Powertrain, generic (extended)

P24E3 NH3 Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P24E3 means the NH3 sensor signal lies below the lowest value an intact sensor can deliver. Usual culprits are a short to ground between probe and its electronics module, a terminal pushed back in the connector or a defect inside the probe. On International trucks with the 2013 N13 engine, a matching condition is reported as SPN 5848 with failure mode 4, i.e. the signal voltage of the mid-bed ammonia sensor too low or grounded. No manufacturer publishes P24E3 itself. CARB requires out-of-range checks for emission sensors on heavy-duty engines. While the fault is present the controller cannot trust ammonia feedback and has to dose from its model. P24E4 is the high counterpart, P24E2 the plausibility fault.

Likely causes

Chafed harness between probe and sensor module shorting to ground
Internal fault in the ammonia probe
Corroded or pushed-back terminal at the probe connector

Symptoms

  • Malfunction indicator lamp on
  • Scan tool shows ammonia reading stuck at minimum

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–1,400
Time0.5–2.5 h

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

Parts involved

nh3 sensor

Related codes

P24E1P24E2P24E4P24EB

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