01 From Farm Tracks To City Streets: Why The Land Rover Defend… • 02 Types of Chain Drives: Uses, Design, Application, Pros, and… • 03 Why Mechanics Don’t Always Show You the Real Fault • 04 What Happens Inside an Engine at High Speed • 05 Toyota Noah vs Nissan Serena: A Comprehensive Comparison • 06 100 Hilarious Things Mechanics Actually Say (That’ll Make Y… • 07 Inline vs V Engine: Pros, Cons, Power, and Fuel Efficiency • 08 How to Start a Rebuilt Engine for the First Time • 09 Infotainment Evolution: From AM and FM to Touchscreen Conne… • 10 What Happens If the Timing Chain of Your Car Breaks? •

DTC codes / U02xx · Lost communication with a control module / U0298

U0298Lost Communication With DC/DC Converter Control Module A

U0298 is a generic network communication code indicating that one or more control modules have lost the CAN (Controller Area Network) messages they expect from the DC/DC converter control module A. The DC/DC converter, which steps high-voltage down to charge the 12-volt system on hybrid and electric vehicles, is monitored by other modules, and when its periodic status messages stop arriving, the receiving module sets this code.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaLost communication with a control module

Symptoms you may notice

  • Illumination of the check engine light or a dedicated service vehicle warning lamp
  • Often no symptoms besides the warning light, with the vehicle driving normally
  • A 12-volt battery that repeatedly goes flat or accessories that behave erratically
  • Loss of high-voltage charging or a vehicle that refuses to enter ready mode
  • Multiple unrelated warning lights or communication codes stored in several modules
  • Reduced power or a limp-home mode if the converter is not maintaining the low-voltage supply

Common causes, most likely first

  1. A discharged, weak, or internally shorted 12-volt battery dragging down module supply voltage
  2. Corroded, loose, or damaged connectors and pins at the DC/DC converter control module
  3. Open or shorted CAN bus wiring between the converter module and the rest of the network
  4. A failed DC/DC converter control module that no longer transmits on the bus
  5. Poor grounds or power feeds shared by the converter module and its communicating partners
  6. A separate module on the same CAN segment holding the bus down and blocking communication
  7. Aftermarket accessories or improper wiring repairs that disturb the network

How to diagnose and fix it

  1. Perform a full scan of all modules and record every communication and voltage-related code before clearing anything
  2. Test the 12-volt battery state of charge and load capacity, and charge or replace it if it fails
  3. Inspect and clean the converter module connectors, checking for corrosion, pushed pins, and water intrusion
  4. Measure CAN bus resistance and voltage at the converter module connector to confirm the bus is intact
  5. Check the converter module's power and ground circuits under load with a multimeter or test light
  6. If the bus and supplies are good, substitute a known-good converter module or perform a bidirectional communication test
  7. Clear codes, verify the converter module responds on the scan tool, and road-test to confirm the code does not return

What a U0298 code often hides

  • A weak 12-volt battery is the most common cause of this code on hybrid and electric vehicles, because low supply voltage can silence the converter module before any component actually fails.
  • This code does not prove the DC/DC converter is bad; a different module shorting the CAN bus can block all traffic and make the converter appear offline.
  • Aftermarket alarms, dash cams, or phone chargers wired into the wrong circuit can back-feed the network and set communication codes like U0298.
  • Some vehicles set U0298 only after several drive cycles of missed messages, so a single occurrence after a battery disconnect may be a stored artifact rather than a live fault.
  • A converter module that communicates fine on the scan tool but sets U0298 intermittently usually points to a wiring harness chafe or a ground that loses contact over bumps.

Can I keep driving with U0298?

If the vehicle drives normally and only the warning light is on, a short trip to a shop is acceptable, but avoid long journeys because the 12-volt system may not be charging. If the battery is going flat, the vehicle will not start, or high-voltage warnings appear, stop driving and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage