U0046

Code

HYUNDAI U — Network/User

Vehicle Communication Bus C

Brand: HYUNDAI

Type: U — Network/User

Views: UK: 13 EN: 12 RU: 14

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or short in CAN Bus C wiring (CAN_H/CAN_L)
Faulty module or CAN transceiver on Bus C
Missing or damaged termination resistor(s)
Poor power or ground to one or more modules on Bus C
Corroded or disconnected connectors, water intrusion
Intermittent wiring harness damage from chafing or pinched cable

Symptoms

Multiple modules not communicating or responding to scan tool
Inoperative or intermittent vehicle systems tied to Bus C
MIL (check engine) and other warning lamps illuminated
Erratic or missing instrument cluster messages
Stored U-codes from multiple modules referencing bus communication
Vehicle may enter limp-home or reduced functionality mode (depending on affected modules)

What to check

Use a scan tool to read all U-codes and note which modules are not responding
Record freeze frame and time-since-code data and look for related codes
Visually inspect wiring, connectors and modules on Bus C for corrosion, damage or water
Check battery voltage and main power/ground integrity (low battery can affect network)
Measure resistance between CAN_H and CAN_L with ignition off (expected ~60 Ω total termination)
Measure CAN_H and CAN_L idle voltages with ignition ON (see signal parameters)

Signal parameters

Termination resistance between CAN_H and CAN_L: ~60 Ω (two 120 Ω terminators in parallel)
Recessive (idle) voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V
Dominant state voltages (approx): CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Differential voltage during data: ≈ 1.0–2.5 V depending on network
Bit rate and exact voltage levels vary by vehicle — confirm CAN bus speed and parameters from Hyundai service information

Diagnostic algorithm

Connect a factory-level scan tool. Record all present U-codes and identify which control modules fail to communicate on Bus C.
Check vehicle battery voltage and charging system; ensure stable supply during diagnostics.
Visually inspect all connectors and wiring harnesses related to Bus C nodes (look for corrosion, water, pin damage).
With ignition OFF, measure resistance between CAN_H and CAN_L at a convenient connector. Expect ~60 Ω. If open or very high, look for open circuit; if very low, look for short.
With ignition ON, measure idle voltages of CAN_H and CAN_L relative to chassis ground. Compare to expected values in signal parameters.
Use an oscilloscope or high-speed CAN data logger to view bus waveform and check for noise, missing recessive states, or repeated dominant frames indicating shorted/grounded line or stuck node.
Isolate sections of the bus: disconnect suspected module connectors one at a time (with ignition off where required by procedure) to see if fault clears, indicating a problematic node.
Check power and ground feeds to all modules on Bus C. Repair any poor connections or corroded grounds.
Repair or replace damaged wiring, connectors, or terminating resistors as required. Clear codes and test-drive to confirm repair.
If wiring and terminations are good but communications still fail, suspect a failed module transceiver. Replace or reprogram modules only after confirming they are the root cause and following OEM programming procedures.
After repairs, re-scan all modules, confirm network stability, and ensure no related codes return.

Likely causes

Damaged CAN_H or CAN_L conductor (open/short to ground or battery)
Failed CAN transceiver in a control module on Bus C
Lost ground or supply to the network wiring or a node
Removed or failed termination resistor(s) causing bus reflections
Connector corrosion or loose pin at a module connector
Recent module replacement with incorrect programming

Fault status

⚠️ Status

U0046 - Vehicle Communication Bus 'C' Fault / Lost Communication

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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