Common AdBlue Faults
AdBlue fault codes and warning messages.
These are some of the common P-codes linked to AdBlue, SCR, reductant pressure, reductant quality, tank heater, injector circuit and NOx sensor problems.
Common AdBlue and SCR P-codes
Some common fault codes related to AdBlue include P20EE, P205C and P20B9. P20EE can indicate an SCR/NOx catalyst efficiency problem, P205C points toward a reductant tank temperature sensor low-circuit issue, and P20B9 relates to the reductant heater control circuit. Other AdBlue codes can refer to pressure sensors, heater circuits, injector circuits, reductant quality, tank level and NOx sensor faults. These faults should be diagnosed with proper diagnostic equipment before parts are replaced.
P20E8
Reductant pressure too low: DEF pump failure, clogged DEF filter, low DEF level, blocked line or crystallised AdBlue.
P20E9
Reductant pressure too high: blocked DEF injector, faulty DEF pressure sensor, restricted dosing line or pump control fault.
P20EE
SCR NOx catalyst efficiency below threshold: SCR catalyst failure, poor quality DEF, NOx sensor fault or dosing fault.
P204F
Reductant system performance: DEF quality issues, injection system problems, SCR catalyst issues or system calibration faults.
P207F
Reductant quality performance: contaminated DEF, incorrect concentration, sensor issues or dosing system faults.
P203B
Reductant level sensor circuit range/performance: faulty DEF level sensor, wiring issues or low DEF level.
P203C
Reductant level sensor circuit low: DEF level sensor failure, wiring problems, connector fault or low DEF level.
P203D
Reductant level sensor circuit high: DEF level sensor issue, wiring fault, connector problem or tank module issue.
P2047
Reductant injection air pressure sensor circuit: faulty air pressure sensor, wiring issues or air supply problems.
P2048
Reductant injection air pressure sensor circuit low: sensor failure, wiring issues or air supply problems.
P2049
Reductant injection air pressure sensor circuit high: sensor failure, wiring issues or air supply problems.
P205B
Reductant tank temperature sensor circuit range/performance: faulty temperature sensor, wiring issue or sensor malfunction.
P205C
Reductant tank temperature sensor circuit low: temperature sensor issue, wiring fault or connector problem.
P205D
Reductant tank temperature sensor circuit high: sensor issue, wiring issue, connector fault or tank module problem.
P206A
Reductant quality sensor circuit: faulty DEF quality sensor, wiring issue or contaminated DEF.
P206B
Reductant quality sensor circuit range/performance: DEF quality sensor failure, wiring problem or connector fault.
P206C
Reductant quality sensor circuit low: DEF quality sensor issue, wiring problem or connector fault.
P206D
Reductant quality sensor circuit high: DEF quality sensor issue, wiring problem or connector fault.
P20B9
Reductant heater control circuit open: failed tank heater, pressure line heater fault, wiring issue or heater control fault.
P2200 / P2201 / P229F
NOx sensor circuit, range or performance faults. These can trigger AdBlue warnings, SCR faults, limp mode and countdown messages.
Manufacturer dashboard warnings
Audi
Common warnings include "AdBlue system malfunction", "Refill AdBlue" and make-specific P-codes for sensors, pump, heater or SCR faults.
Bentley
Common warnings include an AdBlue warning light, "Refill AdBlue" messages or AdBlue system malfunction warnings.
BMW
BMW warnings can include "Engine Start Not Permitted (AdBlue Empty)" and "AdBlue Fehlbefullung", meaning incorrect AdBlue filling.
Citroen
Citroen vehicles can show "Defective AdBlue Level Sensor" or "Refill AdBlue" warnings when tank level or sensor faults occur.
Ford
Ford warnings can include "AdBlue System Malfunction", "AdBlue Warning Light", "Refill AdBlue" or "Service AdBlue System".
Land Rover
Land Rover warnings include "AdBlue System Fault", "AdBlue System Malfunction", P242F AdBlue injection faults and related DPF/SCR messages.
Mercedes-Benz
Mercedes faults can include P13DF reductant metering unit faults and P13E0 to P13E6 faults for pressure line heaters, pump, injector and temperature sensor issues.
Volkswagen
VW warnings can include "AdBlue System Malfunction" and red AdBlue refill warnings where restart may not be possible without resolving the issue.
Common dashboard messages
- AdBlue system fault
- Engine will not start in 500 miles
- Top up AdBlue but the tank is already full
- Emissions fault or SCR fault
- Check anti-pollution system
- Limp mode after NOx or AdBlue fault
Do not replace parts from a code alone
One AdBlue fault code can have several causes. We check fault history, live data, dosing pressure, NOx readings, wiring, tank condition and software state before advising on repair or eligible off-road delete options.
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