Auto Stop/Start and the auxiliary battery are two of the most misunderstood systems on the modern Jeep Wrangler and Gladiator platform. Introduced with the JL Wrangler in 2018—and carried over to the Gladiator at its launch in 2020—the aux battery wasn’t added to improve reliability, off-road performance, or electrical capacity. It exists for one primary reason: to support Auto Stop/Start as part of emissions and fuel-economy compliance. The two systems are related, but they are not the same problem, and confusing them has led to years of bad advice, unnecessary repairs, and electrical headaches. This guide breaks down what each system actually does, why it exists, and—most importantly—what needs to change depending on what you want your Jeep to do.
As of early 2026, Jeep has not officially announced plans to remove Auto Stop/Start or the aux battery from future Wrangler or Gladiator models. The feature exists today to help with emissions and fuel-economy compliance, and recent EPA proposals could reduce the regulatory incentive to include it, but no formal change from Stellantis has been confirmed.
2 Systems / 2 SOLUTIONS
- Auto Stop/Start (ESS)
- The Aux Battery
They interact, but they are not the same problem, and solving one does not automatically solve the other.
Let’s break this down cleanly.
First: Are Auto Stop/Start and the Aux Battery related?
Yes — but only functionally, not mechanically.
The Whole truth:
On late-model Jeep Wranglers and Gladiators, Auto Stop/Start and the auxiliary battery are inseparable in practice—even though they are not the same system. The aux battery exists primarily to support ESS, and when it begins to fail, it takes ESS down with it. What most owners aren’t told is that this isn’t a rare edge case. For many JL and JT owners, this moment arrives somewhere between 15,000 and 30,000 miles, often well before the main battery shows any signs of age.
When the aux battery starts to degrade, it can no longer hold voltage during engine-off events. The Jeep responds by disabling Auto Stop/Start, triggering warning messages, and—more critically—placing additional load on the main battery. Over time, this creates a cascading failure: a weak aux battery drains a perfectly good main battery, ESS becomes inconsistent or inoperative, and owners are left chasing electrical symptoms that feel unrelated but all trace back to the same root cause.
This is why so many late-model Jeep owners experience ESS errors, repeated battery replacements, or unexplained electrical quirks far earlier than expected. The system is doing exactly what it was designed to do—protect voltage stability for emissions compliance—but it was never engineered for long-term ownership, accessory loads, or the realities of overlanding and daily use beyond the factory warranty window.
Understanding this pattern is the key to making the right decision. Whether you choose to bypass ESS, replace the aux battery, or remove it entirely, the goal is the same: stop a small, premature failure from becoming a larger electrical problem.
Facts:
- The Aux Battery exists primarily to support Auto Stop/Start
- Auto Stop/Start relies on the Aux Battery
- You can disable ESS without deleting the Aux Battery
- You can delete the Aux Battery without fully disabling ESS (though it will usually stop working)
That’s where most of the confusion begins.
Are Jeep aux batteries known to be defective?
No official defect has been declared, and there has been no broad recall on the JL/JT aux battery system. Jeep (Stellantis) considers aux battery failures to be normal wear items.
However…
In real-world ownership, these aux batteries are widely known to fail prematurely. The aux battery isn’t defective — it’s undersized, overstressed, and optimized for compliance, not longevity.
That’s why:
- Dealers see it constantly
- Forums are full of confusion
- Overlanders and DIY’s delete it
- And ESS reliability collapses early for many owners
What the Aux Battery actually does
The Aux Battery:
- Momentarily powers vehicle electronics while the engine is off
- Prevents voltage drop during ESS events
- Protects sensitive systems when the main battery is heavily loaded
It is not there to:
- Start the engine
- Improve overall reliability
- Help off-road systems
- Unilaterally power accessories
In fact, it often becomes a failure point, especially in:
- High-mileage rigs
- Hot climates
- Vehicles with winches, fridges, compressors, or inverters
What Auto Stop/Start actually does
Auto Stop/Start:
- Shuts the engine off at a stop
- Restarts when brake pressure is released
- Exists for emissions and fuel economy compliance
- Cannot be permanently disabled from the factory
Key reality:
ESS will stop working automatically if battery conditions are not perfect — and Jeep considers that “normal operation.”
The Three Common Owner Goals
Most Jeep owners fall into one of these three camps:
- “I just want ESS turned off”
- “I want to eliminate the Aux Battery failure risk”
- “I want ESS gone and the Aux Battery gone”
Each has a different solution path.
Decision Flow Chart (Plain-English Version)
Auto Stop/Start (ESS) & Aux Battery Decision Table
| Step | Question | Answer | Recommendation / Outcome |
|---|---|---|---|
| 1 | Do you want Auto Stop/Start (ESS) to stop functioning? | Yes | Proceed to Step 1A |
| No | Leave ESS and Aux Battery stock | ||
| 1A | Do you want a reversible, non-invasive solution? | Yes | Use an ESS Bypass Module |
| No | Aux Battery Delete or Software Coding | ||
| 2 | Do you want to remove the Aux Battery due to reliability concerns? | Yes | Proceed to Step 2A |
| No | Keep Aux Battery and maintain it aggressively | ||
| 2A | Are you adding aftermarket electronics? (winch, fridge, inverter, lights, compressor) | Yes | Aux Battery Delete + Larger Main Battery |
| No | Aux Battery Delete + Proper Jumper / Bypass | ||
| 3 | Do you want both ESS disabled and the Aux Battery removed? | Yes | Aux Battery Delete (ESS will naturally stop working) |
| No | Choose only one modification above |
What Actually Happens in Each Scenario
Option 1: ESS Bypass Module (Most Conservative)
- ESS remembers your “off” button setting
- Aux Battery remains installed
- Zero warning lights
- Dealer-friendly
- Does NOT improve battery reliability
Best for: Daily drivers, lease vehicles, warranty-conscious owners
Option 2: Aux Battery Delete (Most Popular for Overlanders)
- Removes failure-prone Aux Battery
- ESS typically becomes inactive
- Reduces electrical complexity
- Requires correct wiring or jumper
- May trigger dash messages if done incorrectly
Best for: High-mileage rigs, off-grid travel, accessory-heavy builds
Best Way To Access: The passenger-side fender liner is the best, safest, and most repeatable way to access the aux battery. Turn wheels hard left or remove passenger front tire to access.
Accessing it from the top of the engine bay is possible, but it is harder, riskier, and usually not worth it.
Option 3: Full Delete + Electrical Simplification
- Aux Battery removed
- ESS disabled by design
- Main battery upsized (Group 94R / H7 common)
- Cleanest long-term solution
Best for: Long-term ownership, expedition builds, DIY-minded owners
The Biggest Myth (Worth Calling Out)
“If you delete the Aux Battery, you’ll damage the Jeep.”
False — if done correctly.
Problems arise when:
- The system is bypassed incorrectly
- Voltage sensing is ignored
- Battery capacity isn’t increased
- Cheap jumper cables are used
The Jeep doesn’t require the Aux Battery.
It requires stable voltage.
The Takeaway
Auto Stop/Start is a software behavior.
The Aux Battery is a hardware support system.
They interact — but they are not the same problem.
The Jeep doesn’t require the aux battery.
It requires stable voltage and proper circuit continuity.
If you respect that, both ESS bypasses and aux battery deletes can be done cleanly and reliably.
Tread lightly and Gladiator up! – Doug
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