OBD-II code · Powertrain (generic, extended)
P248B Reductant Heater A Sense Circuit High
Same as P248A with the sense voltage above the plausible range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Is it safe to drive with P248B?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySense line shorted to supply
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
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
- 1–3 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Heater A
Related codes
- P248DReductant Heater B Sense Circuit High
- P2488Exhaust Gas Temperature Sensor Circuit Range or Performance Bank 2 Sensor 5
- P2489Exhaust Gas Temperature Sensor Circuit Intermittent or Erratic Bank 2 Sensor 5
- P248AReductant Heater A Sense Circuit Low
- P248CReductant Heater B Sense Circuit Low
- P248EEGR Cooler Bypass Control Circuit Open Bank 2
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.