P24EE says the microcontroller inside the NH3 sensor module has failed its own self-test, for example a watchdog reset, a RAM or ROM error or a timing fault. The engine controller only learns this through the status the sensor sends, because the processor is what runs the probe, the heater and the J1939 messages. Navistar explains for the 2013 N13 that its mid-bed ammonia sensor diagnoses itself and that probe and module are separate parts, ordered individually; a processor fault therefore normally means replacing the module. Repeated resets can also come from an unstable supply, so check that first. No manufacturer documents P24EE publicly. CARB requires fault detection on heavy-duty sensors. P24ED is the memory fault.
Medium severity. Can I keep driving?It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.
Symptoms
- Check engine light on
- NH3 sensor data missing or frozen
Most likely causes
- Electronics of the NH3 sensor module failed
- Unstable supply voltage causing processor resets
- Module damaged by heat or water ingress
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 P24EE means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 4: Emissions
- EE: Specific fault in that system
Frequently asked questions
Can I keep driving with code P24EE?
It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.
What causes code P24EE?
The most common causes are: electronics of the NH3 sensor module failed; unstable supply voltage causing processor resets; module damaged by heat or water ingress.
Related codes
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.