OBD-II code · Powertrain (generic, extended)
P2042 Reductant Temperature Sensor A Circuit
A general electrical fault is reported on reductant (DEF) temperature sensor A — used to compensate dosing for fluid viscosity and to enable tank heating in winter.
Is it safe to drive with P2042?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySensor element failed
- PossibleHarness 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)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–2.5 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Temperature Sensor, Reductant Tank
Related codes
- P2ACCReductant Temperature Sensor B Circuit
- P203FReductant Level Too Low
- P2040Reductant Injection Air Pressure Sensor A Circuit High
- P2041Reductant Injection Air Pressure Sensor A Circuit Intermittent
- P2043Reductant Temperature Sensor A Circuit Range/Performance
- P2044Reductant Temperature Sensor A Circuit Low
- P2045Reductant Temperature Sensor A Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.