy are also possible. But the gas pedal has very specific fault codes that make it pretty easy to diagnose. A new gas pedal will set you back anywhere between $150 and $400 at AutoZone depending on model year. Replacing is fairly simple and takes about 0.5 to one hour to replace.
This is also a job you can do yourself with a good guide and save yourself about 100 bucks. The entire gas pedal assembly simply clips into place and there isn’t a single bolt holding it down. If you do it yourself, it won’t take more than half an hour.
You can see how to replace the gas pedal in an E46 BMW in this video.
4. ABS System Issues
The ABS system is what monitors the speed of the vehicle, as well as acceleration. There is a speed sensor on each of the four wheels which helps the traction control system as well, and the traction control system works by closing the throttle body. You can already see the correlation. If one of the speed sensors malfunctions and tells the ECU that the car is accelerating, it might think the throttle body is faulty.
Then, to be safe, it will throw the EML light and possibly trigger limp mode. There is also a chance that the traction control system is trying to close the throttle because of wheel spin, but the throttle body isn’t responding properly. That will also trigger the EML light. The main cause of this is a bad wheel speed sensor.
Along with the EML light, you will also get an ABS warning light and a traction control warning light. The fault codes for the wheel speed sensor are also very specific so diagnosing it won’t be an issue. Replacing it isn’t a problem either and only takes about half an hour to 45 minutes which is about $70 for labor and another $100 for a new sensor. You can also replace it yourself with a couple of jack stands and some basic tools.
5. Vacuum Leaks
Vacuum leaks are one of the most annoying things that can happen to a car. A vacuum leak is when air is going into the engine but after the mass airflow sensor. That could be because of a cracked intake boot, leaking intake manifold gasket, cracked vacuum hoses, and in the case of a BMW, a leaking oil filler cap.
The main symptom of a vacuum leak is an erratic idle speed where the RPMs jump up and down without any driver input. Then, the RPMs surge each time you change gears, performance is bad, it’s difficult to start the engine, and the fuel economy is bad. The fault codes you will get with a vacuum leak are P0171 and P0174. That means the post-cat O2 sensors have detected a lean mixture.
How much it costs to fix a vacuum leak depends on what’s causing it. It could be from a couple of bucks for a new vacuum hose, to hundreds of dollars to replace the intake manifold gasket, but that’s rarely the case. The main problem here is finding the vacuum leak. You can have a professional do that for $50 to $100, or you can make your own smoke machine for $20 and do it yourself.
How to Reset the EML Light
On the off chance that the EML light is triggered by an ECU glitch, a random voltage surge, replacing the battery, or any other random cause, resetting the EML light might just be the only solution you need. So, let’s try that.
Step by Step:
- Press the gas pedal all the way down and hold it there.
- Turn the ignition on but don’t crank the engine. Still holding the gas pedal.
- After ten seconds, turn the ignition off. Still holding the gas pedal.
- After another ten seconds, release the gas pedal and start the engine. If all the throttle body needed was calibration, the EML light should be off at this point.
You can also have a look at this video to see how to reset the EML. You will also see some fixes for the EML light, diagnostics procedures, and guides on how to replace some components.
Can I Drive With the Eml Light On?
As long as your BMW is running fine, it’s okay to drive with the EML light on. But if you notice symptoms like a rough idle, poor performance, jerking, and stalling, it’s better to avoid driving the car to prevent further damage. Driving a car with such symptoms can also be dangerous and fixing the problem may not even be that expensive depending on what’s causing it.
How Do I Fix My Eml Light?
The first step in fixing the EML light is figuring out what’s causing it in the first place. That can be anything from vacuum leaks to a bad electronic throttle body or a gas pedal. Resetting the throttle body can help and it’s a simple procedure we already covered. But if you drive anything other than a BMW, scanning the fault codes first is a must.
Do All Bmws Have an Electronic Throttle?
Not all BMWs have an electronic throttle. Even though BMW was the first manufacturer to install an electronic throttle body in 1988 with the V12 7-Series, it wasn’t until the BMW E46 and the M54 engine that all other models got the electronic throttle body. Before that, only the V12 engines had them.
How Long Do Electronic Throttle Bodies Last?
Electronic throttle bodies should last at least 100,000 miles. But it’s not uncommon for them to fail earlier, and for a lot of models that is a common problem, like the BMW V10, and smaller GM engines from the late 2000s. But in some cars, the throttle body can also last well over 150,000 miles so it all depends on the model.
Is It Better to Clean or Replace the Electronic Throttle Body?
If you are having issues with the electronic throttle body, you can try cleaning it. If there is carbon and sludge around the resting position of the butterfly valve, it can cause an EML light and fault codes. But if the throttle body is faulty, your only solution is to replace it. The throttle body cannot be fixed or cleaned if that is the case.
Can a Bad Throttle Position Sensor Affect Transmission?
The throttle position sensor can affect the way the transmission shifts, and when it shifts. The transmission control unit monitors your throttle inputs. If you push the gas pedal to the floor, the transmission will shift later and faster. And if the TPS malfunctions, it may seem that the transmission is stuck in gear, or that it shifts too hard and is slamming into gears.
Final Words
Given that BMW is the first manufacturer to install an electronic throttle body on a production car, it doesn’t surprise that the system gets its own warning light. However, the warning light isn’t too specific and can be triggered by any of the system components.
That includes a bad gas pedal, a throttle body, and the throttle position sensor. And even a bad wheel speed sensor and vacuum leaks can trigger it. That’s why scanning the fault codes is crucial when trying to fix the EML light.
