Symptom
Warning that the vehicle will not restart
A dashboard message counting down remaining starts or distance, usually on a diesel with selective catalytic reduction. This is not the car breaking — it is the car doing what it is legally required to do. Emissions regulations oblige these vehicles to enforce their own reductant system: first a warning, then a countdown, then reduced power or a hard speed limit, and finally no restart once switched off. The sequence runs while the car still drives perfectly, which is exactly why it gets postponed until the vehicle immobilises itself somewhere inconvenient. The countdown is displayed so the driver has fair warning; treat it as literal. Topping up the reductant clears it only when low fluid was the cause — where a fault is stored, the fault must be repaired.
Also described as: adblue warning, def warning, no restart warning, starts remaining, engine will not restart in, urea warning, countdown to no start, speed will be limited, emissions system warning, هشدار عدم روشن شدن مجدد, پیغام دیگر روشن نمیشود, aviso no volvera a arrancar, mensaje no podra arrancar, avisa que no arrancara otra vez, تحذير لن تشتغل مرة أخرى, رسالة عدم إمكانية التشغيل, تنبيه لن تعمل مرة ثانية
Some causes mean you should stop driving
7 of the 222 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.
What this usually means
This is not the car breaking. It is the car doing what emissions law requires it to do, and understanding that is what stops the countdown being postponed until the vehicle immobilises itself somewhere inconvenient.
The sequence is staged and German references give the usual distances. A first warning appears with roughly 2,400 km of range remaining; an urgent warning at around 1,000 km; a final stage near 500 km where the message becomes explicit — no engine start in X km. Then reduced power or a hard speed limit, and finally a refusal to start once the engine is switched off. The whole sequence runs while the car still drives perfectly, which is precisely why it gets ignored.
The countdown is not always about the fluid level, and this is the part that catches people out. A failed NOx sensor or a blocked dosing injector triggers exactly the same countdown with a full tank — so topping up clears it only when low fluid was the cause. Where a fault is stored, the fault has to be repaired, and refilling changes nothing except the owner's expectation. That is the commonest disappointed return in this whole area.
Crystallisation is the mechanical failure behind a large share of those faults. The fluid is a urea solution: when water evaporates or dosing is wrong, hard white deposits form and block the dosing module, the lines and the pump. Above about 50 °C the deposits become biuret, which is markedly more resistant than ordinary urea crystals — so a system left faulty gets harder to recover the longer it runs.
And the fluid itself is worth testing rather than trusting. A refractometer reads the urea concentration in seconds, and contaminated or wrong-strength fluid produces sensor faults that look like component failures.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Countdown displayed, reductant tank genuinely low | Normal consumption — the fluid is a consumable and the inhibit is a legal requirement | Check the level rather than assuming. The staged warnings begin around 2,400 km of remaining range, so there is ample notice if it is read. | Refill with correct-specification fluid before the countdown gets short. Never put anything else in the tank. |
| Refilled and the countdown continues | A stored fault rather than a level — a NOx sensor, a blocked dosing injector, or a pump fault triggers the same countdown | Read the codes. Common families are the NOx sensor's signal and heater circuits and low catalyst efficiency; a full tank with an active countdown is diagnostic on its own. | Repair the named fault. The countdown only resets once the system is satisfied, and refilling again will not do it. |
| Dosing faults with white crusty deposits at the injector or lines | Crystallisation — water evaporating or dosing running wrong leaves hard urea deposits that block the module | Inspect the dosing module and lines directly. Note that deposits formed above about 50 °C are biuret and far more resistant than ordinary crystals. | Clean or renew the dosing module and clear the lines. Address the dosing fault as well, or the deposits return. |
| Repeated system faults after refilling at an unfamiliar source | Fluid of the wrong concentration or contaminated — the sensors report a system fault rather than a fluid one | Draw a sample and test the urea concentration with a refractometer. This takes seconds and settles a question that otherwise costs a sensor. | Drain and refill with correct-specification fluid. Renew the sensor only if it remains faulty on good fluid. |
| Countdown appeared in very cold weather | The fluid has frozen or the tank heater has failed — the system cannot dose and reports it | Check the tank heater circuit and the ambient conditions when it began. The fluid freezes at a temperature ordinary winters reach. | Repair the tank heater. The frozen fluid itself is not damaged by freezing and is usable once thawed. |
| Car has already refused to start | The final stage of the legally mandated sequence, not a breakdown | Nothing to confirm mechanically. Establish whether a fault is stored as well as an empty tank, because that decides whether refilling will release it. | Refill and, where a fault is stored, repair it and reset with a scan tool. Some systems need a specific reset procedure even once satisfied. |
-
Countdown displayed, reductant tank genuinely low
- Likely cause
- Normal consumption — the fluid is a consumable and the inhibit is a legal requirement
- How to confirm it
- Check the level rather than assuming. The staged warnings begin around 2,400 km of remaining range, so there is ample notice if it is read.
- What fixes it
- Refill with correct-specification fluid before the countdown gets short. Never put anything else in the tank.
-
Refilled and the countdown continues
- Likely cause
- A stored fault rather than a level — a NOx sensor, a blocked dosing injector, or a pump fault triggers the same countdown
- How to confirm it
- Read the codes. Common families are the NOx sensor's signal and heater circuits and low catalyst efficiency; a full tank with an active countdown is diagnostic on its own.
- What fixes it
- Repair the named fault. The countdown only resets once the system is satisfied, and refilling again will not do it.
-
Dosing faults with white crusty deposits at the injector or lines
- Likely cause
- Crystallisation — water evaporating or dosing running wrong leaves hard urea deposits that block the module
- How to confirm it
- Inspect the dosing module and lines directly. Note that deposits formed above about 50 °C are biuret and far more resistant than ordinary crystals.
- What fixes it
- Clean or renew the dosing module and clear the lines. Address the dosing fault as well, or the deposits return.
-
Repeated system faults after refilling at an unfamiliar source
- Likely cause
- Fluid of the wrong concentration or contaminated — the sensors report a system fault rather than a fluid one
- How to confirm it
- Draw a sample and test the urea concentration with a refractometer. This takes seconds and settles a question that otherwise costs a sensor.
- What fixes it
- Drain and refill with correct-specification fluid. Renew the sensor only if it remains faulty on good fluid.
-
Countdown appeared in very cold weather
- Likely cause
- The fluid has frozen or the tank heater has failed — the system cannot dose and reports it
- How to confirm it
- Check the tank heater circuit and the ambient conditions when it began. The fluid freezes at a temperature ordinary winters reach.
- What fixes it
- Repair the tank heater. The frozen fluid itself is not damaged by freezing and is usable once thawed.
-
Car has already refused to start
- Likely cause
- The final stage of the legally mandated sequence, not a breakdown
- How to confirm it
- Nothing to confirm mechanically. Establish whether a fault is stored as well as an empty tank, because that decides whether refilling will release it.
- What fixes it
- Refill and, where a fault is stored, repair it and reset with a scan tool. Some systems need a specific reset procedure even once satisfied.
Codes that produce this symptom (222)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P0AA1 Hybrid/EV Battery Positive Contactor Circuit Stuck Closed Typical of this code High
- P0AA4 Hybrid/EV Battery Negative Contactor Circuit Stuck Closed Typical of this code High
- P0C78 Hybrid/EV Battery System Precharge Time Too Long Typical of this code High
- P0D32 DC/DC Converter A Over Temperature Typical of this code High
- P0D33 DC/DC Converter Current High Typical of this code High
- P0D42 Battery Charger 14 Volt Output Voltage Sensor Circuit Typical of this code High
- P0D43 Battery Charger 14 Volt Output Voltage Sensor Circuit Range/Performance Typical of this code High
- P0D44 Battery Charger 14 Volt Output Voltage Sensor Circuit Low Typical of this code High
- P0D45 Battery Charger 14 Volt Output Voltage Sensor Circuit High Typical of this code High
- P0D46 Battery Charger 14 Volt Output Voltage Sensor Circuit Intermittent/Erratic Typical of this code High
- P0D5B Battery Charger 14 Volt Output Power Performance Typical of this code High
- P0E31 DC/DC Converter Voltage Sensor A Circuit Typical of this code High
- P0E32 DC/DC Converter Voltage Sensor A Range/Performance Typical of this code High
- P0E33 DC/DC Converter Voltage Sensor A Low Typical of this code High
- P0E34 DC/DC Converter Voltage Sensor A High Typical of this code High
- P0E35 DC/DC Converter Voltage Sensor A Intermittent/Erratic Typical of this code High
- P0E36 DC/DC Converter Voltage Sensor B Circuit Typical of this code High
- P0E37 DC/DC Converter Voltage Sensor B Range/Performance Typical of this code High
- P0E38 DC/DC Converter Voltage Sensor B Low Typical of this code High
- P0E39 DC/DC Converter Voltage Sensor B High Typical of this code High
- P0E3A DC/DC Converter Voltage Sensor B Intermittent/Erratic Typical of this code High
- P0E51 DC/DC Converter Current Sensor A Circuit Typical of this code High
- P0E52 DC/DC Converter Current Sensor A Circuit Range/Performance Typical of this code High
- P0E53 DC/DC Converter Current Sensor A Circuit Low Typical of this code High
- P0E54 DC/DC Converter Current Sensor A Circuit High Typical of this code High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Others with this symptom
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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