The alternator itself doesn’t have any special sensors that will throw special codes in the ECU and hence the check engine light. But the failing alternator means that the voltage in the car’s electrical system will change – it will be much higher or much lower than it should be.
It means that a lot of systems will be affected like the charging system, the ECU, some sensors, and other electronic blocks and units. So, yes, the failing alternator can trigger the check engine light and some codes in the ECU.
What systems will the broken alternator affect?
Obviously, the alternator itself can’t throw a code and light up the check engine light. This is because the alternator is not equipped with the kind of sensor that would send the information directly to the ECU to let it know that there is some problem. But it doesn’t mean that when your alternator is broken, you will not see any error codes and the check engine light on your dashboard.
In most cases, the broken alternator will affect almost all units and blocks of your car and eventually, this will throw some codes.
Here are just some units that may malfunction because of the broken alternator or voltage regulator:
- The charging system
- The ECU
- The engine sensors
- The electronic fuel pump
- The injectors
- The transmission control unit
- The safety system
- The immobilizer
- The anti-theft system
This is not the entire list of systems and units that will malfunction once they get improper voltage. These are just examples of what may go wrong once the alternator is broken.
Also, you should know that if the alternator is completely dead, the 12-volt battery will take over the energy supply and you may not see the check engine light or some error messages appearing on the dash.
But the battery will be exhausted quite fast if it doesn’t get any charge, so after some time, the codes will appear anyway. The only system that may send a code in this situation is the charging system.
What codes can be triggered by a faulty alternator?
The malfunctioning alternator can throw almost any code because it will affect almost all units in your car. The actual codes will depend on what kind of damage we are talking about. If this is just too low or too high voltage, you may get any kinds of codes that will define problems with the safety system, the airbags, or the anti-theft system, etc.
But if the alternator is dead, you may expect your battery to kick in and supply all these modules with electricity. At least, for some time. So, you will not see the codes that would tell you about airbag problems or some other weird issues.
Most likely, you may see the following codes if you use a scanner at this moment:
- P0562 – this code tells you about the sharp drop in the voltage supply. So, it means that some units of your car including the charging system just don’t get enough electricity to work properly.
- P2503 – This code usually means that the battery is not charging or is charging very slowly. In most cases, the problem behind this code is that the alternator just doesn’t send enough electricity to your battery to let it charge.
- P0613 – This code usually appears when the transmission control module has problems. These problems can be caused by many issues but one of them is the wrong voltage that this unit gets.
- P0600 – This code may say about the problem with the ECU and again one of the possible reasons for this problem is that the ECU doesn’t get the proper voltage.
- Random codes – the faulty alternator can throw random codes that will falsely tell you about some problems in the system of your car while there is only one problem and this is the issue with the voltage.
I can continue telling you about all these codes but actually, it doesn’t make sense because the faulty alternator can trigger almost any code and it doesn’t tell you about the actual problem. If you get some weird error code with the help of your scanner, you should check first whether there is a problem with the battery or the alternator. Because sometimes these codes mean that the issue is connected to the electricity supply.
But the faulty alternator can not only throw codes but also show you some error messages without any codes behind them. Let’s look at this issue, too.
Random error messages with the faulty alternator
If your alternator is not working properly, it can’t supply the anti-theft system and also the safety systems with the proper electricity. Once this happens, your car ECU may make a conclusion that something is wrong with the safety of your vehicle.
This might trigger different error messages like “No Key Detected”, “Press Brake to Start”, “Engine Malfunction”, “Transmission Malfunction”, “ABS Failure”, “Airbag Deactivated” and many other messages that don’t make sense.
If this happens to you, the most important thing you should do is check whether your alternator and your 12-volt battery are working properly. You may notice that these random messages may change from time to time when you start your car.
Of course, if you see some error message, you shouldn’t immediately think that the only possible problem is the alternator or the battery. But remember this is one of the possible triggers of error messages.
How can you say that the alternator is malfunctioning?
Unfortunately, it’s quite hard to understand that your alternator is not really healthy. If it’s completely broken, your battery will be dead in just about a day or two. But if the alternator malfunctions but still works, you may be driving the car for a month or two months without understanding the problem.
Here are some signs that your alternator is not working properly:
- your accessories are working slowly or glitching;
- the car may stall just at the crossroad or at the light;
- the lights look very dim;
- there is a battery warning light on your dash;
- you hear the whining noise from under the hood.
Although these symptoms don’t always show you that the alternator is faulty, they may help you understand that there is a problem with charging your battery and supply all your electronic modules with electricity. If some of these signs are there in your car, you should check the alternator.
Common reasons for alternator problems
- Broken belt. The drive belt is a pretty important part of your car. It drives the alternator, the AC compressor, the steering wheel assist, and some other units and modules. If the drive belt is broken, none of these components will be working.
- Failed alternator. Although this part is pretty durable and it usually doesn’t require replacement or repairs, on high-mileage cars, it can still fail. In most cases, the problem is in the natural wear and tear.
- Voltage regulator problems. This is one more common situation for any modern car. The voltage regulator can fail and supply your electrical system in the car with the wrong voltage – too low or too high.
- Wiring problems. These issues can usually happen with cars that have been through some accidents. Damaged wires will not be able to supply your car with electricity from the alternator.
- Bad bearings. The alternator has a special axle inside that rotates on two bearings. If one or both of these bearings fail, the alternator may stop rotating. The drive belt will just slip and this will lead to all those problems that were mentioned above.
Again, these are not all the problems that can happen with your alternator, but just some of the most common ones.
Can you drive with a broken alternator?
Actually, you can drive with a broken alternator but your trip will not be very long. If the battery doesn’t get any charge, it’s likely to survive for about two or three hours. After that, the battery will be flat, and the car will die.
So, I don’t recommend continuing driving in this situation because eventually, you may end up being stuck on the roadside without the ability to drive your car. If this happens, it will be much harder for you to find some help. So, if this happened, better immediately think about where you can find technical help. You may drive for several miles but don’t rely on the battery. It may already be quite low and it may fail at any moment.