The first automaker to use warning lights was the Hudson Motor Car Company in the 1930s. It was a rudimentary alert that allowed drivers to see that something was wrong with the vehicle.
The goal of this warning was to create something that anyone could see that would prove there was a problem. That’s why it came to be known as the “idiot light.”
This option was the primary feature for warning lights until automakers introduced computerized engine controls in the 1980s. That’s when the older warnings were replaced with more specific options.
Today’s vehicles have dozens of potential warning lights to review. If you’re driving a Mercedez-Benz, three common ones are the BAS, ESP, and ABS.
BAS ESP ABS Mercedes-Benz
The BAS-ESP-ABS warning lights are a problem that impacts all Mercedes-Benz models. BAS stands for “Brake Assist System.” ESP means “Electronic Stability Program.” ABS is the “Anti-Lock Braking System.” When drivers see one of these warning lights appear, it indicates a problem requires review.
Although most automakers use some version of the BAS, ESP, and ABS systems, they don’t tie them together as Mercedes-Benz does for the warning system.
It’s not unusual for drivers to see several other warning lights turn on when something happens that initiates a problem in one of these categories.
If you’ve encountered a problem with the BAS, ESP, or ABS warning lights, here are some fixes that can help you potentially solve the issue without a significant repair.
1. Reset the Lights
When you’ve recently recharged or replaced your battery in a Mercedes-Benz, it causes the three warning lights to appear on the instrument cluster.
It’s similar to the experience you receive when starting the vehicle. For a moment, all the HUD lights appear to show that they’re working.
After starting your Mercedes-Benz:
- Crank the steering all the way to the right.
- Steer all the way to the left while the vehicle remains safely parked.
- After repeating this action two or three times, reset the wheels to neutral and turn off the engine.
Restarting the vehicle after taking those actions should stop the warning lights from displaying at inappropriate times.
2. Check the Brake Light Switch
The most common repair issue that causes the BAS, ESP, and ABS warning lights to display on Mercedes-Benz vehicles involves the brake light switch.
It’s particularly problematic in the E320, C240, CLK, and SLK models.
This repair is relatively easy to complete. The first step is to find an appropriate switch that works with your vehicle.
The URO Parts Brake Light Switch is compatible with most Mercedes-Benz models. If you input your vehicle into the Amazon Confirmed Fit feature, you’ll know for sure that the product works.
You can find the switch right above the brake pedal. Remove the malfunctioning one, replace it with a new product, and restart the vehicle to see if the problem corrected itself.
3. Replace the Battery
Older batteries installed in Mercedes-Benz models can cause the ESP and BAS warning lights to appear. That’s because the unit no longer supplies the necessary voltage to the vehicle’s control units.
If you connect a diagnostic scanner to the car, you will find under-voltage faults stored. That indicates it is time to replace the battery.
You might see other warning lights appear when the battery fails.
Any battery more than five years old should be replaced. That way, you won’t get stuck somewhere if the product fails.
Replacing a battery in a Mercedes-Benz is a relatively simple procedure. You need to remove the two battery terminals, then the bolted bracket, to lift the battery out of place.
Once the old battery is gone, you can put the new one in by following the removal order in reverse.
Most Mercedes-Benz vehicles use Group 49 batteries. The ACDelco Gold provides a 36-month warranty to ensure you receive protection for this investment.
Its high-density negative paste improves the vehicle’s overall performance, while the ribbed case works to prevent future leaks proactively.
4. Check the ABS Wheel Speed Sensor
If the ABS sensor fails on a Mercedes-Benz, it can trigger the BAS, ESP, and ABS lights on the heads-up display.
Since the ESP system requires the ABS to function correctly, you’ll have both disabled if the speed sensor fails.
You might see other lights appear with this problem, including the Check Engine Light. The car might fail to operate even when it is in drive, or the speedometer can fail.
Each wheel on a Mercedes-Benz comes with an ABS speed sensor. They’re not difficult to replace, but you’re stuck buying four if you’re unsure of the one that failed.
The price you’ll pay for a new sensor depends on the make and model of Mercedes-Benz you currently drive.
5. ABS-ESP Control Module Failure
The ABS-ESP control module reads the speed data from several sensors when driving a Mercedes-Benz. That includes the clock spring and the ABS wheel sensors.
The module applies pressure to the vehicle’s brake pads depending on the directions received from the vehicle control unit.
Although this part is less likely to fail than others that cause the BAS, ESP, and ABS warning lights to appear, it is not a rare problem.
Unless you have familiarity with repairing Mercedes-Benz vehicles, this job is better left to the professionals.
You can open the ABS pumps to see if the brushes have worn out to determine if replacements are necessary.
What If the Check Engine Light Comes On with the BAS-ESP-ABS Combination?
When the Check Engine Light appears on your HUD while driving a Mercedes-Benz with the BAS-ESP-ASB combination, it can mean that a general error occurred.
It can also mean that you’ve got one or more of the conditions listed above in this guide causing a malfunction.
Although seeing the Check Engine Light appear can be scary, the actual issue could be one of several problems.
Here is an overview of the common problems that trigger this condition so that you can proceed with a potential repair.
| CEL Problem | How to Repair the Check Engine Light Issue |
| Fuel Cap Issue | When the fuel cap is missing or loose, it can sometimes trigger a warning light issue while driving a Mercedes-Benz. If you’ve checked and it is tight, that means the seal is faulty and requires replacement. Although the vehicle still operates, you’ll see your fuel economy decrease. |
| Oxygen Sensor Problem | This sensor determines how much oxygen is present in your vehicle’s exhaust. It lets the engine perform at its best by adjusting the amount of fuel needed. When the part malfunctions, your Mercedes-Benz will use more fuel than necessary. |
| Spark Plug Issue | Faulty or old spark plugs can sometimes cause the CEL to appear. Issues with the wires also create this warning. Since these components produce power and help the engine turn, their failure weakens engine performance or causes it to fail to start. |
| Catalytic Converter Problem | This component helps transform the chemicals created during the engine’s combustion process into something less harmful to the environment. When it malfunctions, you might notice performance changes. If you’re lucky, it might just need a quick cleaning to remove a clog. A complete replacement requires a bigger investment. |
| Battery Failure | If the battery is undercharged, faulty, or leaks, the warning lights can appear on the HUD. When there isn’t enough power to send energy to your electronics, you might not see any lights or functionality from the vehicle. |
| MAF Failure | The mass airflow sensor sometimes triggers the Check Engine Light because its job is to detect how much air goes into the engine. That information lets your vehicle know how much fuel is needed for smooth operations. If you change your filters regularly, you can typically avoid this problem. |
| EGR Valve Issue | This part is responsible for lowering the combustion temperature in the engine. It reroutes some of the exhaust gases by routing them back to the intake. If more or less occurs than expected, it’ll activate the warning lights in your Mercedes-Benz. |
| Vacuum Leak | The vacuum system has connections to several parts, including the heating and cooling system, brake booster, and cruise control. When the rubber hose lines experience damage or crack from age, the warning lights appear on the vehicle. |
As you can see, the warning lights a Mercedes-Benz offers can indicate numerous potential issues.
When you see the BAS, ESP, and ABS light up, that information lets you know something needs to be reviewed.
Many of the fixes tend to be easy to correct, but a few could require the help of a professional mechanic.
What Can I Do When Warning Lights Appear on My Mercedes-Benz?
If the check engine light or the BAS-ESP-ABS combination appears while driving and everything seems fine with the vehicle, don’t panic. Don’t ignore the problem either. The vehicle should be seen by a mechanic, or a diagnostic test run completed, to get to the source of the problem.
I had a unique problem with my Mercedes-Benz that caused the warning lights to appear.
The second cylinder in the engine would occasionally misfire, causing the BAS, ESP, and ABS lights to turn on with the check engine light.
Each time I had the diagnostic test run, the codes would indicate the misfire. My mechanic would reset the vehicle, and I’d be on my way for another month or two before it happened again.
That’s why a professional review is important. You can take the steps here for many of the problems that cause the warning lights to appear, but it may be better to speak with your dealership if the vehicle is still under warranty.
