What it means
Reductant temperature sensor A reads below its lower plausibility limit — short to ground. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Reductant temperature sensor A reports DEF temperature for dosing and tank-heating control. P2044 sets when its signal falls below the expected range, which can result from a short to ground or another circuit fault; it does not by itself prove that the sensor is reporting genuinely cold fluid.
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
- Check freeze-frame data and live sensor A temperature to confirm whether the reading is implausibly low while P2044 is active.
- Inspect the sensor A connector and harness for chafing, moisture, corrosion, pin push-back, or insulation worn through to ground.
- With the scan tool displaying the live reading, gently move the harness and connector to see whether the signal changes or the fault returns.
- Test the sensor signal wire and connector for a short to ground, using the manufacturer's wiring information and specification.
- If the wiring and terminals pass inspection, test reductant temperature sensor A against the manufacturer's specification.
Common fixes
- Repair wiring chafed through to ground and secure the harness away from sharp or moving parts.
- Clean or replace corroded terminals and correct any pushed-back connector pins.
- Replace reductant temperature sensor A if it produces a below-range signal despite a sound circuit.
Can I keep driving?
Avoid long trips if a DEF or NOx warning is active, and do not ignore any no-start countdown. The faulty reading can disrupt DEF heating or dosing, which may worsen emissions performance and prevent the vehicle from restarting after the countdown.
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.