Network, generic

U0298 Lost Communication With DC/DC Converter Control Module A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

A DC/DC converter adapts one direct voltage to another. Hybrids and EVs use it to charge the 12 V system from the traction battery, while some start-stop cars use it to keep the voltage steady for sensitive electronics during an engine restart. U0298 means converter module A no longer answers on the bus. Ford's 2014 OBD code list contains U0298 without the MIL. How this converter is supervised on start-stop vehicles is visible in its invalid-data partner: GM explains in 20-NA-191, covering CT4 and CT5 of model year 2020, that the ECM switches off auto stop at the first fault and lights the MIL at the second, and FCA lists DC/DC converter A data codes for the 2019 Cherokee V6. Expect start-stop to be withdrawn; on electrified cars the 12 V battery may run flat.

Likely causes

Converter connector corroded, often from water in the battery area
Blown fuse or missing supply at converter A
Bus wiring to converter A damaged
Converter A internally failed

Symptoms

  • Start-stop no longer active
  • 12 V battery discharging, charge warning
  • Electronics resetting during engine restarts

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–2,500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

dc dc converter module avehicle bus wiring

Related codes

U0299U0599U01BDP0A94

References: performanceparts.ford.com, static.nhtsa.gov, static.nhtsa.gov.