DEF Supply Module Heater Not Functional
What does DD-5742-7 mean?
The DD-5742-7 (Detroit Diesel DD Series) diesel fault code means: DEF Supply Module Heater Not Functional. This is a moderate severity code.
Common Symptoms
- Check Engine Light / Amber Warning Lamp illuminated
- DEF lamp in cold weather
Probable Causes (Ranked by Likelihood)
- Failed supply module heater Likely
Step-by-Step Diagnostic Procedure
Live-data heater command.
Replace DEF supply module if no heat.
Frequently Asked Questions
What is Detroit Diesel fault code DD-5742-7?
Detroit Diesel fault DD-5742-7 (SPN 5742 FMI 7) indicates: DEF Supply Module Heater Not Functional. 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-5742-7?
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-5742-7?
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.