P248A: Reductant Heater A Sense Circuit Low
Standardized SAE J2012 code · P24xx — Auxiliary emission controls
What does P248A mean?
Reductant Heater A Sense Circuit Low: the signal voltage is below the expected range. The reductant (DEF/AdBlue) heater keeps the urea fluid from freezing; a fault can impair SCR dosing in cold conditions.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
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)
Common causes
- High Sense line shorted to ground
- Low Connector pins corroded - high contact resistance
- Low Harness chafing through insulation
Likelihood is a general estimate across vehicles; your make and model may differ.
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