P248A code meaning
Reductant Heater A Sense Circuit Low
Powertrain system Generic code P24xx codes Check engine light
What P248A means
P248A concerns the sense line with which the control unit measures the supply voltage reaching DEF heater A, and reports that voltage as too low. GM uses it on its diesels with an SCR power module for the tank heater: the 2016 to 2018 tables subtract the heater supply voltage from system voltage and fail a gap of more than 3 V while heating is commanded, after 10 of 12 checks at 500 ms; cranking is excluded and a lost connection to the reductant module (U010E) blocks the test. The tables leave the lamp column blank. Ford's 2023 diesels also assign heater A to the tank. A voltage drop of this size usually comes from a corroded plug, a weak relay contact or a damaged supply lead.
P248A 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 P248A
- Warning lamp or DEF system message
- Frozen DEF not thawed in winter, dosing delayed
Common causes of P248A
- Most likelyCorroded heater supply connector at the tank
- PossibleWorn heater relay contact causing voltage drop
- Less likelyWeak battery or charging fault during heating
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant heater a
What each part of P248A 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). |
| 8A | The exact fault in that area. |
What to do next
- Note P248A 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 P248A
What does P248A mean?
P248A means "Reductant Heater A Sense Circuit Low". P248A concerns the sense line with which the control unit measures the supply voltage reaching DEF heater A, and reports that voltage as too low. It is a generic code, so it means the same on every make.
Is it safe to drive with P248A?
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 P248A fail an emissions test?
Yes, it can. P248A 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 P248A to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P248A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.