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.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Check engine light on
- No ammonia reading after warm-up
Most 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
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P24E6 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 4: Emissions
- E6: Specific fault in that system
Frequently asked questions
Can I keep driving with code P24E6?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P24E6?
The most common causes are: 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.
Related codes
- P24E7NH3 Sensor Heater Circuit Low
- P24E8NH3 Sensor Heater Circuit High
- P24E9NH3 Sensor Heater Circuit Performance
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.