By: Your van gulped a full 10-litre can of AdBlue last week, and the dash already wants more. At £15 a fill that stings—but the real worry is a looming no-start lock if the SCR ECU believes fluid is vanishing without lowering NOx.
RAC’s 2025 fleet study shows abnormal AdBlue use almost always traces back to five repeat offenders. The good news: four of the five can be diagnosed kerb-side with a cheap scanner and a flashlight. Follow the checks below before ordering pumps or injectors—you might solve the thirst in under 30 minutes.
💧 What counts as “too high”?
On Euro-6 vans the dosing rate sits near 3 % of diesel burn. A Sprinter running 30 mpg should sip roughly 1 L of AdBlue every 600 mi. Anything worse than a litre per 300 mi flags an over-dosing fault.
Live data item SCR_dose_qty should read 0.07–0.09 g/s at 2 000 rpm cruise;
numbers above 0.12 g/s mean the ECU is compensating for a leak, crystal blockage or false NOx reading.
🧰 Five common causes and quick checks
- Cracked return hose – look for wet streaks on the tank brace. The pump sees pressure drop and doubles dosing to maintain NOx target.
- Blocked injector tip – chalky crust narrows the nozzle, so the ECU stretches pulse-width and burns 50 % more fluid. Borescope the tip through the heat shield.
- Failing NOx sensor – if the downstream sensor drifts high, the ECU sprays extra urea. Live NOx > 200 ppm at idle hints heater drift.
- Over-concentrated fluid – DIY top-ups from open drums drive urea above 35 %. The ECU doses proportionally to concentration, so flow rises. A refractometer reading above 1.40 = drain and refill.
- Software corruption after jump-start – low voltage scrambles the SCR map, multiplying requested dosing. Flash the latest file via Autotuner to restore the correct table.
🔍 10-minute diagnostic routine
- Plug a scanner into the OBD port and note
SCR_dose_qty. - Key off, remove the blue return hose and feed it into a measuring jug; key on again. If more than 30 mL returns in 60 s at idle, the hose or injector leaks internally.
- With engine off, measure tank level. Drive a 20 mi urban loop; re-measure. A drop of more than 0.8 L signals true over-use.
- Read downstream NOx ppm at idle; over 300 ppm suggests sensor drift.
- If ppm looks normal yet dosing stays high, flash the latest SCR file; corruption resets pulse-width scalars to defaults.
🔧 Service options once you’ve found the cause
- Leaking hose or injector – replace £22 hose kit or £48 nozzle, then clear codes.
- Sensor drift – swap the downstream NOx sensor (£190–£320) and run the learning routine.
- Over-concentrated fluid – drain, rinse and refill using our spill-proof AdBlue top-up guide.
- Corrupted map – mobile flash takes 15 min and restores factory dosing.
- If none of the above solves it, book a deeper system flush through the mobile AdBlue service hub.
📈 Still burning AdBlue too fast?
Dial 07503 134 362 for a pressure test and live dosing check at your yard. We cover Stoke-on-Trent, Staffordshire, Crewe and surrounding areas — no workshop visit needed.
Read more on related pages:
Frequently asked questions
Will thick winter fluid raise consumption?
No. Dosing measures mass, not volume. Heaters warm the fluid to spec before injection.
Can I reset dosing with a pedal dance?
No pedal sequence resets SCR learned values—you’ll need a proper scanner or flash tool.
Does low-grade diesel change AdBlue use?
Higher-sulphur fuel increases DPF regens, not AdBlue dosing. It won’t affect urea flow rates.
