Fault Family System: Powertrain (P-Codes) 8 SAE Codes

Reductant System Performance

Diagnostic & Technical Explanation

P202D (Reductant Leakage) is a system-level monitor rather than a single-component fault: it fires when the aftertreatment model detects reductant consumption trending too low or too high, no measurable dosing flow at all, or a physical leak in the DEF supply lines. Because these monitors compare modeled versus actual NOx reduction, the underlying cause is usually a partially clogged dosing injector, a slipping or kinked supply line, or diluted/contaminated fluid rather than a single sensor failure.

These 8 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 8 times.

Codes in this family (8)

Code	Definition	Repair coverage
P202D	Reductant Leakage	4 ranked fixes
P204F	Reductant System Performance Bank 1	4 ranked fixes
P205F	Reductant System Performance Bank 2	4 ranked fixes
P20F4	Reductant Consumption Too Low	4 ranked fixes
P20F5	Reductant Consumption Too High	4 ranked fixes
P20FE	Reductant Metering Unit 1 Performance	4 ranked fixes
P218F	Reductant No Flow Detected	4 ranked fixes
P2EAD	Reductant Metering Unit 2 Performance	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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