By Core Brake Parts Tech Team — Circleville, OH warehouse
A yellow ABS light on a 2020-2024 Mercedes-Benz GLE350 means the control unit has found a fault in the anti-lock system and has switched ABS off. Your normal brakes still work, but the wheels can lock in a hard stop and ESP stability control is usually off too. The most common causes are a failed or dirty wheel speed sensor, damaged sensor wiring, a problem at the wheel bearing encoder, or low system voltage - and on 2020-2021 trucks, check whether an open ESP software recall applies.
How ABS and ESP Work on the GLE350
The current GLE, including the GLE350, uses one braking control system for ABS, EBD (electronic brakeforce distribution), BAS brake assist and ESP stability control. Mercedes describes ABS as regulating brake pressure in critical situations so the wheels do not lock and the vehicle stays steerable; when it works you feel a pulsing in the pedal.
Every one of those systems depends on four wheel speed sensors. Bosch uses Hall-effect wheel speed sensors that read a magnetic or steel encoder turning with the wheel and send a digital pulse signal whose frequency matches wheel speed. Bosch states these sensors can detect speeds as low as 0.1 km/h, and the same signal feeds both ABS and ESP. That is why one bad sensor almost always takes out ABS and ESP together on this SUV.
The GLE350 has disc brakes on all four wheels and an electric parking brake, and it uses a brake pad wear sensor that triggers a separate "Check Brake Pads" message. A worn-pad warning is not the same fault as the ABS light, although the two are often worked on at the same time.
What the Warning Lights and Messages Mean
The GLE owner's manual separates several brake-related warnings. Knowing which one you have tells you how urgent it is.
| Warning | What Mercedes says it means | What to do |
|---|---|---|
| Yellow ABS lamp lit with engine running | ABS is malfunctioning; other driving safety systems may also be off | Drive carefully and have the brake system checked immediately |
| ABS lamp plus a warning tone | EBD is malfunctioning as well | Treat as more serious - brake force distribution control is affected |
| ABS and ESP "Currently Unavailable" | ABS and ESP are temporarily unavailable | Drive carefully above 19 mph (30 km/h) with slight steering movements; if it does not clear, see a shop |
| ABS and ESP "Inoperative" | ABS and ESP are malfunctioning | Have them checked immediately |
| Red brake warning lamp | Brake force boosting malfunction or low brake fluid | Stop safely and do not continue driving |
| "Check Brake Pads" | Pads have reached the wear limit | Replace pads (and the wear sensor) |
The "temporarily unavailable" message is worth understanding. It often means the system could not confirm a plausible sensor signal. The manual's advice to drive gently above 19 mph with small steering inputs lets the system re-check itself. If the message comes back after every drive, treat it as a hard fault, not a glitch.
Common Causes of an ABS Light on the GLE350
1. Wheel speed sensor or its wiring
This is the leading cause on almost any modern vehicle. Brake and Front End, a trade publication for brake technicians, lists wiring faults - broken wires, loose connectors and corrosion - as the most common wheel speed sensor problem. The sensor harness at each corner flexes with the suspension on every bump, and the connectors live in road spray and salt.
2. Debris on the sensor tip
The sensor reads a magnetic field, so metallic dust sticks to it. Material from worn rotors and semi-metallic pads can build up on the tip and weaken the signal until the module flags it. Pulling the sensor, cleaning the tip and the bore, and reinstalling it fixes more ABS lights than people expect.
3. Encoder or wheel bearing problems
Active sensors read an encoder that is often built into the wheel bearing as a ring of small magnets. A damaged encoder, a bearing with excess play, or an encoder packed with debris produces an erratic signal. If the ABS fault always points to the same corner and the sensor and wiring test good, the hub or bearing is the next suspect.
4. Low battery or charging voltage
Electronic control units need stable supply voltage, and a weak 12-volt battery or a charging problem can set several unrelated warnings at once - ABS, ESP and driver-assist messages together. If multiple systems light up at the same time with no brake symptoms, test the battery and charging system before you buy any brake parts.
5. Brake fluid and hydraulic faults
Low fluid shows up as the red brake warning, not the yellow ABS lamp, but a leak can cause both. The GLE manual says to use only brake fluid approved to MB-Approval 331.0 and to renew it at the specified intervals, because fluid absorbs moisture and its boiling point drops over time. A hydraulic unit or control module failure is possible but far less common than a sensor or wiring fault, so rule those out first.
6. ESP software recall (2020-2021)
Mercedes-Benz issued NHTSA recall 21V071 (Mercedes campaign 2021030004) for certain 2020-2021 GLE-Class and GLS-Class vehicles. The ESP software might not meet production specifications, and in certain driving scenarios could apply torque to one front wheel and pull the vehicle to one side. The dealer remedy is a free software update. The recall is not described as an ABS-light fault, but any 2020 or 2021 GLE350 with an ABS or ESP concern should have its VIN checked at mbusa.com/recall before anything is replaced.
How to Diagnose It
- Check for recalls. Run the VIN through the Mercedes recall lookup.
- Read the codes. A basic engine-code reader often cannot see ABS module codes. Use a scan tool that reads the ESP/ABS module; it will name the corner and whether the fault is signal, circuit or plausibility.
- Check the battery. Test resting and charging voltage before chasing brake faults, especially if several warnings appeared together.
- Inspect the flagged corner. Look at the sensor connector, the harness routing along the knuckle and strut, and any sign the wire was stretched or pinched during a previous brake or suspension job.
- Test the sensor the right way. Active sensors cannot be checked with an ohmmeter the way older passive sensors were. Brake and Front End notes they must be connected to the harness with the ignition on to produce a signal; use a scan tool's live wheel-speed data, a voltmeter or an oscilloscope. Compare all four wheel speeds on a slow drive - the bad one drops out or reads erratically.
- Pull and clean. Remove the sensor, clean the tip and bore, and inspect the encoder if you can see it.
The Fix, and What to Replace at the Same Time
A wheel speed sensor is a small bolt-in part: one fastener, one connector and the harness clips. Torque the retaining bolt to the value in the factory service manual. If the fault is in the harness, repair or replace the wire properly rather than twisting splices together, since road water gets into poor splices and the fault returns.
If the fault points to the encoder or bearing, the fix is a hub or bearing replacement on that corner. That job means removing the caliper and rotor, so it is the logical time to inspect the brake rotors and pads on that axle.
Because ABS faults often appear right after brake work, be careful on the next pad job: unclip the sensor harness before moving the caliper, never let the caliper hang on the hose or the sensor wire, and replace the electronic pad wear sensor whenever you replace pads. For the rear axle we carry Bosch ceramic rear brake pads for the 2020-2024 GLE350, and you can browse more ceramic brake pads and brake hardware kits. If you are flushing the fluid, use one that meets MB-Approval 331.0.
The rear brakes also carry the electric parking brake. Follow the service manual procedure for releasing and retracting it with a scan tool before pushing the rear caliper pistons back; forcing them can damage the actuator and set brake warnings of their own.
How Hard Is the Job?
Cleaning or replacing a wheel speed sensor is a beginner-to-moderate job with basic tools once you know which corner is bad - the scan tool diagnosis is the hard part. Harness repairs are moderate. Hub and bearing replacement is more involved: the brakes come off and every fastener needs the correct torque from the service manual. The ESP software update is dealer-only. Whatever the cause, do not ignore the ABS light for months: until it is fixed, the SUV has no anti-lock braking and usually no stability control.
Need the part? Shop Brake Parts at Core Brake Parts
Filter by your exact year, make, and model — every part ships from our Circleville, OH warehouse, free over $75.
Shop Brake Parts →Frequently Asked Questions
Is it safe to drive a GLE350 with the ABS light on?
The normal brakes still work, but Mercedes warns that the wheels may lock during braking, steering and braking are heavily impaired in a hard stop, and other safety systems are switched off. Drive carefully and get it checked promptly. If the red brake warning is also on, stop driving.
Why did the ABS and ESP lights come on together?
Both systems use the same wheel speed sensor signals, so a single sensor or wiring fault disables both. A weak battery can also trigger both at once.
Will new brake pads turn off the ABS light?
No. Worn pads trigger the separate "Check Brake Pads" message. New pads only fix an ABS light if the brake job also repaired a sensor wire or connector that was damaged or left unplugged.
Can I clear the ABS light myself?
A capable scan tool can clear the code, but if the fault remains, the light returns. For the temporary "Currently Unavailable" message, Mercedes advises driving carefully above 19 mph with slight steering movements to let it clear.
Does the 2020-2021 GLE ESP recall cause an ABS light?
The recall covers ESP software that could pull the vehicle to one side in certain maneuvers, and the dealer updates the software for free. Check your VIN at mbusa.com/recall regardless, since it is a free fix on the same system.
What brake fluid does the GLE350 use?
Mercedes specifies brake fluid approved to MB-Approval 331.0, replaced at the intervals in the maintenance schedule.
Sources
- Mercedes-Benz GLE SUV Operator's Manual (MY2021) - ABS, ESP and brake warning lamp meanings, 19 mph self-check advice, Check Brake Pads message, MB-Approval 331.0 brake fluid
- NHTSA recall 21V071 owner notice (Mercedes campaign 2021030004) - 2020-2021 GLE/GLS ESP software recall, concern and free dealer remedy
- Bosch Mobility - Wheel-speed sensor - Hall-effect operation, encoder types, 0.1 km/h detection, signal used by ABS and ESP
- Brake and Front End - Diagnosing Wheel Speed Sensors - active vs passive sensors, wiring as the most common fault, debris on sensor tips, bearing-mounted encoders, testing active sensors
0 comments