What it means
The ECM detects a generic fault on the reductant tank B temperature sensor circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The reductant tank B temperature sensor provides DEF tank temperature information used by the emissions control module. This code indicates a general fault in that sensor circuit, so the module cannot rely on the tank B temperature reading for emissions control.
Common causes
Most likely first.
- Sensor failed
- Wiring or connector fault
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
- Read freeze-frame data and live tank B temperature to see whether the reading is missing, implausible, or intermittent.
- Inspect the tank B sensor connector and harness for corrosion, loose or pushed-back pins, broken insulation, and damage near the tank.
- Reconnect the sensor and check whether the live temperature signal returns or changes when the connector is secured.
- Use the wiring diagram to check circuit continuity and the sensor's electrical connections for opens, shorts, or poor contact.
- Test the tank B sensor and circuit against the manufacturer's specification to identify whether the sensor or wiring is at fault.
Common fixes
- Reconnect or clean the tank B sensor connector and repair loose terminals.
- Repair damaged wiring or a poor circuit connection.
- Replace the reductant tank B temperature sensor if it fails testing.
- Clear the code and confirm the module receives a plausible tank temperature.
Can I keep driving?
The vehicle may drive normally at first, but DEF or NOx warnings and a no-start countdown can occur if the emissions system cannot use the tank temperature signal. Limit unnecessary driving and have the fault checked promptly if a countdown appears.
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.