How Electronic Start Stop ESS Works on the Jeep Wrangler JL

The 3.6L Pentastar V6 in the new Wrangler JL utilizes the Electronic Start Stop System (ESS). The concept behind this is to save fuel by shutting the engine off automatically to prevent idling when the Jeep is sitting stopped. As usual when something changes many people will hate a change without fully understanding the benefits, the technology, or the big picture. Without creating a big political debate we wanted to explain some realities and how to live with this new system to save some money and contribute to the bigger picture.

How it Works

Once the Jeep’s engine is warmed up and the interior is within a range of set temperature the engine will enable ESS. If ESS is enabled when the Jeep comes to a complete stop and the brake is pushed the engine will automatically shut off, lights, HVAC, radio, and all accessories will remain on. As soon as the brake pedal is released the engine will near instantly start and you will be on your way. Start time is extremely quick and near silent. On an automatic moving a foot from the brake to the gas is enough time for the engine to start and get moving. Drivers new to ESS will experience a moment of panic the first few times the engine shuts off and one sits in near silence.

ESS active while stopped.

If the Jeep sits for an extended time the engine may restart to maintain battery or maintain heating/cooling levels.

ESS is automatically disabled in 4wd lo and on max AC.

ESS can be temporarily turned off by pressing the A switch on the dash. ESS will turn on the next time the Jeep is started.


Wear – Many think this system will cause wear to the starter and engine – Myth. ESS is not new technology and with this new technology comes systems designed to handle the increased starts and demands.

Reaction Time – The engine start time is near instant. Often the time it takes to move from the brake to the gas is enough for the engine to start and be on your way.

Annoyance – It’s a new concept for most and many obsess on the engine actually shutting off at a stop. Like anything else in life it takes getting used to. Turn the radio up and ignore it. 

Bigger Picture 


From a big corporate perspective FCA pays penalties for vehicles that get lower fuel mileage. Getting a vehicle to get 1-2 mpg improvement saves them big money and saves that cost from being passed on to us consumers – Jeeps are not cheap new or used. This is just a reality of big business.

Fuel Usage

The estimated fuel consumption of an idling engine is 0.16 gallons/hr per liter of engine displacement. This means that an idling 3.6 liter engine consumes more than a half gallon (.57 gallon) of gas per hour.

Letting your Jeep’s 3.6 engine idle to warm up once a day for 10 minutes for three winter months is 10 hours of idle time which equals 5.7 gallons (or around $15 at todays prices) of fuel that got you nowhere. A warm Jeep is nice though and may be worth $15.

Our experience: The JL is a daily driver and keeping a log of extended (30 seconds or more) stopped idle time over a two week period resulted in an average of 4.5 minutes per day (which is rather low). Over a 5 day work week this equals 22.5 minutes of idle time. Push that out over a year and that 1170 minutes or 19.5 hours of just idling. This is just over 11 gallons (or around $30 at todays prices) of fuel burned just sitting still. 

So 11 gallons seems trivial to some, take it further. Going off the last 5 years of the JK, Jeep produces well over 200,000 Wranglers per year and we could assume the JL will hit similar numbers. If we assume our stopped idle time is a low average just those 200,000 2018 JL Wranglers could collectively save 2.2 million gallons of fuel per year using ESS. With constant talk of cutting dependence on foreign oil this savings seems significant without even getting into what it means environmentally.

Living with it

With a little thought and an open mind a JL owner can quickly become used to driving their Jeep without getting annoyed and saving some money at the same time. Driving totally normally is possible but here are some tips to make the experience even better.

Brake Pedal Pressure – Light pressure on the brake pedal will prevent ESS from activating. Using just enough pressure to stay stopped will prevent ESS from activating. If you know you will be stopped momentarily use light pressure.

Stop and Go Traffic – We admit ESS is annoying in these situations and it may be best to turn it off or use light brake pressure.

Traffic lights ESS is nice at traffic lights. If arriving at a light that is about to change to green use light brake pressure. When at a light stay still, creeping will cause the engine to start and stop.

Stop Signs – Using light pedal pressure will prevent ESS from activating.

Fast Starts/Merging – If there is a need to accelerate from a stop quickly using light pressure or pressing the ESS off button might be best.

Hot Weather – On hot days that the AC may be running at high levels it might be best to turn off ESS since the demand for AC will cause the engine to start often. Running the AC on max will turn off ESS automatically.

Parking – Shift into park quickly and/or use light brake pressure when parking. Sitting too long before shifting into park will cause ESS to activate. Shifting into park will cause the engine to needlessly restart.

Defeating it

ESS can be temporarily turned off by pressing the A switch on the dash. ESS will turn on the next time the Jeep is started.

If for some reason you find yourself unable to deal with pressing a button, saving some money or helping the larger causes other Jeep owners have figured out ways to defeat the system on a semi-permanent basis.

Hood Switch – The JL has two hood switches that indicate to the computer that the hood is ajar or not. Evidently the 2nd switch on the driver most side is a backup switch to the first. Unplugging that switch will stop the ESS system from activating but not affect other systems such as remote start. A warning indicator will show on the dash while the switch is unplugged.

Hood Ajar Switches

Hood Ajar Backup Switch

Smart Battery Cable – The ESS has a small connector that plugs into the battery system to monitor voltage. If this connector is disconnected the ESS system will not activate.

ESS Battery Sensor

Computer Modification – Some vehicles have computer modifications available that can shut off ESS completely. Nothing like this exists for the JL yet. Time will tell if it will become available.

In the end it’s your decision as a Jeep owner if this system doesn’t fit into your world. There is no evidence that this causes wear to the Jeep. Saving a few bucks and saving some fuel seems attractive enough to make us leave the system operate as designed.

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