Mercedes Won’t Start After Battery Replacement: Ways to Fix

A Mercedes provides reliable service, but it is a machine with numerous parts, and it sometimes fails to function normally. A leading cause of frustration in the automotive industry is when your vehicle will not start even after changing the battery.

Why your Mercedes won’t start:

If your vehicle will not start, it could be caused by a variety of factors. You may have problems starting your vehicle because your starter can’t receive electrical power from the battery, your spark plugs don’t receive power, or you’re having trouble starting because the vehicle has a Drive-Authorization system.

➔ Battery failure

There is an obvious reason for this: the battery might be too old. A majority of vehicle owners would not consider replacing the battery until ten years after purchase, but they should consider replacing the battery as early as six weeks after purchase. Although your battery may be relatively new, if the engine won’t start, use a 12-volt trickle charger to trickle charge your battery.

➔ Circuit breakers and switches

In the event that you find the battery not to be the problem, you should check the fuse for your starter circuit, ignition, EIS, or fuel pump. The fuse is the component that takes the most punishment and is burned out whenever a particular vehicle system malfunctions. You need to swap the fuse with a similar ampere as the original one after testing it with a digital multimeter first.

➔ Switch for the brake light

It is more likely that a malfunctioning brake light switch is the cause of your Mercedes Drive Authorization System not allowing you to start your vehicle.

Module for gear selection:

As soon as you move the shifter from Park to Reverse to Neutral, if you don’t see the gear indicator shift into the letters P, R, and N, then it’s more likely that your gear selector module is defective. Depending on the model of your Mercedes, an OBD1 scanner or OBD2 scanner will display the code on the screen. An engine check can be conducted by using these codes.

Fuel problem:

If you have a fuel pressure gauge, make sure the Schrader valve adapter is attached. A gauge must be connected to the Schrader valve test port after the engine is turned off. Connect the hoses to the engine, and adjust the pressure. In this way, no matter how long you run the engine, the pressure will remain steady. Also, make sure your fuel pump and fuel pump relay are operating correctly. When your ignition is turned to position 2, the fuel pump should run. In this case, the issue lies with your fuel pump. You should also replace the fuel filter as the old one tends to clog up over time.

Methods for fixing:

Following are the solutions for Mercedes that won’t work after a battery replacement.

➔ Jumper cable used to start Mercedes

In the event that your Mercedes breaks down due to a dead battery, the problem can be easily fixed using jumper cables and a healthy battery from another car, or with the use of a battery booster if one is available.

Jumper cable connection method:

In the beginning, you will need to connect the red cable to the positive terminal of the Mercedes dead battery, and then the positive terminal of the donor battery. The black wire should be connected to the negative terminal on the donor battery, then to the bare metal in your Mercedes engine bay. Then begin your Mercedes and the donor vehicle. The cables should be removed in the reverse order.

➔ Clean corrosion from batteries

First you need to remove the cables from your Mercedes battery, which requires no special knowledge or skills, just a bit of concentration, as order is very important.

Corrosion-cleaning method:

Start by removing the black negative cable. The pole clamp can be opened with pliers if it is very tight. Metal pliers are not recommended, but if you do use them, you must be careful not to touch any other parts of the body. Afterwards, you will need to unplug the positive pole cable. The corroded battery can then be cleaned after being removed from the circuit. Connect the terminals once they have been cleaned.

➔ Starter should be fixed temporarily

The engine may start if the starter motor is hit with something like a stick or metal tool, if the engine won’t start because of the starter. If the gears inside the starter are slightly out of alignment or the parts inside are stuck together, this solution works. Nevertheless, you need to have the starter inspected by a dealer or maintenance shop to determine if it is near the end of its useful life.

➔ Diagnose using a scanner

  • Mercedes vehicles are equipped with on-board diagnostics (OBD), which will provide in-depth information on the location of the malfunction.
  • Scanner-based method of diagnosing:
  • The diagnostic tool must first be connected to the Mercedes before you can begin troubleshooting.
  • Under the dashboard, you will usually find the OBDII connector.
  • Turning the ignition on after connecting the wire is a good idea.
  • However, make sure you don’t start the engine.
  • There is then a question about the vehicle that is asked by most diagnostic devices. If you do not enter this 100% correct then the results of the search may be tampered with.
  • It is also common to enter an engine number and a vehicle number in addition to the vehicle model and manufacturer.
  • Always check the accuracy of the information before proceeding with troubleshooting.


A Mercedes that won’t start can be caused by a variety of factors. Even so, we can still fix this problem by implementing different approaches. In this situation, jumper cables may be the best solution. The method for connecting the wires is straightforward.

It’s important to always look for the most obvious cause in triggering a computer malfunction, which would be an empty battery. The best thing for individuals to do in this case is to call a breakdown service or repair shop. In the case of a manufacturer declaring a defect to the customer, the defect can be immediately repaired.


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