P204F — Reductant System Performance Bank 1

What P204F means

Reductant System Performance Bank 1. Common causes: DEF dosing system not meeting NOx reduction targets.

How serious is it?

Critical. Stop as soon as it's safe.

Most likely causes

1. DEF dosing system not meeting NOx reduction targets
2. Poor DEF quality
3. doser failure
4. SCR catalyst degraded

First moves (roadside)

1. Test DEF quality with refractometer
2. check doser flow
3. inspect SCR catalyst

FAQ

Related codes

Codes that commonly appear alongside P204F, or share the same subsystem.

• SCR Operator Inducement — Severe Derate Active (SPN 5246 FMI 0)
• Aftertreatment 1 Diesel Particulate Filter Differential Pressure - Data Valid But Above Normal Operating Range, Most Severe Level (DPF severely restricted / plugged) (SPN 3251 FMI 0)
• Aftertreatment 1 Diesel Exhaust Fluid Quality - Data Valid But Below Normal Operating Range, Most Severe Level (DEF quality/concentration incorrect) (SPN 4364 FMI 1)
• DPF Differential Pressure — Data Erratic (SPN 3251 FMI 2)
• DEF Dosing Unit — Not Responding Properly (SPN 3361 FMI 7)
• SCR Conversion Efficiency — Below Threshold (SPN 4364 FMI 18)
• DEF Quality — Out of Spec (SPN 4094 FMI 31)
• EGR Temperature — Too High (SPN 412 FMI 0)

Same symptom: DEF / SCR fault

Other codes in the DEF and SCR chain — the ones that end in an inducement countdown.

• Reductant Quality Deviation (P20EA) · Aftertreatment & Emissions
• DEF tank level low (SPN 1761 FMI 18) · Aftertreatment & Emissions
• DEF tank temp sensor — voltage high (SPN 3031 FMI 3) · Aftertreatment & Emissions
• Upstream NOx sensor — internal failure reported (SPN 3216 FMI 12) · Aftertreatment & Emissions
• SCR inlet NOx sensor — erratic (SPN 3216 FMI 2) · Aftertreatment & Emissions
• Upstream NOx sensor — abnormal update rate (SPN 3216 FMI 9) · Aftertreatment & Emissions

All Aftertreatment & Emissions codes

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