P24B1 — Reductant Heater Control Circuit High
What it means: Reductant Heater Control Circuit High.
How serious / can you keep driving: Caution. Limp to the next safe stop.
Check first: Check DEF heater resistance
Don't risk it — look up listed providers near you and give them this code when you call.
Listed providers nearest Houston, TX
Closest first. Tell them P24B1 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Houston, TX · (832) 377-0578
- 0.0 mi away — based in Houston, TX · (713) 219-9090
- 0.0 mi away — based in Houston, TX · (713) 671-9751
Seen on: Heavy Truck/Diesel
What P24B1 means
Reductant Heater Control Circuit High. Common causes: DEF heater circuit open.
How serious is it?
Caution. Limp to the next safe stop.
Most likely causes
- DEF heater circuit open
- Broken wire
- failed heater
First moves (roadside)
- Check DEF heater resistance
- measure supply voltage
- replace heater element
FAQ
Reductant Heater Control Circuit High. Common causes: DEF heater circuit open.
Caution — Limp to the next safe stop.
The most common cause is: DEF heater circuit open. Other possibilities include Broken wire; failed heater.
Limp to the next safe stop. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside P24B1, or share the same subsystem.
- SCR Operator Inducement — Severe Derate Active (SPN 5246 FMI 0)
- Aftertreatment 1 Diesel Particulate Filter Differential Pressure - Data Valid But Above Normal Operating Range, Most Severe Level (DPF severely restricted / plugged) (SPN 3251 FMI 0)
- Aftertreatment 1 Diesel Exhaust Fluid Quality - Data Valid But Below Normal Operating Range, Most Severe Level (DEF quality/concentration incorrect) (SPN 4364 FMI 1)
- DPF Differential Pressure — Data Erratic (SPN 3251 FMI 2)
- DEF Dosing Unit — Not Responding Properly (SPN 3361 FMI 7)
- SCR Conversion Efficiency — Below Threshold (SPN 4364 FMI 18)
- DEF Quality — Out of Spec (SPN 4094 FMI 31)
- EGR Temperature — Too High (SPN 412 FMI 0)
Same symptom: DEF / SCR fault
Other codes in the DEF and SCR chain — the ones that end in an inducement countdown.
- Reductant System Performance Bank 1 (P204F) · Aftertreatment & Emissions
- Reductant Quality Deviation (P20EA) · Aftertreatment & Emissions
- DEF tank level low (SPN 1761 FMI 18) · Aftertreatment & Emissions
- DEF tank temp sensor — voltage high (SPN 3031 FMI 3) · Aftertreatment & Emissions
- Upstream NOx sensor — internal failure reported (SPN 3216 FMI 12) · Aftertreatment & Emissions
- SCR inlet NOx sensor — erratic (SPN 3216 FMI 2) · Aftertreatment & Emissions
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.