How Do I Reset The Mercedes Actros Gearbox?
To reset the Mercedes Actros gearbox, turn the ignition to position "2" so all dash lights come on, press the accelerator to the floor past the kickdown switch and hold it for 8 to 10 seconds, turn the ignition off while keeping the pedal down, then release the pedal slowly and wait 2 minutes before starting the engine. The whole job takes about 5 to 8 minutes. If the gearbox still will not shift properly after the reset, the problem is the oil, the wiring, a sensor or the transmission control unit, not the adaptation.
The Mercedes-Benz Actros is a heavy-duty truck that replaced the SK. According to Mercedes-Benz Trucks, it premiered at the IAA Commercial Vehicles show in 1996, and it is used for long-distance haulage, heavy distribution and construction work. Like any truck it has weak spots, and gear selector problems are one of the issues Actros owners run into.
TL;DR
- Symptom: gearbox in limp mode, stuck in 2nd or 3rd, or gears not selecting.
- Reset: ignition to "2", accelerator to the floor for 8 to 10 seconds, ignition off, release, wait 2 minutes.
- Time: about 5 to 8 minutes.
- If the reset fails: check transmission oil level and condition, then the electrical connectors.
- Near 50,000 miles: the oil and filter are due, which can cause the same shifting faults.
- Still faulty: solenoids, speed or selector sensor, or the transmission control unit need a diagnostic.
If this is not your case, read How to reset Mercedes transmission?.
Table Of Content
- How does the Mercedes Actros gearbox work?
- What problems does the Mercedes Actros gearbox have?
- How do you reset the Mercedes Actros gearbox?
- How do you fix Mercedes Actros gear shifting issues?
- What if the Actros gearbox itself is faulty?
- Conclusion
1. How Does The Mercedes Actros Gearbox Work?
The Actros is powered by a turbocharged, intercooled inline-6 diesel and comes in weights starting at 18 tonnes. Daimler Trucks introduced Actros version II in 2002 and version III in 2007. The fourth generation, called "the New Actros", arrived in July 2011.
From the start, the Actros used an automated gear selection system. Mercedes-Benz Trucks describes the original 1996 Telligent shift system as one of the first (semi-)automatic shift systems, choosing the right gear for the driving situation. Five different 16-speed gearboxes were offered, each matched to the engine output for good gradability and low manoeuvring speeds, and combined with application-specific drive axles to get the engine's power to the wheels with as little loss as possible. On the current Actros L, Mercedes pairs the OM 471 engine with the G 291 transmission and PowerShift Advanced, quoting 4% lower fuel consumption for that drivetrain.
The system is a small lever under the right armrest with a flat switch underneath. The lever is tilted slightly to match the natural curve of the driver's hand, and there are buttons on each side of it.
When the truck is stopped, the driver presses the right button, pushes the lever forward (while holding it) and releases it to select fourth fast. The current gear shows as a large number on the main display.
The driver then presses the clutch pedal and waits about 2 seconds. A double click sounds through the speakers when the shift is complete, and the driver pulls away as usual.
On the move, the driver has two options: use the splitter switch (the small switch under the lever) to pre-select gears, or push or pull the lever and let the computer choose the gear.
Either way, the gear is selected first and then the clutch is pressed. For example, pulling the splitter switch up once in fourth fast pre-selects fifth slow.
To select neutral, press the left button (the "flush button", because it sits flush with the lever).
2. What Problems Does The Mercedes Actros Gearbox Have?
Some gear selector problems come from poor maintenance, others from component failures or factory faults. Typical causes are a wrong transmission oil level, a faulty primary pump, water in the system, oil slippage and other failing parts.
The result is that the transmission goes into "limp mode" and stops shifting properly. Instead it holds the next available gear, usually second or third. Limp mode protects the transmission from more damage, but driving in it for too long can cause damage of its own.
| Problem | Likely cause | What to do |
|---|---|---|
| Limp mode, stuck in 2nd or 3rd | Lost adaptation or a detected fault | Do the reset in section 3, then read the fault codes |
| Shifting faults near 50,000 miles | Old oil and filter | Change the transmission oil and filter |
| Dark or black transmission oil | Worn or overheated oil | Replace the oil and filter |
| Faults after rain or washing | Water in the system or corroded connectors | Dry and clean connectors with contact cleaner |
| Gears will not select at all | Faulty solenoid, speed or selector sensor, or control unit | Dealer diagnostic, then repair or replace the part |
3. How Do You Reset The Mercedes Actros Gearbox?
The reset is simple and takes about 5 to 8 minutes:
- Open the driver's door and get in.
- Turn the ignition to position "2". All the dashboard lights should come on at the same time.
- Press the accelerator all the way to the floor so the kickdown switch is activated.
- Hold the pedal down for 8 to 10 seconds.
- Turn the ignition key off, but leave it in the ignition.
- Take your foot off the pedal slowly.
- Wait 2 minutes.
- Start the engine. The gearbox is now reset.
This resets the communication between the throttle and the transmission. If it does not help and the truck is approaching 50,000 miles, the transmission is due a service: the oil and filter need replacing.
4. How Do You Fix Mercedes Actros Gear Shifting Issues?
Start with the transmission oil. Check its colour: it should be dark red. If it is black, replace it along with the oil filter.
Then check the level while the gearbox is still warm. Move the selector through all the gear positions, holding each for a few seconds, before returning to the start position.
If needed, top up through the dipstick tube. Use the correct oil: this matters on the Actros, because fluid specifications differ between vehicles, and the manufacturer may advise switching to a different fluid type.
Confirm the right fluid with your local Mercedes-Benz Trucks dealer or parts department. If the oil is fine, check the gearbox's electrical connections and spray each connector with contact cleaner. A fault code reader helps narrow down which part is reporting the fault.
5. What If The Actros Gearbox Itself Is Faulty?
If the transmission stays in limp mode and the gears still will not shift correctly, the gearbox itself may be at fault. The cause is hard to find on your own, so take the truck to an authorised dealer or a specialist. Their diagnostic equipment can pinpoint the problem and the best way to fix it.
An electrical fault is most likely a faulty solenoid, a damaged speed or selector sensor, or the transmission control module itself. Voltage overload, water in the system, heat stress and general vibration can all damage these modules.
Replacing the module can be costly and slow. If the transmission itself is damaged, it must be replaced (which is very expensive) or rebuilt. Sometimes the problem is smaller and only the control unit needs replacing. For comparison with Mercedes vans, see Mercedes-Benz Sprinter transmission issues.
6. Conclusion
A diesel engine turns much faster than the drive wheels need to, so the gearbox reduces the speed to pass power to the wheels. Its range of ratios covers starting from rest, climbing hills and cruising on the flat: the lower the gear, the slower the wheels turn compared with the engine. When the Actros gearbox misbehaves, try the reset first, then the oil, then the wiring, and leave internal faults to a dealer.