What it means
Reductant Heater F Control Circuit: the control circuit has an electrical fault. The reductant (DEF/AdBlue) heater keeps the urea fluid from freezing; a fault can impair SCR dosing in cold conditions.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Reductant Heater F helps keep DEF/AdBlue from freezing so the SCR aftertreatment system can inject it when needed. P223B is set when the controller detects an electrical fault in the control circuit for Heater F, a distinct heater circuit from Heater E.
Common causes
Most likely first.
- Open or short in heater control wiring
- Faulty reductant heater element
- Loose or corroded connector
- Fault in the heater control circuit
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Review freeze-frame and aftertreatment live data for Reductant Heater F, noting its commanded state and any DEF or NOx warnings.
- Use the vehicle wiring information to locate Heater F and inspect its connector and harness for corrosion, broken wires, or heat damage.
- Check the Heater F circuit's fuses, power supply, grounds, and connector condition.
- Test the control wiring for an open or short and measure the heater element against the manufacturer's specification.
- If the heater and wiring pass, use the manufacturer's diagnostic sequence to check the control driver and related module connections.
Common fixes
- Secure or clean a loose or corroded Heater F connector.
- Repair an open, shorted, or damaged wire in the Heater F control circuit.
- Replace Heater F if its element fails the specified test.
- Repair a confirmed fault in the heater circuit's power, ground, or control connection.
Can I keep driving?
Driving may be possible, but cold conditions can prevent DEF from thawing and disrupt SCR dosing, raising emissions and possibly triggering a no-start countdown. Treat any countdown or DEF system warning as urgent and follow the vehicle’s stated limits.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.