These instructions apply to the DS 9 Mk1 (X) 2021-Present.
For other models, please choose your vehicle here.
The automatic stop/start on your DS 9 (2021–present) cuts the engine at junctions to save fuel. On the E-Tense hybrid the changeover is smooth, but you can still switch the system off when you’d rather keep the engine running — with a single button. It’s a normal economy feature, not a fault, and the choice is handed back to you at the start of every drive.
How Stop/Start Works on the DS 9
The DS 9 is a plug-in hybrid, so it already shuts the petrol engine off whenever it can run on electric drive — the stop/start button here governs when the engine restarts at a halt. A battery-monitoring sensor watches the 12 V state of charge, and the car also weighs engine temperature, cabin climate demand and the hybrid system’s own needs. Because the electric side can hold the engine off or call it back on for its own reasons, the DS 9 sometimes keeps running even when you might not expect it. That behaviour is by design, not a fault.
Before You Begin
- You can press the button with the ignition on or the engine running — no special preparation is needed.
- To keep the engine on for a check, switch stop/start off first, then proceed.
- The setting isn’t stored: it returns to ON at the next start.
- On a hybrid, the engine may already be off under electric drive — that’s the hybrid system, separate from this button.
Turning Stop/Start Off
- Find the stop/start button — the ‘A’ / ECO OFF button, usually on the centre console or dash.
- Press the button once.
- The warning light illuminates to confirm the system is off — the engine now idles normally at a stop.
Turning It Back On
Press the button again, or restart the car — stop/start defaults to ON every time you start, so press the button each drive if you want it off.
Why It Sometimes Keeps the Engine Running
Even with stop/start active, the DS 9 holds the engine on when conditions aren’t met, for example:
- The 12 V battery charge is low, or the battery sensor isn’t satisfied.
- The cabin is still heating or cooling to the set temperature.
- The engine is still cold, or the hybrid system needs to run the engine.
- The drive battery is being managed or the car needs to warm the hybrid system.
- The car hasn’t fully stopped, or the brake isn’t firmly pressed.
If Stop/Start Won’t Work or Won’t Stay Set
- A weak or ageing 12 V battery is the most common cause — the system disables itself to protect it.
- After a battery change, fit the correct type and let it learn over a few drives before expecting normal cut-outs.
- A recent battery disconnect can suspend the feature until the car has relearned the state of charge.
- On a hybrid, engine behaviour also depends on drive-battery charge and temperature, so the engine may run more in cold weather.
- Strong heating, air-con or demister demand keeps the engine running to hold cabin comfort.
- A stored fault can disable it — look up the code on autodtcs.com.
After the Reset
Once you press the button, the warning light stays on for the rest of that drive and the petrol engine idles normally at every stop rather than cutting out. When you switch off and start again, stop/start returns to its default ON state, so you press the button once more if you want it off. On the E-Tense, the hybrid system continues to manage electric drive independently — the engine will still switch off when the car is running on battery power alone.
Frequently Asked Questions
How do I turn off stop/start on a DS 9?
Press the ‘A’ / ECO OFF button on the centre console or dash. The warning light comes on to confirm the system is off, and the engine then idles normally instead of cutting out at junctions. Press the same button again whenever you want the fuel-saving function back on for the rest of that drive.
Can I disable it permanently?
Not from the button alone — the DS 9 resets stop/start to ON every time you start, so the ‘off’ choice doesn’t carry over. The simplest routine is to press the button once each time you set off if you prefer the engine to keep idling while stationary.
Why does the engine keep running with stop/start on?
Because it’s a hybrid, the DS 9 runs the engine whenever the electric side needs it — to warm up, to manage the drive battery, or when cabin climate demand is high. A low 12 V battery, a cold engine, or the brake not being firmly pressed will also keep it idling. All of this is normal, not a fault.
Why won’t stop/start work at all?
The most common reason is a weak or ageing 12 V battery, which the car protects by disabling the feature. A recent battery disconnect, cold weather, or a lot of short trips can all leave the charge too low. Once the battery recovers, or is renewed with the correct type, stop/start usually returns on its own after a few drives.
Does the hybrid system affect stop/start?
Yes. On the E-Tense the petrol engine already switches off during electric running, and the hybrid controller decides when it needs to restart the engine — for warming up, charging, or extra power. So the engine’s stop and start pattern reflects both this button and the hybrid strategy working together, which can make it seem less predictable than on a petrol-only car.
Do I need a special 12 V battery for stop/start?
Yes — stop/start cars use an enhanced 12 V battery built for frequent cycling, separate from the high-voltage drive battery. Fitting an ordinary battery, or one of the wrong specification, can stop the system working. After any replacement, allow the car a few drives to relearn the state of charge before expecting normal engine cut-outs.
If a warning light came on with the fault, decode it on autodtcs.com.
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