Powertrain, generic (extended)

P24EA NH3 Sensor Supply Voltage Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The NH3 sensor is a smart unit: its electronics module needs its own power feed, usually switched battery voltage through a fuse or relay, to run the probe, the heater and the J1939 link. P24EA is the general fault of that supply, set when the measured feed voltage is missing, unstable or otherwise outside the valid window without being classed as clearly low or high. Navistar describes this type of module on the 2013 N13 as one that runs its own internal checks and reports them over the data link, which only works with clean power. No manufacturer publishes P24EA. CARB expects heavy-duty OBD to catch circuit faults on such components. P24EB and P24EC are the low and high cases.

Likely causes

Fuse or relay in the sensor feed faulty or loose
Damaged or corroded power or ground wire to the sensor module
Supply monitoring in the sensor module defective

Symptoms

  • Check engine light on
  • Further NH3 sensor or communication codes stored

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,200
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

nh3 sensorsupply wiring

Related codes

P24EBP24ECP24E1

References: law.cornell.edu, static.nhtsa.gov.