What it means
Reductant Heater C Current Too High: the control module has detected this fault condition. 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 C heats DEF/AdBlue to support SCR dosing when the fluid is cold. This code sets when the control module detects more current through heater C than expected, often because the heater element or its wiring is shorted.
Common causes
Most likely first.
- Reductant heater element partially shorted
- Short in heater wiring
- Damaged or contaminated connector
- Faulty 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
- Check freeze-frame and live data to confirm whether reductant heater C was commanded on when the excessive-current fault appeared.
- Inspect heater C's connector for contamination, damaged terminals, or heat marks and check the harness for pinching or chafing.
- Check the heater C circuit for a short between wires or to a power source.
- With the circuit safely isolated as specified by the manufacturer, test heater C for an internally shorted element.
- If the heater and wiring pass, test the heater C control circuit according to the manufacturer's procedure.
Common fixes
- Repair heater C wiring that is shorted between conductors or to a power source.
- Clean or replace a contaminated or damaged heater C connector.
- Replace reductant heater C if its element is internally shorted.
- Repair the heater C control circuit if it fails the specified test.
Can I keep driving?
Avoid prolonged driving with this active fault, particularly in freezing weather, because excess current can damage the circuit and DEF heating may be impaired. Respond promptly to any DEF or NOx warning; some vehicles impose a no-start countdown when an emissions fault persists.
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.