What it means
Voltage on the reductant tank B temperature sensor signal line is below the expected window. Wire shorted to ground or sensor short.
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
Reductant tank temperature sensor B reports the temperature of the corresponding tank area to the engine control module for emissions-system monitoring and control. P2ADB sets when the sensor B signal voltage falls below its expected range, commonly because the signal or supply is shorted to ground, the sensor is faulty, or its circuit has a poor connection.
Common causes
Most likely first.
- Signal wire shorted to ground
- Sensor fault
- Short to ground in the sensor supply 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
- Read freeze-frame data and related reductant faults, then check live temperature sensor B data for an unusually low or fixed reading.
- Inspect sensor B's connector and wiring at the reductant tank for chafing, corrosion, fluid intrusion, or a short to ground.
- Using the wiring diagram, check the sensor B signal and supply circuits for a short to ground and inspect the ground path for poor connections.
- Measure sensor B circuit behavior and compare it with the manufacturer's specification to distinguish a wiring fault from a sensor fault.
- If the wiring and connections pass, test reductant tank temperature sensor B and replace it if it pulls the signal below specification.
Common fixes
- Repair a sensor B signal or supply wire shorted to ground.
- Restore a poor or open sensor B circuit connection.
- Replace reductant tank temperature sensor B if it is internally shorted or out of specification.
- Clear the code and verify the temperature reading responds plausibly.
Can I keep driving?
The vehicle may remain driveable, but the low sensor B signal can disrupt reductant-system monitoring and trigger AdBlue/DEF or NOx warnings, possibly followed by a restart countdown. Arrange repair promptly and heed any countdown displayed.
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.