Bolt Remaps · Call 0203 038 8555

Symptom checker

What's wrong with my AdBlue?

A few quick questions. See the likely cause, how long you have, and what to do next.

Answer a few questions about your dash message, countdown, fault code and what happened just before. The checker shows the most likely causes, how urgent it is, and prefills a fixed-price quote.

The questions

What is your dash showing?

  • A countdown: “No start in 500 miles”, “Only 5 starts possible”
  • It won't start: Countdown hit zero or the engine is locked out
  • Warning light, no countdown: AdBlue or emissions light on, miles not shown
  • Low power / limp mode: Engine light and the vehicle feels restricted
  • I have a fault code: From a garage or your own scanner
  • Not sure: Something AdBlue related, can't tell what

How many miles are left?

  • Under 100 miles: Or under 5 starts
  • 100 to 500 miles: Days, not weeks
  • Over 500 miles: Some time, but it only goes one way

Which code is it?

  • P20EE: SCR efficiency below threshold
  • P20E8: Reductant pressure too low
  • P20E9: Reductant pressure too high
  • P207F: Reductant quality
  • P20BA: Reductant heater
  • P2200, P229F or U029D: NOx sensor codes
  • Something else: We'll read it on site

Have you topped up the AdBlue?

  • Yes, warning stayed on: Tank full, message still there
  • Yes, it cleared then came back: Went off for a while, now it's back
  • No, not yet: Haven't added any fluid
  • Not sure: Someone else drives it

Did anything happen just before?

  • Cold snap or frosty night: Came on in freezing weather
  • Right after a top up: New fluid, or filled from a different pump
  • After a recall or software update: Dealer visit, then the fault
  • After other work on the vehicle: Exhaust, DPF, clutch or wiring work
  • Nothing I noticed: It just appeared

Causes we check for

  • Crystallised or blocked dosing injector

    AdBlue dries into white crystals around the injector tip and stops it spraying properly.

  • Faulty NOx sensor

    The sensor that measures what comes out of the SCR catalyst reads wrong or drops out.

  • AdBlue pump or pressure fault

    The pump can't build or hold dosing pressure. Often inside the tank module.

  • Fluid quality or tank sensor

    Old, diluted or contaminated fluid, or a level/quality sensor that no longer reads the tank.

  • Tank or line heater failure

    AdBlue freezes at about -11°C. A dead heater leaves the system unable to thaw and dose.

  • Worn or contaminated SCR catalyst

    Less common. Only confirmed once dosing, fluid and sensors have been proven good.

  • Fault after a software update

    New calibrations can change fault thresholds or adaptations and trigger a fresh warning.

  • Wiring, connector or communication fault

    A damaged loom, corroded plug or lost signal to a sensor or module.

Checker questions

Can the symptom checker diagnose my vehicle?

No. It narrows down the most common causes for what you're seeing so you know how urgent it is. Only live data on the vehicle confirms the fault. That's what our diagnosis does, from £249 with a fixed price before work starts.

Why does topping up not clear the warning?

Once the SCR system logs a fault it wants proof the fault is gone, not just a full tank. If the warning stays after a top up, the cause is usually a pump, heater, quality sensor, injector or NOx sensor.

Is a countdown under 100 miles an emergency?

Yes. At zero the engine won't restart once switched off. Call us on 0203 038 8555 for a priority callout and avoid switching off anywhere you can't leave the vehicle.

Get a fixed price · AdBlue fault codes