What it means
DEF tank temperature sensor A signal jumps or drops out intermittently — connector or harness issue.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The reductant tank temperature sensor reports DEF/AdBlue temperature so the control module can manage tank heating and reductant availability. P205E sets when that signal jumps, drops out, or otherwise changes erratically, often because a connector or harness loses contact with vibration.
Common causes
Most likely first.
- Intermittent connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
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
- Save freeze-frame data and review live tank temperature data for sudden jumps or dropouts.
- Inspect the tank sensor connector and harness for loose terminals, corrosion, damaged insulation, or routing against a vibrating component.
- With the code active, gently move the harness and connector while watching live data for changes that reveal an intermittent contact.
- Check terminal fit and circuit continuity while moving the harness, following the manufacturer's procedure.
- If the wiring and connectors remain stable, test the sensor for intermittent output against the manufacturer's specification.
Common fixes
- Secure the harness away from vibration and rubbing points.
- Clean or repair connector terminals with intermittent contact.
- Repair damaged wiring or replace a faulty connector.
- Replace the tank temperature sensor if its signal remains erratic with a sound circuit.
Can I keep driving?
Driving may be possible if the vehicle behaves normally, but the fluctuating temperature signal can disrupt DEF/AdBlue heating decisions and emissions control. Monitor warnings closely and act on any start countdown, which may progress to a no-start 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.