What it means
The control module monitors the electrical circuit for reductant heater C. It sets this code when it detects an open circuit, meaning current cannot flow through the monitored path as expected.
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 another monitored portion of the DEF system so the fluid can be delivered in cold conditions. The control module monitors heater C’s electrical circuit and sets this code when it detects an open path that prevents the expected current flow.
Common causes
Most likely first.
- Heater winding open
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
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
- Record freeze-frame data and check for other heater codes to determine whether the fault is isolated to heater C.
- Identify the heater C assembly and connector from the vehicle’s service information, then look for corrosion, loose pins, or a terminal pushed back into the housing.
- Inspect heater C’s wiring for a break, chafing, or damage near the heated section and its mounting points.
- With the circuit isolated as directed by the manufacturer, test heater C’s winding for continuity against the manufacturer’s specification.
- If the heater and harness are intact, follow the manufacturer’s procedure to check for an internal open in the connected module or sensor assembly.
Common fixes
- Reseat or replace a pushed-back or damaged heater C connector terminal.
- Repair a broken or chafed section of heater C wiring.
- Replace the heater C element or assembly if its winding is confirmed open.
- Repair or replace a module or sensor assembly if testing confirms an internal open.
Can I keep driving?
In mild conditions the vehicle may remain driveable, but heater C’s portion of the DEF system may not warm properly in freezing weather. Watch for NOx warnings and any no-restart countdown, since continued operation can leave the SCR system unable to dose DEF and may eventually prevent restarting.
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.