Powertrain, generic (extended)

P24E6 NH3 Sensor Heater Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Like a NOx sensor, the ammonia sensor only measures once its ceramic element is hot, so it carries an electric heater. P24E6 reports that this heater circuit is open or otherwise electrically faulty: the driver commands heating but sees no current flowing. Common reasons are a burnt heater element, a broken wire in the pigtail or a terminal that lost contact. Without heat the probe stays cold and delivers no usable ammonia value, so dosing runs on the model alone. No manufacturer documents P24E6 publicly. CARB's heavy-duty rule requires a malfunction when heater current or voltage drop leaves the specified window. Low and high faults are P24E7 and P24E8; slow or unstable heating is P24E9.

Likely causes

Heater element inside the NH3 probe burnt through
Broken wire in the sensor pigtail near the hot exhaust
Heater terminal without contact in the connector

Symptoms

  • Check engine light on
  • No ammonia reading after warm-up

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€250–1,400
Time0.5–2 h

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

Parts involved

nh3 sensor heaterheater driversensor wiring

Related codes

P24E7P24E8P24E9

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