OBD-II code · Powertrain (generic, extended)
P24E8 NH3 Sensor Heater Circuit High
The heater control circuit of the NH3 slip sensor reads above the expected voltage range. Typically a short to battery voltage or a heater driver stuck high — duty-cycle control is lost, the heater either runs continuously or not at all, and the sensor element risks overheating before the ECM disables it.
Is it safe to drive with P24E8?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyHeater control wire shorted to battery voltage
- PossibleHigh-side driver stuck on
- Less likelyConnector pins corroded - high contact resistance
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.6–2 h
- Emissions test
- Likely to fail
- Parts involved
- Nh3 Sensor Heater, Heater Driver, Sensor Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.