P248DReductant Heater B Sense Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P248D means the heater B sense input reads too high, typically the heated line. Possible pictures are a sense wire shorted to battery positive, a supply that remains on after the heater has been switched off, or a faulty input stage. Public maker documentation for P248D does not exist. GM tests the line heater sense circuit only for undervoltage (P248C); Ford's 2023 diesels cover heater circuit 2, the pressure line heater, with P20C0 (switched off yet more than 5 V at the output) and the current codes P221C/P221D. CARB requires the reductant heating to be monitored. A line heater that never switches off wastes battery energy and can overheat the hose, so the relay is the first item to check.
- What you may notice
- Warning lamp
- Battery discharging while parked
- Likely causes
- PossibleLine heater relay sticking closed
- PossibleSense wire shorted to battery positive
- RareDefective input stage in the module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.