Fault Family System: Powertrain (P-Codes) 26 SAE Codes

Reductant Temperature Sensor

Diagnostic & Technical Explanation

P2042 (Reductant Temperature Sensor A Circuit) covers the thermistor-type temperature sensors placed in the reductant tank, supply line, or metering unit to manage freeze protection and dosing accuracy, since cold DEF must be thawed before accurate dosing can occur. The ECM differentiates a sensor reading outside its calibrated span, an open or shorted circuit, and an intermittent connection, all of which typically trace back to connector corrosion or a degraded thermistor element rather than the tank heater itself.

These 26 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 26 times.

Codes in this family (26)

Code	Definition	Repair coverage
P2042	Reductant Temperature Sensor A Circuit	3 ranked fixes
P2043	Reductant Temperature Sensor A Circuit Range/Performance	3 ranked fixes
P2044	Reductant Temperature Sensor A Circuit Low	3 ranked fixes
P2045	Reductant Temperature Sensor A Circuit High	3 ranked fixes
P2046	Reductant Temperature Sensor A Circuit Intermittent	3 ranked fixes
P205A	Reductant Tank Temperature Sensor A Circuit	3 ranked fixes
P205B	Reductant Tank Temperature Sensor A Circuit Range/Performance	3 ranked fixes
P205C	Reductant Tank Temperature Sensor A Circuit Low	3 ranked fixes
P205D	Reductant Tank Temperature Sensor A Circuit High	3 ranked fixes
P205E	Reductant Tank Temperature Sensor A Circuit Intermittent/Erratic	3 ranked fixes
P20AC	Reductant Metering Unit Temperature Sensor Circuit	3 ranked fixes
P20AD	Reductant Metering Unit Temperature Sensor Circuit Range/Performance	3 ranked fixes
P20AE	Reductant Metering Unit Temperature Sensor Circuit Low	3 ranked fixes
P20AF	Reductant Metering Unit Temperature Sensor Circuit High	3 ranked fixes
P20B0	Reductant Metering Unit Temperature Sensor Circuit Intermittent/Erratic	3 ranked fixes
P24F3	Reductant Tank Temperature/Fuel Temperature Correlation	3 ranked fixes
P2ACC	Reductant Temperature Sensor B Circuit	3 ranked fixes
P2ACD	Reductant Temperature Sensor B Circuit Range/Performance	3 ranked fixes
P2ACE	Reductant Temperature Sensor B Circuit Low	3 ranked fixes
P2ACF	Reductant Temperature Sensor B Circuit High	3 ranked fixes
P2AD0	Reductant Temperature Sensor B Circuit Intermittent	3 ranked fixes
P2ADA	Reductant Tank Temperature Sensor B Circuit Range/Performance	3 ranked fixes
P2ADB	Reductant Tank Temperature Sensor B Circuit Low	3 ranked fixes
P2ADC	Reductant Tank Temperature Sensor B Circuit High	3 ranked fixes
P2ADD	Reductant Tank Temperature Sensor B Circuit Intermittent/Erratic	3 ranked fixes
P2ADE	Reductant Tank Temperature Sensor B Circuit	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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