What it means
This code indicates a low voltage condition in reductant heater A's control circuit.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Reductant heater A is an electrically powered heater for the DEF tank or a heated reductant section. The control module monitors voltage in heater A’s control circuit and sets this code when the circuit voltage is lower than expected, which can result from a short to ground or excessive resistance at a connection.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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 or power-supply codes, since shared supply or ground faults can affect heater A.
- Inspect heater A’s wiring and connector for rubbed-through insulation, corrosion, loose terminals, or moisture.
- Check the heater A circuit for a short to ground, following the manufacturer’s wiring diagram and isolation procedure.
- Measure voltage drop across heater A’s power and ground connections while the circuit is commanded on, and compare with the manufacturer’s specification.
- Test the heater A element and relay, then trace the control side to the module if the wiring and connections pass.
Common fixes
- Repair insulation chafed through to ground in heater A’s harness.
- Clean or replace corroded terminals and restore a sound connector fit.
- Repair a poor heater A ground or power connection.
- Replace a failed heater A element or relay after confirming the circuit fault.
Can I keep driving?
You may be able to drive if the vehicle has no other symptoms, but heater A may not protect its DEF section from freezing. Avoid relying on the vehicle in cold conditions, and heed any no-restart countdown because an emissions-system warning can progress to a restart restriction.
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.