Fault Family System: Powertrain (P-Codes) 9 SAE Codes

NH3 Sensor Circuit

Diagnostic & Technical Explanation

Code P24E1 (NH3 Sensor Circuit) sets when the ECM sees an open, shorted, out-of-range, or intermittent signal from the ammonia-slip (NH3) sensor downstream of the SCR catalyst used to detect over-dosing of reductant, or finds the sensor's supply voltage out of range or its internal calibration memory has failed. NH3 sensors are sealed sensor-plus-module assemblies exposed to hot, corrosive exhaust gas, so element degradation, connector corrosion, and supply-circuit faults are the leading causes.

These 9 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 9 times.

Codes in this family (9)

Code	Definition	Repair coverage
P24E1	NH3 Sensor Circuit	3 ranked fixes
P24E2	NH3 Sensor Circuit Range/Performance	3 ranked fixes
P24E3	NH3 Sensor Circuit Low	3 ranked fixes
P24E4	NH3 Sensor Circuit High	3 ranked fixes
P24E5	NH3 Sensor Circuit Intermittent/Erratic	3 ranked fixes
P24EA	NH3 Sensor Supply Voltage Circuit	3 ranked fixes
P24EB	NH3 Sensor Supply Voltage Circuit Low	3 ranked fixes
P24EC	NH3 Sensor Supply Voltage Circuit High	3 ranked fixes
P24ED	NH3 Sensor Calibration Memory	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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