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2023-2026 Subaru Legacy Start Stop Memory Module | Fused Inline Harness
Product function
Fits: 2023–2026 Subaru Legacy models. The fitment table shows a 100% fitment match for each year. In these years the Legacy is a midsize sedan. The table does not break out trims. A Subaru Legacy from these years with factory Auto Start Stop and a matching connector fits.
Confirm first: Check the year against the fitment rows and look for the Auto Start Stop button. Make sure the connector matches the pictures.
What it leaves alone: Your Auto Start Stop button keeps working. No change is made to engine output, transmission behavior or charging. The Subaru Legacy can still refuse an automatic stop when conditions are not right.
The job it does: Auto Start Stop normally resets to on at every key cycle. The module keeps your previous selection, so one press is enough.
When stop-start is blocked: These vehicles carry an AGM or enhanced flooded battery for the extra cycling. A low charge, a cold engine or high climate demand can block an automatic stop regardless of the module. Replace the battery with the same type when it wears out.
How it connects: The harness connects at the stop-start switch circuit and includes an inline fuse on its power lead. No software is changed.
Ordering terms: Ships free within the lower 48 states: 1–2 business days to dispatch, 3–4 more on the road. A 45-day return window applies once a return is approved, less a 20% restocking fee and return shipping. 3-year limited warranty. Not sure? Email support@automotivebypass.com with your VIN, Monday to Friday 9–5 PST.
Select your vehicle in the fitment guide to confirm this product is right for your year, make and model.
Description
Built for the 2023–2026 Subaru Legacy, this fused memory harness keeps Auto Start Stop in whatever state you left it. Press the button once, and the setting carries over to the next start. The harness connects at the stop-start switch circuit and includes an inline fuse on its power lead.
Nothing is reprogrammed in the engine computer. The module only stands in for the button press you would otherwise make after every start, and it comes out without leaving a trace.
Which Subaru Legacy models it fits
The fitment table for this SKU lists the following, each marked as a 100% fitment match:
- Subaru Legacy: 2023–2026
The table does not separate trims; what matters is that the vehicle has factory stop-start and the connector shown in the photos.
How factory stop-start works on the Subaru Legacy
Each start of the Subaru Legacy begins with Auto Start Stop enabled. The switch on the dash can disable it, but only until the key is cycled. This module records the switch position and repeats it after the restart, which is the entire job it does.
Installation and removal
The harness connects at the stop-start switch circuit and includes an inline fuse on its power lead. Disconnect nothing else and splice nothing. Once both plugs are locked, tuck the harness where it will not be pinched when the panel goes back on. Test by switching Auto Start Stop off, cycling the ignition and checking the indicator.
Typical reasons to keep it off
Stop-start saves the most fuel in long idles, but plenty of drivers would rather keep the engine running. Common reasons: towing or hauling, where an engine restart under load is unwelcome; drive-thru lines and parking lots, where the engine cycles on and off every few feet; hot days, when the A/C compressor stops with the engine on many vehicles; and stop-and-go traffic where the restart delay is noticeable when pulling into a gap. On a midsize sedan, any of these can mean a button press at the start of nearly every drive.
Diagnostics first
A warning light that appears after installation usually means a connector is not fully seated. Switch the ignition off, reseat both ends until the locks click, and test again. If the light stays on, remove the module and confirm the vehicle is fault-free on its own before contacting support.
A note on the battery
The module draws its power from the vehicle and does not change charging behavior. If your Subaru Legacy sits for long periods, the same rules apply as without it: a maintainer helps, and a battery that tests weak should be replaced with the type specified for stop-start vehicles (usually AGM or EFB).
Conditions the factory system checks
The factory system will skip an auto stop for many reasons: battery charge below its threshold, cold coolant, high climate-control load, a steep grade, the hood or driver door open, or a 4WD or tow mode on vehicles that have them. Those checks stay in control after this module is installed. It does not force stops and it does not bypass any of those safety inputs.
What the module does and does not do
- Holds the stop-start button state between drives.
- Leaves no permanent change after removal.
- Leaves engine and transmission software untouched.
- Lets you re-enable the system with the factory button at any time.
Confirm these points
- Model year and model match a row in the table above (2023–2026 Subaru Legacy).
- Your Subaru Legacy has the factory stop-start button. Base trims or engines without stop-start have nothing for the module to remember.
- The connector at your install point matches the one in the product photos.
- The battery and charging system test good and no warning lights are on.
- No aftermarket remote start, alarm or gateway bypass is wired into the same circuit. If one is, email support before ordering.
- If you are unsure, send your VIN to support@automotivebypass.com and we will confirm fitment.
Warranty and returns
Free standard shipping covers the contiguous US, with dispatch in 1–2 business days and 3–4 days on the road after that. You have 45 days to request a return (pre-approval required, 20% restocking fee, buyer-paid return shipping). The module is backed by a 3-year limited warranty. For order or fitment questions, write to support@automotivebypass.com between 9 and 5 Pacific, Monday through Friday.
Questions & Answers
Will it fix a "stop-start unavailable" message?
No. That message usually points to the battery or a sensor. Diagnose and repair that first.
Which Subaru Legacy years does this fit?
The listed range is 2023–2026. Check the fitment table on this page against your exact model year.
Does it change engine power or fuel trims?
No. It does not reprogram the engine or transmission computers. It only stores the stop-start button state.
Can I remove it later?
Yes. Unplug the module and reconnect the factory connector; the vehicle returns to its stock default.
Will Auto Start Stop come back on when I restart my Subaru Legacy?
Not if you turned it off before shutting down. The module repeats your last selection at the next start. If you leave it on, it stays on.
Why does Auto Start Stop turn itself back on every time?
Automakers set stop-start to default to on at each start. Under EPA test rules, a system that stays off after shutdown is tested both on and off and the results are averaged, which lowers the rated fuel economy, so most systems reset at every key cycle. The module carries your last choice across that reset.
Is this the same part for every Subaru?
No. Connectors and the module that holds the stop-start state differ by platform, so this SKU is matched to the fitment rows on this page. Send the VIN to support if you are unsure.
How does it connect?
The harness connects at the stop-start switch circuit and includes an inline fuse on its power lead.
Does it change how the battery is charged?
No. Charging is still managed by the vehicle. Stop-start vehicles normally use an AGM or EFB battery built for frequent restarts; replace it with the same type when it wears out.
Why does my Subaru Legacy sometimes not auto-stop even when the system is on?
The factory logic checks battery charge, engine temperature, climate load and other inputs. If any are outside range it keeps the engine running. The module does not affect those checks.
Does the stop-start button still work after installation on the Subaru Legacy?
Yes. The factory button works normally. The module simply stores whatever you chose last.
What happens if I unplug it?
The vehicle returns to the factory default, with Auto Start Stop switched on at every start.
Does my Subaru Legacy need the factory stop-start button for this to work?
Yes. The module works with the factory stop-start system and its button. A vehicle built without stop-start has no setting for it to remember.
Vehicle Fitment
Additional Information
- Brand
- Automotivebypass
- Fits vehicle make
- Subaru
- Product type
- Auto Start Stop Eliminator
- SKU
- RC-ASSE-37-05
- Brand
- Subaru
- Installation
- Confirm the connector location and installation steps for your exact vehicle before ordering.
- Package
- Review the product description and included contents before ordering.
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