P248C code meaning
Reductant Heater B Sense Circuit Low
Powertrain system Generic code P24xx codes Check engine light
What P248C means
P248C reports too little voltage on the sense circuit of DEF heater B. In GM's diesel tables from 2016 to 2018 heater B is the line heater, i.e. the heated hose from the pump to the dosing valve. The test mirrors P248A: if system voltage exceeds the measured line heater supply by more than 3 V while heating is requested, 10 failures in 12 checks at 500 ms set the code, with cranking excluded and U010E as a blocking condition; no lamp type is listed. Ford's 2023 diesels likewise give the pressure line heater the letter B. A frozen hose that does not thaw causes dosing faults in winter, so a voltage drop at the line heater plug or in its fuse and relay path should be found early.
P248C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P248C
- DEF warning or engine lamp
- Dosing faults at low temperatures
Common causes of P248C
- Most likelyCorroded plug at the heated DEF line
- PossibleVoltage drop across fuse or relay of the line heater
- Less likelyDamaged supply lead along the frame
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant heater b
What each part of P248C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 8C | The exact fault in that area. |
What to do next
- Note P248C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P248C
What does P248C mean?
P248C means "Reductant Heater B Sense Circuit Low". P248C reports too little voltage on the sense circuit of DEF heater B. It is a generic code, so it means the same on every make.
Is it safe to drive with P248C?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P248C fail an emissions test?
Yes, it can. P248C is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P248C to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P248C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.