MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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In this guide (7 sections)
Watch: Mercedes-Benz Jump Start GLA-Class with Dead Battery
Top 3 jump starters for a Mercedes-Benz
- Noco Genius Boost GB40 Ultra Safe Lithium
- Gooloo 600 Peak Jump Starter Power Bank
- Stanley JC509 1000 Peak AMP with Air Compressor
4 tips on how to safely jump start a Mercedes-Benz
Jumpstarting a Mercedes-Benz can be a nerve-wracking experience and, if performed incorrectly, an expensive mistake. We have seen many Mercedes-Benz vehicles with damaged electronics or additional fault codes due to improper jump-starting. It is common for warning lights to light up your dashboard after you jump-start your Mercedes-Benz. In this article, we share some tips to help you avoid unnecessary problems and repairs.
Before the tips: the order the clamps go on
Everything below is about protecting the electronics. This part is about protecting you, and the article would be incomplete without it, because the order the clamps go on and come off is the whole of jump start safety.
A lead acid battery gives off hydrogen. A spark at the battery can ignite it. That is the entire reason the last clamp does not go on the dead battery.
- Red clamp to the positive terminal of the dead battery, which on most of these cars is the covered jump start post described in Tip 1.
- Other red clamp to the positive terminal of the good battery or the jump box output.
- Black clamp to the negative terminal of the good battery or the jump box.
- Last black clamp to bare metal on the dead car, the designated negative post beside the jump terminal or a solid engine or chassis ground. Not the dead battery negative post.
Disconnect in exactly the reverse order, ground clamp off first.
While you work: keep the four clamps from touching each other or any metal, because that arcs. Never ground to anything that is part of the fuel system. And if the battery is frozen, stop. A battery with frozen electrolyte must be thawed indoors before anyone puts a charger or a jumper cable near it.
One more reason the last clamp belongs on a ground point rather than the battery post on these cars in particular: on any Mercedes-Benz whose battery sits in the trunk or under the rear seat, a battery sensor is clamped to the negative post, and clamping a jumper onto it can damage the sensor.
Tip 1: Use the dedicated jump-start terminals
Most Mercedes-Benz models, such as the E, C, S, CLK, ML, CLA, GL, and G Class, have a positive battery terminal in the engine bay designed specifically for jump-starting. The terminal is covered with a red plastic cover marked with a (+). Â This terminal should be used to jump-start a Mercedes-Benz whenever possible. Right next to it, there is a post for you to connect the negative clamp. This adds a layer of protection in case you incorrectly connect the jumper cables.
Tip 2: Disconnect and charge the battery whenever possible.
If your situation permits, it is better to disconnect the battery terminals and charge the battery separately before you try starting the Mercedes-Benz. By fully charging the battery before you start the car, you will avoid triggering unnecessary warnings and fault codes. It is less likely to cause damage to electronic components as well. Warnings such as Low Battery Voltage and SRS Airbag Malfunctions can be triggered when jump-starting an MB since the battery takes a while to charge. This can be avoided if you charge the battery before you start your car. If you have a completely discharged battery that is relatively new, we recommend charging it using a 2 amp trickle charge to bring the battery back to life. We frequently use a Black and Decker 12 volt Trickle Charger to charge the Mercedes-Benz battery. Remember that when using this method, you must charge the battery for at least 12 hours.
Tip 3: Use a jump starter that provides reverse polarity protection.
If you are stranded in a parking lot, you may have no option but to jump-start your Mercedes-Benz on the spot. With hundreds of jump starters on sale, you may wonder what’s the best jump starter for Mercedes-Benz cars.  We recommend using a jump starter that provides reverse polarity protection. These mistake-proof jump starters allow you to safely connect to any battery and minimize potential damage to those expensive electronics and control units found on Mercedes-Benz cars.
The Noco Genius Boost GB40 provides ultra-safe spark-proof technology and reverse polarity protection. This model provides 1000 Max Amps and enough cold cranking amps to jump-start even eight-cylinder Mercedes-Benz engines, and yes, it can fit in your glove box. The YOUCANIC Pro 6000A Jump Starter is also an excellent choice for a quick boost.
Tip 4: MB Medic 2×10 minute rule
Do you have no option but to jump-start a Mercedes-Benz right there and then? Follow this rule to minimize the occurrence of unnecessary low-voltage fault codes.
What is the MB Medic 2×10-minute rule?
MB Medic 2×10 minute rule
Step 1: Connect the jumper cables or jump box to your dead Mercedes-Benz battery and let it charge for at least 10 minutes before the jump start. Not only do you start the battery recovery/charging process, but it will be easier to crank the engine. Otherwise, you may only hear a click, and the engine won’t turn over.
Step 2: Keep the jumper cables connected for another 10 minutes after you start the car. The jump box will provide power for your Mercedes-Benz if the main battery voltage is still low. In the meantime, the main battery continues to get charged.
What the warning lights after a jump start actually mean
The intro promises this page will help you avoid warning lights, so it is worth finishing the thought. After a jump start on a deeply flat battery you will often get a cluster full of them: ABS, ESP, SRS, sometimes transmission and air suspension together.
Most of those are not faults. They are the record of what the modules saw while the voltage was on the floor, and a module that briefly lost its supply logs a fault whether or not anything is broken. The 2×10 minute rule above exists to reduce how many get logged in the first place.
The part that trips people up is that the lights do not always clear themselves. Stored faults stay stored. So after the car is running and the battery is properly charged, the sequence is: clear the codes, drive it, then re-scan. What comes back on that second scan is real. What does not come back was just the low voltage event.
Without that step people replace parts to chase lights that were already history, which is the expensive version of this problem and the one worth avoiding.
What you need to clear them
A basic OBD-II reader will not do it. It reaches the engine control unit and nothing else, so it cannot see or clear the ABS, SRS, ESP or transmission codes a jump start leaves behind, which are exactly the ones lit on your dashboard.
The YOUCANIC UCAN-II Pro reads and clears across those modules, and it shows battery voltage as a live value, which is useful here for a reason the lights do not tell you: if voltage is still sagging with the engine running, the problem is the charging system or a battery that will not hold charge, and no amount of clearing codes will fix that. A jump start that has to be repeated every morning is a battery or alternator question, not a code question.
If a module did not survive the jump start
This is the outcome the whole article is written to prevent, and occasionally it happens anyway, usually from reversed polarity. The intro is right that it is an expensive mistake.
Before accepting a quote for a replacement unit, it is worth knowing that a replacement has to be coded to the car, while a board level repair of the original does not, so the coding and adaptations stay as they are. Module Medics repair control units at board level and return the original.
The honest caveat: confirm the module is genuinely damaged first. A module reporting an undervoltage fault is doing its job correctly, and the clear and re-scan cycle above is how you tell a damaged unit from one that merely remembers a bad morning.
Related reading
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
