Cause
Faulty reductant pump
The pump that pressurises diesel exhaust fluid and delivers it to the dosing injector. Its enemy is the fluid it carries: urea solution crystallises wherever it dries, so a pump that stands unused — a car doing short runs, or one parked for months — can seize on its own deposits rather than wear out.
Symptoms arrive as dosing faults rather than pump faults: pressure that will not build, dosing that stops mid-cycle, and a NOx exceedence attributed to interrupted dosing. Many designs run a purge cycle at shutdown to pull fluid back out of the lines; a pump that cannot purge fails its neighbours too, so a seized pump often arrives with a blocked injector beside it.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (12)
Codes where this is a likely explanation first, rather than merely a possible one.
- P208B Reductant Pump A Control Performance/Stuck Off Likely for this code High
- P20E8 Reductant Pressure Too Low Likely for this code High
- P20FB Reductant Pump B Control Performance/Stuck Off Likely for this code High
- P2AD6 Reductant Pump Motor Position Sensor Circuit Likely for this code High
- P2AD7 Reductant Pump Motor Position Sensor Circuit Range/Performance Likely for this code High
- P2AD8 Reductant Pump Motor Position Sensor Circuit Low Likely for this code High
- P2AD9 Reductant Pump Motor Position Sensor Circuit High Likely for this code High
- P2BA8 NOx Exceedence - Interruption of Reagent Dosing Activity Likely for this code High
- P20F4 Reductant Consumption Too Low High
- P218F Reductant No Flow Detected High
- P2BAA NOx Exceedence - Low Reagent Consumption High
- P2BAF NOx System Driver Inducement Active High
Information, not instruction
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