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

Reductant Quality Sensor

Diagnostic & Technical Explanation

P206A (Reductant Quality Sensor Circuit) reports on the dedicated quality sensor that verifies the urea concentration of the diesel exhaust fluid in the tank, since fluid diluted with plain water or contaminated with the wrong concentration will not reduce NOx correctly. The sensor combines a temperature element and a dielectric/optical concentration element in one housing, and the code distinguishes a wiring/circuit fault at the sensor from a case where the sensor circuit is fine but the fluid itself reads outside the acceptable concentration band.

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
P206A	Reductant Quality Sensor Circuit	3 ranked fixes
P206B	Reductant Quality Sensor Circuit Range/Performance	3 ranked fixes
P206C	Reductant Quality Sensor Circuit Low	3 ranked fixes
P206D	Reductant Quality Sensor Circuit High	3 ranked fixes
P207F	Reductant Quality Performance	3 ranked fixes
P21CD	Reductant Quality Module Supply Voltage Low	3 ranked fixes
P21CE	Reductant Quality Module Performance	3 ranked fixes
P2B9A	Reductant Quality Sensor Circuit Intermittent/Erratic	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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