Code
U0299
Generic
U — Network/User
Lost Communication With DC/DC Converter Control Module B
Views:
UK: 15
EN: 36
RU: 21
AI status
Completed
Completed
100%
Causes
- Failed DC/DC converter control module B
- Loss of module power (blown fuse, open power feed)
- Poor or missing ground connection at the module
- Damaged, corroded, or disconnected connector/wiring
- CAN/LIN bus open, shorted, or high resistance
- Bus termination or wiring harness damage (pinched, chafed)
Symptoms
- MIL (check engine) or dash warning lamp illuminated
- Messages relating to 12 V system or charging may be present
- Low accessory/auxiliary battery voltage or charge faults
- Loss of features that rely on DC/DC converter B
- Multiple communication-related DTCs in other modules
- Intermittent or no communication with module via scan tool
What to check
- Read all modules with a capable scan tool; note freeze frame and related U-codes
- Verify whether the code is current, history, or pending; clear and see if it returns
- Visually inspect the DC/DC converter module connector for corrosion, damage, or water ingress
- Check fuses and relays supplying the module power and key/switched feeds
- Measure supply voltage and ground at the module connector with key ON
- Check CAN/LIN wiring continuity and for shorts to battery/ground using a digital meter
Signal parameters
- Module supply voltage: ~11–14 V with key ON/engine running (verify vehicle spec)
- Ground resistance at module: ideally
- CAN bus idle (recessive): both CAN_H and CAN_L near ~2.5 V (vehicle-dependent)
- CAN bus dominant differential: approx. 2 V difference (typical CAN_H ~3.5 V, CAN_L ~1.5 V)
- Termination resistance: approx. 60 ohms measured across CAN_H–CAN_L (two 120Ω in parallel)
- Expected activity: visible CAN frames on oscilloscope/scan tool when module is communicating
Diagnostic algorithm
- Connect a professional scan tool and read all U-codes and related faults; record freeze frame.
- Clear the code and attempt to communicate with DC/DC Converter Control Module B using the scan tool.
- If module is not found, inspect fuses/relays and verify the module has proper supply voltage with key ON.
- Check module ground(s) for good connection and low resistance to chassis.
- Visually inspect the module connector and harness for damage, corrosion, bent pins, or water intrusion; repair as needed.
- Measure CAN_H and CAN_L voltages at the module connector (key ON). Verify termination resistance across the bus.
- Use an oscilloscope or bus analyzer to check for valid CAN frames and to identify noise, stuck dominant bits, or collisions.
- If the physical layer is good and no communication is possible, check for other modules causing bus contention; disconnect suspected nodes if safe to do so and recheck communications.
- If wiring, power, and grounds are intact but the module is unresponsive, consult OEM service information for reprogramming or known module updates; consider replacement only after confirming module failure.
- After repair, clear DTCs, verify module presence on the network, and perform a road test to ensure the code does not return.
Likely causes
- Blown fuse or missing 12 V supply to DC/DC Converter Control Module B
- Disconnected, corroded, or bent pins at the module connector
- Open or shorted CAN (or LIN) wiring near the module
- Poor ground at module chassis or ground strap
- Module internal failure preventing bus response
- Network termination fault or another module driving the bus
Fault status
Status
Lost Communication With DC/DC Converter Control Module B — module not responding on the vehicle network.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Workshop Manuals
Available brands with manuals
2
AUDI 11
6-speed manual gearbox 0B1, front-wheel drive — Workshop Manual (Edition 05.2014)
Workshop Manual199,00 UAH
Audi A3 (1997) – 1.6L 4-cylinder (2‑valve) Engine Mechanical Components Service Manual (AEH, AKL, APF) – Edition 07.2002
Workshop Manual199,00 UAH
AUDI A3 (2004) Workshop Manual — 2.0L FSI Turbo (4‑cyl, 4‑valve) Engine, Mechanics — Edition 03.2017
Workshop Manual199,00 UAH
Audi A3 2004 — Electrical System (Workshop Manual, Edition 02.2018)
Workshop Manual199,00 UAH
Audi A4 / A4 Cabriolet – 4.2 l V8 (5‑valve, timing chains) – Workshop Manual (Mechanics) – Edition 04.2007
Workshop Manual199,00 UAH
Audi A4 / A4 Cabriolet — Auxiliary Heater Workshop Manual (Edition 08.2004)
Workshop Manual199,00 UAH
Audi A4 / A4 Cabriolet (1.8T 4‑cyl turbo) — Motronic Injection & Ignition System Service Manual (Edition 01.2015)
Workshop Manual199,00 UAH
Audi A8 (2003) — Electrical System Workshop Manual (Edition 08.2014)
Workshop Manual199,00 UAH
Audi Q4 e-tron (Type F4) - Self-study Programme SSP 685
Workshop Manual199,00 UAH
Audi Q8 (2018) — Electrical System Workshop Manual (Edition 05.2019)
Workshop Manual199,00 UAH
Audi Servicing Manual — 7‑Speed Dual Clutch Transmission 0CJ / 0CL / 0CK / 0DN / 0DP / 0HL (Edition 05.2018)
Workshop Manual199,00 UAH
LAND ROVER 3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop Manual199,00 UAH
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop Manual199,00 UAH
Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop Manual199,00 UAH
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email
Code
U0299
HYUNDAI
U — Network/User
Lost Communication With DC to DC Converter Control Module “B”
Views:
UK: 15
EN: 36
RU: 13
AI status
Completed
Completed
100%
Causes
- Failed DC/DC converter control module B
- Loss of module power (blown fuse, open power feed)
- Poor or missing ground connection at the module
- Damaged, corroded, or disconnected connector/wiring
- CAN/LIN bus open, shorted, or high resistance
- Bus termination or wiring harness damage (pinched, chafed)
Symptoms
- MIL (check engine) or dash warning lamp illuminated
- Messages relating to 12 V system or charging may be present
- Low accessory/auxiliary battery voltage or charge faults
- Loss of features that rely on DC/DC converter B
- Multiple communication-related DTCs in other modules
- Intermittent or no communication with module via scan tool
What to check
- Read all modules with a capable scan tool; note freeze frame and related U-codes
- Verify whether the code is current, history, or pending; clear and see if it returns
- Visually inspect the DC/DC converter module connector for corrosion, damage, or water ingress
- Check fuses and relays supplying the module power and key/switched feeds
- Measure supply voltage and ground at the module connector with key ON
- Check CAN/LIN wiring continuity and for shorts to battery/ground using a digital meter
Signal parameters
- Module supply voltage: ~11–14 V with key ON/engine running (verify vehicle spec)
- Ground resistance at module: ideally
- CAN bus idle (recessive): both CAN_H and CAN_L near ~2.5 V (vehicle-dependent)
- CAN bus dominant differential: approx. 2 V difference (typical CAN_H ~3.5 V, CAN_L ~1.5 V)
- Termination resistance: approx. 60 ohms measured across CAN_H–CAN_L (two 120Ω in parallel)
- Expected activity: visible CAN frames on oscilloscope/scan tool when module is communicating
Diagnostic algorithm
- Connect a professional scan tool and read all U-codes and related faults; record freeze frame.
- Clear the code and attempt to communicate with DC/DC Converter Control Module B using the scan tool.
- If module is not found, inspect fuses/relays and verify the module has proper supply voltage with key ON.
- Check module ground(s) for good connection and low resistance to chassis.
- Visually inspect the module connector and harness for damage, corrosion, bent pins, or water intrusion; repair as needed.
- Measure CAN_H and CAN_L voltages at the module connector (key ON). Verify termination resistance across the bus.
- Use an oscilloscope or bus analyzer to check for valid CAN frames and to identify noise, stuck dominant bits, or collisions.
- If the physical layer is good and no communication is possible, check for other modules causing bus contention; disconnect suspected nodes if safe to do so and recheck communications.
- If wiring, power, and grounds are intact but the module is unresponsive, consult OEM service information for reprogramming or known module updates; consider replacement only after confirming module failure.
- After repair, clear DTCs, verify module presence on the network, and perform a road test to ensure the code does not return.
Likely causes
- Blown fuse or missing 12 V supply to DC/DC Converter Control Module B
- Disconnected, corroded, or bent pins at the module connector
- Open or shorted CAN (or LIN) wiring near the module
- Poor ground at module chassis or ground strap
- Module internal failure preventing bus response
- Network termination fault or another module driving the bus
Fault status
Status
Lost Communication With DC/DC Converter Control Module B — module not responding on the vehicle network.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email