Engine Auto Stop-Start Not Working Troubleshooting

The start/stop system in modern vehicles is a fuel-saving feature that automatically turns off the engine when the car comes to a stop and restarts it when the driver presses the accelerator. However, if the start/stop system is not working properly, it can cause inconvenience and reduce fuel efficiency. After a battery change, the start/stop system may not work due to a weak battery, poor wiring connections, a bad start/stop control module, or other active systems. This issue is not limited to BMW vehicles but also affects Jeep, Jeep Compass, Jeep Grand Cherokee, Alfa Romeo, Audi A4, and other makes and models. If the start/stop system is not working, it is important to diagnose and repair the issue promptly to restore proper function and maximize fuel efficiency.

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Most Likely Reason why Echo Start/Stop Doesn’t Work

• 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 extremely 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 battery’s temperature. If the battery temperature is too high or too low, the auto start-stop feature may not function properly.

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 at a light?

The engine auto starts/stop system in vehicles may not work when the car stops for various reasons, such as a weak battery, a malfunctioning alternator, poor wiring connections, a false start/stop control module, or other systems being active (such as the air conditioning or audio system). If the battery is weak or not fully charged, the engine may not have enough power to turn off and restart automatically.

The alternator is responsible for maintaining the battery’s charge; if it is not working properly, the battery may not have enough power. Wiring issues between the battery, alternator, and start/stop control module can also prevent the system from functioning. If the start/stop control module malfunctions, the system may not work as intended. Other running systems may also prevent the start/stop system from functioning. It is recommended to have a qualified ASE mechanic diagnose and repair any issues with the start/stop system to ensure the car operates correctly and efficiently.

Start/Stop Requirements

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.

The engine starts automatically when stopped

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.

Troubleshooting

The start/stop system in vehicles allows the engine to turn off automatically when the car comes to a stop and turn back on when the driver presses the accelerator. If this system isn’t working properly, there are a few potential causes that a mechanic should check.

• Battery: The start/stop system requires a fully charged battery. If the battery is weak or dead, the system may not work.
• Alternator: The alternator is responsible for maintaining the battery’s charge. If the alternator is not working properly, the battery may not have enough power to run the start/stop system.
• Wiring: Wiring issues can prevent the start/stop system from working properly. A mechanic should check the wiring connections between the battery, alternator, and start/stop control module.
• Control Module: The start/stop control module controls the system. If the module malfunctions, the start/stop system may not work.
• Other Systems: If other systems, such as the air conditioning or audio system, are running, the start/stop system may not activate.

A qualified BMW mechanic should diagnose and repair any issues with the start/stop system to ensure that the car operates correctly and efficiently.

1. Battery Too Weak

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

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 might happen, it temporarily disables the start/stop as a safety feature.

4. Engine Hasn’t Reached the Operating Temperature

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

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

If fault codes are present in the engine control unit (ECU), the start/stop 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

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

There could be several reasons 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.

1. Connect the YOUCANIC scanner to the OBD-II port under the dash. All vehicles 1996 and newer have this port.
2. Turn on the scanner and select Diagnose.
3. Select your Make, Model, and Year or hit SmartVIN to detect the vehicle you are troubleshooting automatically.
4. Go to Control Unit and select Engine Control Unit, which typically is the first option.
5. Select View Live Data.
6. Go to the 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