So you are driving down the road and suddenly get greeted with several warning lights and malfunctioning errors. such as:
- Run-flat indicator inoperative
- ABS and ESP inoperative See Owner's. Manual
- ABS and ESP are currently unavailable see owner manual
- ESP inoperative see owners manual (yellow or white)
- Parking brake see owners manual ( in red, less common warning )
The most common problem that causes Run-flat indicator inoperative, ABS, and ESP Inoperative warning lights to come on simultaneously is a bad ABS wheel speed sensor. ABS wheel speed sensors can fail due to the age of the vehicle. If you recently hit a pothole, then there is a high chance one of the ABS wheel speed sensors got damaged.
The second most common issue that triggers run-flat, ABS, ESP warning lights on a Mercedes-Benz is a weak or dead 12-volt car battery. In some cases, power steering may also get disabled, and the steering can feel very stiff.
If you get this warning, pull over, turn off the ignition, remove the key and wait a couple of minutes. Restart the engine, and the notification may clear. If it doesn't, keep on reading.
Depending on the cause, run-flat inoperative, ABS, ESP, and EBD warning messages may be intermittent or stay on all the time. In addition, cruise control and Speedtronic Inoperative warnings may come on if the vehicle is equipped with those systems.
These errors may also come up if the vehicle has electrical issues, which should be addressed before trying to resolve the run-flat, ABS, and ESP malfunction. We have also seen this warning come up in rare cases because of a parasitic current draw when the vehicle is parked overnight or for a few days. A parasitic draw can be caused by an unrelated issue such as a bad alarm siren, horn, sound system, command, or module that doesn't sleep and drains the battery. When the vehicle is jump-started, these error messages appear because a low voltage was detected.
Your Mercedes-Benz has one ABS wheel speed sensor at each wheel. We have seen owners start replacing all of them, hoping that will fix the problem.
Run-flat inoperative, ABS, and ESP lights can also be triggered for many other issues such as bad steering angle sensor, low voltage, corrosion, etc. before you do anything, you need to diagnose the vehicle to find out what codes are present.
Here is how to diagnose this problem using most scanners, including STAR diagnostic:
- Connect a diagnostic scanner to the OBD-II port under the dashboard.
- Turn on the ignition. The scanner will turn on.
- Go to Control Unit.
- Select ABS or ESP control module.
- Scroll down to Read Fault Codes and press enter.
On the next screen, you will see a couple of fault codes. On the code description, you will get a message such as "front right ABS wheel speed sensor implausible." Now you know which ABS sensor is faulty and needs to be replaced. Follow this guide on how to replace a Mercedes-Benz ABS Wheel Speed Sensor.
This tutorial teaches you how to read Mercedes-Benz fault codes and scanners that you can use.
Reading the fault codes is very important. While run-flat inoperative, ABS, and ESP are most likely caused by a bad ABS wheel speed sensor, those error messages can be triggered by several other issues.
Here is a list of all possible causes that can trigger warnings such as run-flat inoperative, ABS, and ESP inoperative see operator's manual:
- Defective ABS wheel speed sensor (most common)
- Low voltage. Dead or week 12-volt battery
- Loose ground terminal
- Faulty ABS/ESP module
- Bad fault SAM module
- Water damage
- Loose battery negative or positive terminal
- reluctor (tone) ring is cracked
- Steering angle sensor faulty or needs calibration
- Low tire pressure
- Different size tires/rims
- Extremely cold temperatures
- Damages ABS wheel speed sensor wire or connector
- The vehicle needs a wheel alignment
- Electric parking brake grabbing. Reset parking brakes if they have an ELPB and Adaptive Brakes.
- The brake light switch will trigger ABS and ESP warnings but usually not run flat indicator inoperative.
Reading the fault codes should be the first step in diagnosing run-flat, ABS, and ESP warning messages. In some cases, run-flat inoperative may also disable Power steering malfunction, ABS, Speedometer inoperative, ESP, EBD, and Cruise Control, plus the vehicle may lose power and go into limp mode.
You may be wondering how ABS, ESP, and run-flat inoperative have in common. There are two types of tire pressure monitoring active and passive. The dynamic type has pressure sensors on each wheel and can display the pressure. The passive tire pressure monitoring measures wheel rotational speed. TPMS system needs to determine the wheel revolutions to determine a flat tire. If the vehicle can't get a speed reading from one of the ABS wheel speed sensors, it will trigger run-flat inoperative.