What it means
Reductant Heater C Current Too Low: 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 warms DEF/AdBlue so the SCR system can dose it when temperatures are low. This code sets when the control module detects less current through heater C than expected, which may mean the heater is degraded or its circuit has excessive resistance.
Common causes
Most likely first.
- Reductant heater element partially open or degraded
- High resistance in wiring or connector
- Poor power or ground connection
- 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 heater data to confirm whether reductant heater C was commanded on when the low-current fault occurred.
- Inspect heater C's connector and harness for corrosion, loose pins, damaged insulation, or chafing.
- Check heater C power and ground connections for poor contact or excessive resistance.
- With the circuit isolated according to the manufacturer's procedure, test heater C for an open or degraded element against the manufacturer's specification.
- If the heater and connections pass, test the heater C control circuit using the manufacturer's procedure.
Common fixes
- Restore a poor power or ground connection at reductant heater C.
- Repair damaged or corroded heater C wiring and connector terminals.
- Replace reductant heater C if its element fails the specified test.
- Repair the heater C control circuit if it fails the specified test.
Can I keep driving?
The vehicle may remain drivable in mild conditions, but cold weather can prevent proper DEF thawing and SCR dosing. Do not ignore DEF or NOx warnings, as an unresolved emissions fault may lead to a no-start countdown on vehicles that use one.
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.