Engine Auto Stop-Start Not Working Troubleshooting

Engine Start Stop Not Working

Are you wondering “Why the auto start-stop is not working? or “Why the ECO engine feature is not working sometimes or at all?” The engine auto start-stop feature may stop functioning due to a variety of reasons, including:

  • The engine is still warming up: When the auto start-stop feature is activated, the engine may take some time to warm up to the optimal operating temperature. If the engine is still warming up, the auto start-stop feature may not function properly.
  • The outside temperature is too low or too high: The auto start-stop feature may also be affected by extreme high and low temperatures. If the temperature outside is too cold or too hot, the auto start-stop feature may not work as intended.
  • The battery charge is low: The auto start-stop feature relies on the vehicle’s battery to function properly. If the battery charge is low, the auto start-stop feature may not work as it should.
  • The battery temperature is outside the optimal operating range: The auto start-stop feature may also be affected by the temperature of the battery itself. If the battery temperature is too high or too low, the auto start-stop feature may not function properly.
BMW Comfort Access Keyless Entry Start Problems

Repeated frequent stops can also deactivate the stop-start system. Some manufacturers require the car to travel a certain distance or reach a certain speed before the system can be reactivated. In diesel cars, the stop-start system may not work if the car is going through a self-cleaning process for the diesel particulate filter. Lastly, the state of charge for the battery may also affect the stop-start system, as the system may not work if the charge is below 80% to prevent the risk of the car not being able to start again.

Why doesn’t the engine auto start/stop work when the car stops?

start stop 01
What prevents auto start stop from working.

The engine start/stop function is designed not to shut off the engine unless certain conditions are met or if there is an underlying problem. The system does not stop the engine if:

  • The battery is too weak or discharged.
  • The engine has not reached the operating temperature
  • The driver’s door is open.
  • The driver’s seatbelt is not bucked.
  • The vehicle is at a high altitude.
  • The heated windshield or heated seats are on.
  • Hood is open
  • The transmission is in manual (M) mode.
  • Transmission is in limp or emergency mode.
  • The vehicle is stopped on a steep grade.
  • The engine is still warming up.
  • The outside temperature is extremely low or too high.
  • Battery temperature is outside the ideal range.
  • Car may not have the echo start/stop feature installed at the factory.
  • A/C needs to maintain the interior climate temperature.
  • The driver turns off the start/stop feature.
  • Start/stop has been programmed to stay off by a mechanic.

Why does the engine restart automatically when stopped?

36368600 close up of a screwdriver held by a skilled mechanic
Close-up of a mechanic before repairing the engine start-stop and scanning the errors with diagnostic software in a modern automobile repair shop

The car automatically restarts the engine if:

  • A car battery is getting discharged too quickly.
  • The driver switches the heated windshield on.
  • Defrost is on.
  • The driver removes the seat belt.
  • The vehicle starts to roll in neutral.
  • The engine is required to run to maintain brake system assistance.
  • The engine is required to run to maintain the interior cabin temperature.

Most Common Reasons Why Start/Stop Doesn’t Work

1. Battery Too Weak

Battery Replacement Mazda 3 2013-2018

So even though you can start up fine and there are no issues when you turn the key, the state of charge might be below 80%. If it’s below 80%, the engine control unit (ECU) won’t allow it to do the stop-start function. It does this because if it’s below 80%, there is a possibility that if the engine stops, it might not start back up again, and because there’s that possibility, it won’t take the risk, and it’ll disable the start/stop feature.

Nine out of ten complaints referring to the stop-start system have to do with the battery being below that 80% charge. The problem is that many people think their battery is fine because it starts the engine. That is not true, and if the battery state of health falls below that 80% threshold, the stop-start won’t work.

2. Repeated Stops


Our next reason that won’t allow your stop-start to work properly is repeated stops. If the start/stop function turns off the engine once and you move again, you must travel a certain distance and drive over a certain speed to reactivate that function and use the stop-start again.

This can vary from manufacturer to manufacturer. So again, refer to your owner’s manual, and you’ll be able to see specifically what you need to do to get the start/stop working again.

3. A/C Keeps Engine Running

AC A/C Climate Control Buttons Dashboard

If you expect the car to stop and keep a certain temperature, the air compressor must be running, which is a lot of draining on the battery plus requires the engine to run. The car knows this, so it keeps the engine running.

If it shuts down with the engine when the a/c or blower fan is going, it might not be able to start back up again. So because there’s a potential that that might happen, it disables the start/stop temporarily as a safety feature.

4. Engine Hasn’t Reached the Operating Temperature

Volkswagen Temperature Light Flashin

The engine temperature is the second biggest thing that will deactivate your stop-start system. The engine coolant temperature needs to be above a certain threshold before allowing the start/stop system to work properly. The biggest amount of wear that can happen to your engine is on a cold start.

So when you start up first thing in the morning, the car has to get to the right temperature and has enough oil circulating throughout the engine to lubricate all those moving parts. If it didn’t do that and just started and on, off and on, off and on from cold, it would prematurely wear the engine and cause problems later on. To prevent premature engine wear, the engine must warm up before the start/stop can work.

5. DPF Regen

catalytic converter of the vehicle

This next issue only affects diesel cars. All modern diesel cars, SUVs, and trucks have a DPF filter or a diesel particulate filter, which fills up with soot from the engine, and now and again, it needs to go through a self-cleaning process to get rid of that soot that’s in the exhaust. The ECU won’t interrupt DPF regeneration if it’s going through this procedure.

The car is designed to get through this procedure as quickly as possible; it won’t shut off the engine because it will have to restart the DPF regen again, which can take up to 30 minutes.

6. Fault Codes

hybrid battery charge level zero 0 dischared battery hardware monitoring

If fault codes are present in the engine control unit (ECU), the start/stop the feature may be disabled. Most vehicles are programmed to disable the start/stop functionality when the check engine light is on and a Diagnostic Trouble Code (DTC) is present. To find out why your stop/stop is not working or what fault codes are present, use the YOUCANIC scanner to run a full system scan on your vehicle.

7. Seat Belt Unbuckled

Seat Belt Buckle

Most cars are programmed not to shut off the engine if the driver is not wearing the seat belt. The engine automatically starts if the engine is turned off and the driver removes the seat belt. This is normal, and most cars are programmed to disable the start/stop function if the driver is not wearing the seat belt.

Troubleshooting Start Stop Not Working

YOUCANIC UCAN2 Scanner Quick Scan Control Units

There could be several reasons why your engine echo start/stop function is not working. To determine the cause of the problem, it will be necessary to diagnose the issue and perform any necessary repairs. Using the YOUCANIC scanner to look at your vehicle, run a Quick Scan, diagnose the issue, and uncover the needed repairs is a good idea.

  1. Connect the YOUCANIC scanner to the OBD-II port under the dash. All vehicles 1996 and newer have this port. Chevrolet OBD2 Port Location
  2. Turn on the scanner and select Diagnose. YOUCANIC UCAN2 Scanner Home Page
  3. Select your Make, Model, and Year or hit SmartVIN to detect the vehicle you are troubleshooting automatically. YOUCANIC UCAN2 Scanner Select Make
  4. Go to Control Unit and select Engine Control Unit, which typically is the first option. YOUCANIC UCAN2 Scanner List of Control Units Modules
  5. Select View Live Data. YOUCANIC UCAN2 Scanner Read Clear Codes Live Active Tests
  6. Go to Start/Stop Function and select it.

The engine starts/stop function may not work because conditions set by the manufacturer are not met or because of a problem with the start/stop function. Let’s look at how to use the YOUCANIC scanner to find out why the start-stop function is not working. First, start by looking in the owner’s manual to find out what conditions the engine needs to meet before start/stop starts to work. For example, most vehicle manufacturers program the start/stop to stay disabled until the car reaches the normal operating temperature or warms up. If you are unsure why the start-stop function is not working, you can use the YOUCANIC diagnostic scanner to check what prevents the engine from stopping when the vehicle stops.

Frequently Asked Questions

How do I get stop-start to work?

To get the stop-start function on your car to work, you must first ensure that the system is enabled and properly functioning. Here are some steps you can take to troubleshoot the issue:
Check the battery: Make sure that the battery is fully charged and functioning properly. A weak or dead battery can prevent the stop-start system from working.
Check the system settings: The stop-start function may be disabled or turned off. Consult your car’s owner’s manual or check the vehicle’s settings to see if the system is enabled.
Check for malfunctions: If the system is enabled and the battery is functioning properly, there may be a problem with one or more of the system’s components. It may be necessary to have a mechanic or someone with experience in car repair diagnose the issue and suggest the appropriate repairs.
Check the fuel system: If the stop-start system is not working and there are no obvious problems with the battery or system components, there may be an issue with the fuel system. This could include problems with the fuel filter or fuel pump.
It’s important to note that the stop-start function may not work in all driving conditions, such as when the engine is cold or when the vehicle is being driven at high speeds. Consult your car’s owner’s manual for more information about the specific conditions under which the stop-start function is designed to work.

Does the start-stop function have a fuse?

Most cars do not have a dedicated fuse in the engine compartments to control the Start/Stop function. The Engine Control Unit typically controls the Start/Stop function (ECU). Use the YOUCANIC scanner to run a Quick Scan to determine why the start/stop isn’t working.

Does battery affect start-stop?

Yes, the battery can affect the operation of the start-stop function in a car. The start-stop system works by shutting off the engine when the vehicle is stopped, such as at a red light or in traffic, and then starting it again when the driver is ready to resume driving. This helps to save fuel and reduce emissions.
For the start-stop system to work properly, the battery must have enough power to start the engine when it is turned off. If the battery is weak or dead, the system may not be able to start the engine, and the start-stop function will not work. A weak or dead battery can cause other problems with the car’s electrical systems.
It’s a good idea to regularly check the battery to ensure it is in good condition. If the battery is low on power or is not functioning properly, it may need to be replaced. A mechanic or someone with experience in car repair can help diagnose any issues with the battery and suggest the appropriate repairs.

How long do stop-start batteries last?

On average, batteries on cars with start/stop function last about 4-5 years

What happens if you put a normal battery in a stop/start car?

Nothing. The replacement battery may only last two to three years instead of four to six, which is most common for cars with start/stop functions.

Do start-stop cars need special batteries?

Most vehicles with start/stop feature use AGM batteries. AGM battery is a maintenance-free battery that provides good electrical reliability and is lighter than the flooded lead-acid type. It stands up to low temperatures and has a low self-discharge. It can take a charge that is up to five times faster than the flooded batteries and has the ability to deep cycle.

Does start/stop wear out the starter?

The start-stop function on a car, which shuts off the engine when the vehicle is stopped and then restarts it when the driver is ready to resume driving, can potentially increase wear on the starter motor. This is because the starter motor is responsible for starting the engine and is subjected to additional wear and tear when used more frequently.
However, it is important to note that modern starter motors are designed to be able to handle the additional wear and tear associated with the start-stop function. In addition, the start-stop system is typically designed to minimize wear on the starter motor by only engaging it when necessary. For example, the system may use sensors to determine when the engine can be turned off and when it needs to be restarted. It may also use a “soft start” feature that gradually increases the starter motor’s power output to reduce wear.

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