P05F8
Reductant Heater Control Module Performance
Generic OBD-II
Common symptoms
What you'll notice
- Check the reductant heater control module for any malfunctions or damages
- Inspect and clean the reductant heater inlet and outlet pipes
- Test the reductant heater relay and replace if necessary
- Verify the electrical connections and wiring of the reductant heater control module
- Clear the error code and see if they return
Common causes
Most likely first
- Faulty reductant heater control module
- Clogged or dirty reductant injector
- Incorrect reductant fluid level
- Malfunctioning temperature sensor
- Wiring or connection issues with the reductant heater system
How to diagnose & fix
Work through it in order
- Check engine light illuminates on the dashboard
- Loss of power or decreased acceleration
- Poor fuel efficiency
- Difficulties starting the vehicle
- Rough idle or stalling
Read & clear P05F8 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.