MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
Are the BAS, ASR, and ABS lights staying ON in your Mercedes-Benz? This article will show you how to troubleshoot BAS/ASR light problems. What ASR, BAS, and ABS lights mean. Common problems and possible solutions.
Common Mercedes BAS & ASR Problems
- ABS/ ASR/ BAS Fault Codes
- BAS/ASR Light Stay On Instrument Cluster
- Mercedes goes into limp mode, stuck in gear
What do ABS, BAS, and ASR lights mean?
If any of these lights turn on and stay ON once you start to drive the car, it means there is a problem with one of the following systems or related sensors.
- ASR Light Meaning – Anti-Slip Regulation / Acceleration Skid Control
- BAS Light Meaning – Brake Assist System
- ABS Light Meaning – Antilock Brake System
Troubleshooting BAS, ASR, and ABS Lights
Step 1: Ensure that the main battery on your Mercedes-Benz is holding a proper charge. Mercedes-Benz cars are very sensitive to low voltage. An old battery can cause BAS and ASR lights to stay on. It is common for the BAS and ASR lights to come on with a dead battery. It takes a while for a discharged battery to charge fully. Your Mercedes-Benz battery should have its manufacturing date stamped on top or the side. If your battery is over ten years old, consider replacing it even if the car has been starting fine. Don’t wait until your Mercedes battery is completely dead.
If you need a reasonably priced Mercedes battery, read this article: Top 5 Batteries for Mercedes-Benz.
Step 2: Check the brake light switch. The brake light switch is probably one of the main causes that trigger BAS and ASR light problems. The switch doesn’t only turn on the brake lights on the rear, but other systems, including ABS, ASR, and BAS, also use the input from the switch.
To check if the brake light switch is the problem, pay close attention when the BAS and ASR lights come on.
Do ASR and BAS lights come on when you press the brake pedal?
If the ASR and BAS lights come on when you push the brake pedal, the brake light switch is most likely the problem.
It is not worth repairing the original brake light switch. Since the brake light switch is relatively cheap (check prices on Amazon) and often the main problem is that it is better to replace it. Replacing the brake light switch is easy. Watch the following video on changing the brake light switch on a Mercedes-Benz.
Step 4
If you replaced the brake light switch and are still having problems with the BAS/ASR lights, the next thing to check would be the ABS wheel speed sensors. They are installed on two (diagonal) or all four wheel knuckles and measure wheel revolutions.
How do you know that the ABS sensors are defective?
The best way to diagnose an ABS sensor is to use a diagnostic scanner such as the YOUCANIC full system scanner. Note that you need a full system scanner, and a basic OBD-II scanner can only diagnose the check engine light and will not read/erase codes related to ABS, BAS, and ASR. Click here for a comprehensive guide.
Let’s say you don’t have such a scanner or can’t invest in one yet.
Here is a tip: Pay close attention when your BAS and ASR lights come on.
Why do the BAS/ASR lights come on when you start driving but not when you press the brake pedal?
Typically, this happens when one of the ABS sensors is defective. The BAS/ASR light usually comes on when you exceed five mph.
Step 5
Check the rear brake lights. Do they work properly? Does the third brake light work? It is not common for a short to develop in the brake light circuit and cause such problems. Unplug the rear brake lights and check for corrosion if the rear brake lights don’t work. Check the connections that plug into the brake light assembly. You may want to use a digital multimeter to check continuity or to ensure there is no short. In a few cases, we have seen wires inside the headlight & tail light fried and causing shorts and malfunctions.
Conclusion
We hope one of these article’s tips will fix your BAS and ASR light problems. Check the brake light switch, car battery, and ABS wheel sensors. If you still have BAS/ASR light problems, it may be time to have an auto mechanic or a Mercedes-Benz dealer perform a diagnostic. Or, if you are a DIYer, use the YOUCANIC full system scanner to run a diagnostic yourself.
If you want to figure out the BAS/ASR problem on your own, you will need to get hold of an advanced diagnostic scanner to do a complete system scan and read the fault codes. The error codes will give you a good idea of the cause of the BAS and ASR lights staying on. Other possible problems triggering the BAS/ASR light are a defective SAM module, a bad ECU, or ABS module.
A YOUCANIC full-system diagnostic scanner can help you troubleshoot Mercedes-Benz problems by interpreting fault codes, performing diagnostic tests, and resetting maintenance reminders. This tool provides valuable information for informed decision-making on repairs and maintenance, making it a powerful asset for DIY mechanics and professional technicians.
Would anybody trust Firestone to fix wheel sensors. Lastly, will the warning lights go off after they finish.
Sure why not. If the ABS light was turned on due to a bad wheel speed sensor, the light usually goes off after the fix. There will be stored codes though. Ask the mechanic to read codes before the repair and clear them afterward.
Would you trust a firestone to replace wheel sensors and the magnet on each wheel. Lastly, will the warning lights on the dash go off.
New bat in, did the wheel turn thing several times, light still comes on about 30 sec after starting down the road.??
Most likely a wheel speed sensor or the ABS pump itself are defective.
This is great help. My 2000 e320 wagon was rear ended, and this makes sense. I will fix it now.
Thanks a lot!