Stop Vehicle Leave Engine Running – What Does It Mean?

From blinking lights to beeping sounds and error codes, our vehicle warns or alerts us in different ways. I am certain you are familiar with some of these alerts, like the blinking engine lights, seat belt beeping sound, and even the low oil light. These are all common. But depending on how sophisticated your vehicle is and what type of vehicle you drive, you may get to see some alerts or warning messages that are not so common. 

A typical example is the “stop vehicle leave engine running” message, which is peculiar to Mercedes Benz. If you don’t own a Mercedes Benz, chances are that you may never see this alert, but if you do and have seen this message pop up on your dashboard, then here is all you need to know about it. 

Why is my car saying stop vehicle leave engine running?

If you see this message displayed on your car’s dashboard, it is a signal that something is wrong with the battery. What this means is that the current charge on your car’s battery is low (likely dropped below 12.5 volts), and the battery can no longer carry out its functions properly. The battery plays a central role in the operation of the vehicle. All electronic components of the car are powered by the battery. This includes the sensors, spark plugs, injectors, etc., and everything your car needs to operate smoothly. 

Ordinarily, the battery should not have any problem carrying out these functions since it is backed up by the alternator. But sometimes it happens that the battery can’t keep up with the power demands. In that case, the car’s electronic system will alert you to the state of your battery with clear instructions to follow to prevent your car from completely shutting down in the middle of the road.

What should you do when you see this warning?

If you take a look at the complete message, you will see that it is a very precise instruction for the driver to follow. First, “stop the vehicle” means stop driving (but don’t turn the car off as the battery might not have enough charge to start the car).  “Shift to P” (put the vehicle in Parking mode), and then “leave the engine running,” meaning idling the engine. 

Now here is why you need to follow this instruction. Since the battery is low, obviously, it needs to recharge. I know the first question most of you would be asking by this time is, Isn’t the battery meant to be charging while you are driving?” well…I’ll address that soon. So when you park the car, you leave the engine idling for some minutes to recharge the battery.

As soon as the battery is sufficiently charged, the message should disappear. While idling the engine, you should also ensure that any other electrical or electronic component is turned off so that the battery can charge as quickly as possible.

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What are the main causes?

The stop engine leave vehicle running is a temporary fix to the problem. Following the instructions gives your battery time to recharge before using it again. But this is not how it is supposed to be. Usually, the battery should not discharge so much that the vehicle needs to stop. As I mentioned earlier, the alternator is always supplying current to charge the battery, so it never runs out. If you ever get to see this message, then there is an underlining cause that should be fixed immediately. With that being the case, here are the most common causes of this problem. 

Bad battery

The stopped vehicle leave engine running is a tale-tale sign that everything is not okay with your battery. This could be with the battery connectors or the battery itself. Loose connectors will create a partial contact that will disrupt the current flow from the battery. All you need to do in this case is tighten the battery connectors. On the other hand, if the issue is with the battery, it might need to be replaced. 

On average, a car’s battery has a lifespan of 3 – 5 years. How long your car’s battery will last depends on several factors, including how it is used and environmental conditions. When the battery is no longer performing optimally, it will not be able to hold as much charge as it used to. A common sign of a degraded battery is difficulty starting the car in the morning or frequent shutdown. 

But thanks to advanced technology, your car will likely warn you if things get so bad when you are driving to prevent a sudden shutdown. If you see the stop vehicle, leave engine running message, the first thing to do is test your car’s battery. Anything below 12 indicates a weak battery that might need to be charged or replaced. 

Faulty alternator

Of course, if the battery is not being supplied with any current from the alternator, it won’t charge. If that is the case, it is only a matter of time before the battery is completely drained. The alternator converts mechanical energy into electrical energy, which it uses to recharge the battery. When the alternator is working correctly, then following the message prompt will give it enough time to recharge the battery. But if the alternator is faulty and not producing current, then it wouldn’t be able to recharge the battery even if you follow the instruction on the dashboard. The best thing to do in such a situation is to get the alternator repaired or replaced. 

Excessive power draw (too many accessories drawing power)

The modern car dashboard is an advanced hub that can connect to multiple devices such as phones, iPad (for maps), mp3 players, and many other electronic components. But these accessories can be detrimental to your battery. The reason is that most of them rely on the car’s battery to power up. A common example is a mobile phone. Most people make a habit of charging their phones in the car. This isn’t bad but imagine if there are about 4 or 5 people who are all charging their phones. At the same time, other accessories like radio, AC, headlights, etc are all turned on. This can draw a significant amount of power from the battery resulting in the stop vehicle leave engine running alert. 

Parasitic drain

When you turn off your car, not every accessory is turned off. Some important components constantly draw power from the battery to stay awake. This is quite normal, an example is the car security system. Usually, this wouldn’t have so much impact on the battery. But if the car’s electrical system has a fault, other systems or components that should otherwise be turned off will remain on. Thereby drawing more power (than usual) from the battery. Parasitic drains may be difficult to rectify because there are likely symptoms of a faulty electrical system which warrants a visit to your mechanic.

Having the radio and lights on with the engine switched off

Whether you are waiting in a queue, in the parking lot, or you are enjoying the scenic view of the sunset, you may want to listen to your radio or play your favorite song. At this time, it is perfectly normal to turn off your car’s engine (leaving the radio on). Some people also leave the headlights on to give a little light to their surrounding while they chill. Well, these few minutes of extra power can drain your battery, especially if it is already getting old and can’t hold a charge for too long. If you noticed the “stop engine leave vehicle running” message after doing the above, you’ll need to replace your battery soon. 

Faulty voltage regulator

The voltage regulator is a device that regulates the voltage produced by the alternator, ensuring that the right amount is sent to charge the battery. So it acts like the gatekeeper between the powerful alternator and the sensitive components of your car. Like every other car component, the voltage regulator goes bad from time to time and needs to be replaced. One of the signs of a faulty voltage regulator is that the battery wouldn’t get charged. Again, this is quite similar to having a faulty alternator, there is no quick fix except to get the voltage regulator fixed. 

Corroded/lose battery connection

Pop your trunk and inspect the battery terminals. Do you see any white, blue, or maybe green powdery substance around the terminals? If yes, they might be the reason behind the stopped vehicle, leave the engine running message you received. These are by-products of a chemical reaction taking place within the battery. These powdery substances are non-conductors; as they accumulate, they could interfere with the flow of electricity (conductivity) around the battery terminals. Thereby preventing the battery from getting as much charge as it needs. Luckily there is a quick fix. All you have to do is clean and (if necessary) tighten any loose terminal connection. 

Conclusion

The stop engine leave vehicle running is a common problem that plagues most modern cars. It is not surprising that this problem seems to pop up recently. If you take a moment to consider, you would agree that most new cars are heavily padded with electronic accessories, which of course, makes driving them much more fun. But at the same time, it means the car demands more power from the battery. So when next you see the stop vehicle leave engine running message, you know just what to do.