Cause
Reductant diluted or incorrect fluid
The SCR tank filled with something other than fresh diesel exhaust fluid — topped up with water, stretched with it, or filled with a fluid that never was DEF. The system measures the fluid's quality, not just its level, and dilute urea cannot convert the NOx the dosing calculation expects it to; the shortfall reads as an emissions exceedence with the tank apparently full.
The fix is honest fluid: drain and refill with DEF from a sealed container meeting ISO 22241. Concentration matters (32.5% urea is the spec, not a suggestion), the fluid ages in heat and sunlight, and a bargain top-up that triggers the inducement ladder is the most expensive saving a diesel can make.
Typically a moderate job.
Some of these codes mean you should stop driving
1 of the 11 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (11)
Codes where this is a likely explanation first, rather than merely a possible one.
- P207F Reductant Quality Performance Likely for this code High
- P20EE SCR NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 1 Likely for this code High
- P20F5 Reductant Consumption Too High Likely for this code High
- P241D SCR Inducement - Forced Engine Shutdown Likely for this code Stop driving Critical
- P249E Closed Loop Reductant Injection Control At Limit - Flow Too High Likely for this code Moderate
- P2BA9 NOx Exceedence - Insufficient Reagent Quality Likely for this code High
- U05A3 Invalid Data Received From Reductant Quality Module Likely for this code Moderate
- P208E Reductant Injection Valve Stuck Closed Bank 1 Unit 1 High
- P20F6 Reductant Injection Valve Stuck Open Bank 1 Unit 1 High
- P24FE SCR Catalyst Incorrect High
- P24FF Reductant Temperature Too High Moderate
Information, not instruction
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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.
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