Fault Family System: Powertrain (P-Codes) 19 SAE Codes

Reductant Level Sensor

Diagnostic & Technical Explanation

P203A (Reductant Level Sensor A Circuit) is the resistive or capacitive float sensor that reports how much diesel exhaust fluid remains in the tank, across up to three redundant sending points (A, B, C). A float arm gummed up by urea crystallization, a cracked sender housing letting fluid wick into the connector, and a sender mechanically stuck at one reading are the dominant failure modes, and the code fires whether the signal is out of range, frozen, or simply absent.

These 19 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 19 times.

Codes in this family (19)

Code	Definition	Repair coverage
P203A	Reductant Level Sensor A Circuit	3 ranked fixes
P203B	Reductant Level Sensor A Circuit Range/Performance	3 ranked fixes
P203C	Reductant Level Sensor A Circuit Low	3 ranked fixes
P203D	Reductant Level Sensor A Circuit High	3 ranked fixes
P203E	Reductant Level Sensor A Circuit Intermittent/Erratic	3 ranked fixes
P203F	Reductant Level Too Low	3 ranked fixes
P21A8	Reductant Level Sensor B Circuit	3 ranked fixes
P21A9	Reductant Level Sensor B Circuit Range/Performance	3 ranked fixes
P21AA	Reductant Level Sensor B Circuit Low	3 ranked fixes
P21AB	Reductant Level Sensor B Circuit High	3 ranked fixes
P21AC	Reductant Level Sensor B Circuit Intermittent/Erratic	3 ranked fixes
P21AD	Reductant Level Sensor C Circuit	3 ranked fixes
P21AE	Reductant Level Sensor C Circuit Range/Performance	3 ranked fixes
P21AF	Reductant Level Sensor C Circuit Low	3 ranked fixes
P21B0	Reductant Level Sensor C Circuit High	3 ranked fixes
P21B1	Reductant Level Sensor C Circuit Intermittent/Erratic	3 ranked fixes
P21C5	Reductant Level Sensor A Stuck	3 ranked fixes
P21C6	Reductant Level Sensor B Stuck	3 ranked fixes
P2D5A	Reductant Level Sensor A/B Correlation	3 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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