DEF Dosing Reservoir Heater Not Operating
What does DD-4331-1 mean?
The DD-4331-1 (Detroit Diesel DD Series) diesel fault code means: DEF Dosing Reservoir Heater Not Operating. This is a moderate severity code.
Common Symptoms
- Check Engine Light / Amber Warning Lamp illuminated
- Cold-start DEF lamp
Probable Causes (Ranked by Likelihood)
- Failed tank heater Likely
- Coolant heater loop air-locked Possible
Step-by-Step Diagnostic Procedure
Check DEF tank temp rises after start.
Verify coolant flow through the DEF tank heat exchanger.
Replace tank heater or bleed coolant loop.
Frequently Asked Questions
What is Detroit Diesel fault code DD-4331-1?
Detroit Diesel fault DD-4331-1 (SPN 4331 FMI 1) indicates: DEF Dosing Reservoir Heater Not Operating. It is a moderate-severity fault and is commonly seen on DD13/DD15/DD16 engines in Freightliner and Western Star chassis.
Can I drive my Freightliner or Western Star with fault DD-4331-1?
It depends on severity. Critical and serious faults trigger derate or engine shutdown — do not continue driving. Moderate faults usually allow continued operation short-term but schedule repair to prevent cascading aftertreatment damage.
How much does it cost to fix Detroit Diesel fault DD-4331-1?
Typical repair cost is $500-$2,200. Sensor/harness fixes fall at the low end; turbo actuator, injector, aftertreatment component, or head gasket repairs fall at the high end. Detroit DDDL software and sometimes factory parameter reset are required for proper reset.