The ‘A Class’ is German car manufacturer Mercedes-Benz entry level vehicle and has been in production since 1997. The following Mercedes A Class dashboard warning lights is a guide for version W177, 2018 onwards and will display a symbol with its meaning along with the recommended action to take. Many of the warning lights below, along with remedial action will apply to other versions of the Mercedes A Class.
If the ABS warning light illuminates while driving, it means the Anti-lock Braking System has failed. If an additional warning tone sounds, it means the EBD is malfunctioning. EBD stands for Electronic Brakeforce Distribution and is s system that improves the Mercedes A Class braking ability by distributing brakeforce to individual wheels. where needed the most.
If the ABS and EBD is malfunctioning, there’s a risk that the wheels may lock during braking. One of the most common reasons for ABS failure is due to one of the vehicle’s wheel speed sensors malfunctioning.
ESP stands for Electronic Stability Program and is a system that adjusts brake force and engine power to help reduce understeer and oversteer for the Mercedes A Class. The system also incudes a traction control program which aims to reduce wheel slip. Drive carefully on a suitable stretch of road, making slight steering movements at a speed above 30 km/h. If both ABS and the ESP warning light illuminate, it may indicate a problem with other safety systems such as BAS (Brake Assist).
In addition to ABS and ESP, the EBD warning light may illuminate. EBD stands for Electronic Brakeforce Distribution and is a system that distributes brakeforce to individual wheels that require it the most. As with ABS, a common reason for these issues is due to a faulty wheel speed sensor.
If the engine warning light is also on ESP may be automatically disabled . This is usually due to the reduced engine power safety system that disables ESP to prevent the program for interfering with vehicle driveability. For more information, see What ESC is in Cars and How Does ESC Work in Cars.
The red oil light can come on as an indication that there is insufficient oil in the engine, or that there is low oil pressure. A message will accompany the warning light.
- ‘Add 1 litre engine oil when next refuelling‘. Depending on driving style, the vehicle consumes up to 0.8 litre of oil per 1000 km. You can check oil levels after 30 minutes of driving and by accessing the onboard computer: Services > Engine oil level.
- ‘Engine oil level Reduce oil level‘. This is when too much oil has been added. Reduce engine oil levels to avoid engine damage.
- ‘Engine oil level Stop vehicle Switch engine off‘. This warning message comes on because continued driving will cause engine damage due to lack of oil.
- ‘Engine oil pressure Stop Switch off engine‘. Engine oil pressure too low. Avoid driving, contact Mercedes workshop.
- ‘Engine oil level cannot be measured‘, or ‘Engine oil level System currently unavail‘. The engine oil level sensor has malfunctioned.
Tyre Pressure Symbol
The Mercedes A Class tyre pressure warning light will either:
- Illuminate to indicate a tyre pressure loss
- Flash for one minutes, then remain steady lit to indicate a failure with the Tyre Pressure Monitoring System (TPMS)
The TPMS checks the tyre pressure and the tyre temperature of the tyres fitted to the vehicle by means of a tyre pressure sensor. After altering tyre pressures, in most cases the tyre pressure monitoring system will automatically reset to the new reference values, but you can manually reset the tyre pressure monitoring system if you prefer. Adjust tyre pressures when cold. You may need to reset the tyre pressure monitoring system under the following conditions:
- Tyre pressures have changed
- The vehicle’s wheels or tyres have been newly changed
Reset the Tyre Pressure Monitoring System
To reset the Mercedes A Class tyre pressure monitoring system, on the on-board computer, select:
- On the Touch Control function on the left side of the steering wheel, swipe down.
- You’ll see the following message: Use the current pressures as new reference values?
- To reset the tyre pressure monitoring system, press Touch Control on the left side of the steering wheel.
- The message: Tyre press. monitor restarted will be displayed.
After driving for a few minutes, the TPMS checks whether the current tyre pressures are within the specified range. The current tyre pressures are then accepted as reference values and monitored.
Why is My Mercedes A Class Tyre Warning Light Flashing?
The most common reasons for a flashing tyre pressure warning light include:
- A tyre has been fitted that does not contain a sensor
- The battery inside a sensor has expired
- Wheels of tyres have been fitted that do not comply with the manufacturer’s recommendations
- A sensor has been damaged while changing tyres
- Radio frequency interference between sensor and receiver
Electrical Fault / Battery Symbol
If the red battery warning light remains lit or comes on while driving, it means there’s a fault with the Mercedes A Class electrical system. It may also mean that there has been a high electrical load and the battery charge is low.
Certain vehicle safety function may not operate as expected with a low battery charge. As such, you may receive a message to stop the vehicle and leave the engine running to charge the battery.
If the battery light remains on after stopping with the engine on, Mercedes recommends that you do not continue driving and contact a Mercedes workshop. A common cause for the battery not charging is a failing alternator, or alternator drive belt. See why is my car battery warning light on for further information.
The red airbag warning light will illuminate, along with a message indicating that the airbag / seat belt tensioner system has a fault. The fault may occur in the following:
Vehicle Front Impact
- Driver’s airbag, front passenger airbag
- Knee airbag
- Seat belt tensioner
- Window airbag
Vehicle Side Impact
- Seat belt tensioner
- Side airbag
- Window airbag
Vehicle Rear Impact or Rollover
- Seat belt tensioner
- Window airbag
When the airbag warning light remains lit, components in the restraint system may be activated unintentionally or not deploy as intended in an accident. Reasons for the warning light can include cables and connection under front seat loose, crash sensor fault, airbag clock spring, collision damage.
The key symbol may illuminate in white, yellow or red and will display a corresponding message along with the symbol. The following messages can apply:
- Replace key: Have the vehicle key replaced.
- Change key batteries: The key battery is discharged and required replacing.
- Key not detected: Change the location of the key inside the vehicle, or place the key in the key slot. If the key symbol is red, ensure that the key is inside the vehicle.
- Key being initialised please wait: Wait until the process is complete.
- Place the key in the marked space: Change the location of the key inside the vehicle, or place the key in the key slot.
Defective Lights Symbol
The defective lights symbol will come on along with a warning message. The following warning messages can apply:
- Left dipped beam (example): Check whether you’re able to replace the specified light source yourself, or contact a Mercedes workshop.
- Malfunction: General exterior lights fault. Check fuses and replace if necessary.
- Automatic driving lights inoperative: The light sensor for the automatic driving lights has a fault and requires replacement.
- Active light system inoperative: The active headlights have a fault.
- Switch on headlamps: You’re driving without low-beam headlamps.
- Intelligent light system inoperative: The vehicle’s intelligent light system is malfunctioning. The lighting system continues to function properly without the functions of the Intelligent Light System.
- Adaptive high beam assist currently unavailable See Owner’s Manual: Operate high beam manually until the system is available again.
Stationary Heater Symbol
This symbol illuminates when there’s a problem with the Mercedes A Class stationary heater. Along with the warning light, you’ll receive a corresponding message:
- Inoperative see owners’ man.: This means there’s a temporary malfunction with the stationary heater. When the vehicle is stationary on a level surface and the engine has cooled down, make up to four attempts to switch on the stationary heater, waiting several minutes between each attempt. If the stationary heater fails to switch on, contact a Mercedes workshop.
- Inoperative battery low: The on-board electrical system voltage is too low and the stationary heater has switched off. Once the battery is sufficiently charged (driving for an extended distance), the stationary heater system will resume.
- Inoperative refuel vehicle: Too little fuel in the tank. Refuel the vehicle.
- Vehicle is operational switch off ignition before exiting: The vehicle is being left in a ready-to-drive state. Switch off the vehicle ignition, secure the vehicle and take the key with you.
Yellow Triangle Symbol
The Mercedes A Class yellow triangle warning light containing an exclamation mark illuminates along with the message: ‘Vehicle is operational switch off ignition before exiting’. This is a reminder for when you leave the vehicle, switch off the ignition, secure the vehicle from rolling and take the key with you.
If you are remaining inside the vehicle, switch off any electrical consumers such as the seat heating else the 12v battery may discharge and starting the engine may not be possible.
The trailer warning light illuminates with the message: ‘Check trailer hitch lock’. In this situation, safely stop the vehicle, uncouple the trailer and secure it from rolling. Initiate a new swivel movement and do no re-couple the trailer until the trailer warning light goes off.
Power Steering Symbol
The steering wheel with exclamation mark indicates a fault with the power steering system. Along with the warning light, you may receive the following messages:
‘Steering malfunction Increased physical effort See Owner’s Manual’
This means that power steering has failed partially or completely, but you can continue driving. This can often be attributed to a temporary issue due to the power steering motor overheating. Overheating can occur when steering is intensive when the vehicle is stationary.
‘Steering malfunction Stop immediately See Owner’s Manual’
This means the power steering has malfunctioned and it may be dangerous to continue driving. Pull off the road, stop the vehicle and contact a Mercedes workshop.
‘Steering malfunction See Owner’s Manual’
This message means the electric steering lock is malfunctioning and it may be dangerous to continue driving. Pull off the road, stop the vehicle and contact a Mercedes workshop.
Steering Lock Symbol
This symbol illuminates with the warning message: ‘Before starting the engine, turn the steering wheel.’ It means the electric steering lock could not unlock the steering. Switch off the ignition and move the steering wheel to the left and right to unlock the steering.
Add Coolant Symbol
If this symbol illuminates on your Mercedes A Class dashboard, it means the engine coolant is low and requires topping up. To add coolant:
- Park the vehicle on a level surface.
- Check the coolant temperature display in the instrument cluster. The coolant temperature must be below 70°C.
- Slowly turn cap (1) anti-clockwise to release overpressure. Continue turning cap (1) anti-clockwise and remove it.
The coolant level is correct in the following cases:
- If the engine is cold, the coolant is up to marker bar (2).
- If the engine is warm, the coolant is up to 1.5 cm over the marker bar (2) .
Engine Coolant Too Hot Symbol
This red warning symbol illuminate when the engine coolant is too hot and the engine is overheating. You’ll also see the following message: ‘Coolant Stop vehicle Switch engine off’. Stop the vehicle as soon as safely possible and switch off the engine.
Before opening the bonnet, allow the engine to cool. There may be a malfunction in the engine cooling system. When engine has cooled, add engine coolant (see above). For further information on what to do, see red engine coolant warning light on or flashing. Possible reasons for the red engine coolant light can include:
- The temperature sensor is malfunctioning
- The coolant level is too low
- The air supply to the radiator is obstructed
- The radiator fan is faulty
The engine coolant light may also come on in yellow. The possible reasons for a yellow engine coolant warning light can include:
- The temperature sensor is malfunctioning
- The charge air, transmission oil or battery cooling is faulty
- The radiator shutters are blocked or defective
Engine Warning Symbol
The Mercedes A Class engine warning light comes on when the onboard diagnostic system has detected a fault with the emissions control system. You can usually continue driving when the engine light comes on, but if the symbol begins to flash, it may indicate an engine misfire which can cause damage. Reduce speed and avoid high engine speeds.
There are many components that make up the emissions control system and as such, diagnostics is required. A vehicle workshop will connect diagnostic equipment to read fault codes, which will help to localise the problem area. A fault code is usually generated when the engine light comes on. For reasons why the engine light is on and what to do, see reasons why the engine warning light is on.
Fuel Filter Symbol
This warning light illuminates indicating that the fuel filter is clogged or that there’s water in the fuel filter that requires draining.
Air Filter Symbol
This warning light illuminates indicating that the engine air filter is saturated / dirty and needs to be replaced. The air filter is locate din the compartment just to the left of the windscreen washer reservoir.
This warning light illuminates when the transmission is overheating. The warning message: ‘Trans. oil overheated drive on with care’ may also be seen. Drive at a slow engine speed. Avoid a sporty driving style, if possible, avoid uphill gradients until the warning light goes off.
Parking Brake Symbol
The red electronic parking brake warning light illuminates to indicate the parking brake is applied. If the yellow warning light comes on, comes on along with the red warning light or if the red parking brake flashes, it means the electronic parking brake has malfunctioned.
This may indicate the 12v battery has a low state of charge. Switch the ignition off and on again and operate the electronic parking brake manually. If the red parking brake symbol flashes but the yellow symbol is not illuminated, it means conditions for automatic release of the parking brake have not been met.
The red brake symbol means that either there is insufficient brake fluid in the reservoir, or that the brake force boosting has malfunctioned. Check brake fluid levels. If levels are sufficient, brake force boosting may not be working as expected. You may be required to press the brake pedal with more force. Avoid driving an contact a Mercedes workshop. Mercedes advise that you do not top up brake fluid and to contact their workshop.
A yellow symbol means the brake system has a minor malfunction, but you can continue driving. Have the brake system serviced as soon as possible.
Brake hold assist continues to apply the vehicle’s brake once the driver has braked to a complete stop. It means the driver can release their foot from the brake pedal without the vehicle rolling. If the HOLD warning light comes on, it means the vehicle is rolling, or conditions for brake hold assist have not been met.
Active Brake Assist Symbol
The red triangle alert symbol lights up when the vehicle is in motion, informing the driver that they are too close to the vehicle in front, or approaching an obstacle at too higher speed. In the latter case, a audible warning alert will sound. Increase your distance or be prepared to brake immediately.
The Mercedes A Class has many sensors located around the vehicle. If you have any of the following warning light that illuminate, ensure that the sensors around the vehicle are clean. The following system rely on sensors:
- Adaptive Cruise Control
- Active Blind Spot Assist
- Active Lane Keeping Assist
- Active parking Assist
- Active Distance Assist
- Active Speed Limit Assist
- Active Steering Assist
- Active Lane Changing Assist
- Active Brake Assist
- Cross-traffic function
- Evasive Steering Assist
- High Beam Assist
The following locations are where the various sensors are located on the Mercedes A Class
- Multifunction camera
- Cameras in the outside mirrors
- Front radar
- Front camera
- Corner radars
- Ultrasonic sensors
- Reversing camera
On your Mercedes A Class dashboard, you may receive a warning message but without a warning light. The possible warning messages and remedial action are as follows:
|Warning Message||Remedial Action|
|Front-passenger airbag disabled See Owner’s Manual||Make sure that no objects are trapped under the front passenger seat and check the status of automatic front passenger airbag actuation.|
|Place the key in the marked space See Owner’s Manual||Change the location of the key in the vehicle or place the key in the slot for starting the engine with the key.|
|Adaptive High Beam Assist currently unavailable See Owner’s Manual||Continue driving. Operate the high beam manually until Adaptive High Beam Assist is available again.|
|Head-up display currently unavailable See Owner’s Manual||Stop the vehicle when safe to do so and switch the ignition off and on again.|
|To switch off the engine, press the Start/Stop button for at least 3 seconds or 3 times||You have pressed the start/stop button while the vehicle is in motion.|
|Cannot start engine See Owner’s Manual||Switch the ignition off and switch it back on.|
|Only select Park (P) when vehicle is stationary||Press the brake pedal to stop the vehicle. It is possible to select the park position (P) only if the vehicle is stationary.|
|Apply brake to deselect Park (P) position||You have attempted to shift the transmission out of park position (P) and into another transmission position. Depress the brake pedal. Select transmission position D, R or neutral N|
|To shift out of P or N, depress brake and start engine||You have attempted to shift the transmission out of park position P or neutral N and into another transmission position. Depress the brake pedal. Start the vehicle. Change the transmission position.|
|Apply brake to select D or R||You have attempted to select transmission position D or R. Depress the brake pedal and select transmission position D or R.|
|Apply brake to select R||You have attempted to select transmission position R. Depress the brake pedal and select transmission position R.|
|Risk of vehicle rolling Driver door open and transmission not in P||The driver’s door is not fully closed and transmission position D, R or neutral N is selected.
The vehicle may roll away. Select park position P when switching off the vehicle.
|N permanently active Risk of vehicle rolling||Neutral N has been selected while the vehicle is rolling or while you are driving. Depress the brake pedal to stop, then shift the transmission to park position P while the vehicle is stationary.|
|Without changing gear, consult workshop||The transmission is malfunctioning. It is no longer possible to change the transmission position.
If transmission position D is selected, consult a qualified specialist workshop and do not change the transmission position.
|Reversing not poss. Consult workshop||The transmission is malfunctioning. It is not possible to select transmission position R. Consult a qualified specialist workshop.|
|Transmission Malfunction Stop||The transmission is malfunctioning. The transmission shifts to neutral N automatically. Stop the vehicle when safe to do so. Depress the brake pedal. Engage park position P.|
|Transmission Malfunction||The transmission is malfunctioning. The cause could be an overheated clutch or blocked gears. Let the transmission cool down. Reduce speed and engine load. If the display message still appears following a restart, consult a qualified specialist workshop|
|Parking lock inoperative Apply the parking brake||The transmission is malfunctioning. The park position P cannot be selected. Park the vehicle safely and use the electric parking brake to secure the vehicle against rolling away.|
|Teaching in transmission Operate selector lever Brake for XX seconds Risk of vehicle rolling||The transmission is being taught in. There is a risk of the vehicle rolling. Depress and hold the brake pedal until the teaching process has been completed. The electric parking brake is also applied automatically during the teaching process. Switch on the ignition. Select park position P, transmission position R or neutral N. Once complete, you’ll receive the message: ‘Teaching in transmission complete’.|
|Risk of vehicle rolling away
Apply parking brake
See Owner’s Manual
|The transmission position cannot be reliably identified. Use the electric parking brake to secure the vehicle against rolling away.|
|Clutch overheated Avoid pulling away until the warning goes out||The clutch is under considerable load and is overheating. Avoid frequent pulling away and driving at walking pace over longer distances. Stop the vehicle, paying attention to road and traffic conditions, and leave the engine running. The clutch will cool more quickly when the engine is running.
Continue driving at a steady speed and remove your foot from the clutch pedal. Do not let the clutch drag. The clutch will cool while the vehicle is in motion. When the clutch has cooled down, the display message will disappear.
|Tyre press. monitor currently unavailable||There is interference from a powerful radio signal source. As a result, no signals from the tyre pressure sensors are being received. The tyre pressure monitoring system is temporarily unavailable.
The tyre pressure monitoring system will restart automatically as soon as the cause has been rectified.
|Tyre press. monitor inoperative No wheel sensors||The wheels fitted do not have suitable tyre pressure sensors. The tyre pressure monitoring system is deactivated. Fit wheels with suitable tyre pressure sensors.|
|Active Brake Assist Functions limited See Owner’s Manual||The following functions may be temporarily unavailable or only partially available:
Restarting the vehicle should rectify the problem. If the problem persists, contact a Mercedes workshop.
|Parking Assist and PARKTRONIC inoperative See Owner’s Manual||Restarting the vehicle should rectify the problem. If the problem persists, contact a Mercedes workshop.|
|Active Lane Keeping Assist currently unavailable See Owner’s Manual||Active Lane Keeping Assist is temporarily unavailable. The ambient conditions are outside the system limits. As soon as the ambient conditions are within the system limits, the system will become available again.|
|Active Blind Spot Assist / Blind Spot Assist inoperative||Restarting the vehicle should rectify the problem. If the problem persists, contact a Mercedes workshop.|