Code
U0148
Generic
U — Network/User
Lost Communication With Serial Data Gateway Module C
Views:
UK: 22
EN: 20
RU: 17
AI status
Completed
Completed
100%
Causes
- Faulty Serial Data Gateway Module C (internal failure)
- Open/short/intermittent wiring or connector between gateway and power/ground or network
- Blown fuse or faulty relay supplying the gateway
- Low battery voltage or poor battery/ground connections
- CAN/serial data bus fault (short to Vb or ground, open, high resistance, missing termination)
- Software/firmware corruption or required module programming/update
Symptoms
- Multiple systems inoperative or limited operation that rely on gateway routing
- Instrument cluster, infotainment, HVAC, keyless entry, or other modules not responding or showing errors
- Diminished or no communication with some controllers on scan tool (module appears missing)
- Intermittent functionality that may change with vibration or temperature
- Possible stored network communication DTCs for other modules
What to check
- Verify battery voltage is 12.4–12.8 V (engine off) and test while cranking; charge if low
- Connect a scan tool and list modules present on all networks; note which modules are missing
- Read freeze frame and pending codes; record other U-codes present
- Visually inspect harness, connectors, and module for corrosion, water ingress, or physical damage
- Check fuses and relays that supply power/ignition to the gateway and related modules
- Backprobe power and ground pins at the gateway connector; verify good grounds and stable 12 V supply
Signal parameters
- Battery supply to module: ~12 V (key on); must be stable under load
- CAN bus idle common-mode: ~2.5 V; CAN_H recessive ~2.5 V rising to ~3.5 V when dominant; CAN_L recessive ~2.5 V dropping to ~1.5 V when dominant
- Differential CAN voltage: ~0 V (recessive) to ~2 V (dominant) across CAN_H and CAN_L
- Typical CAN data rates: 125 kb/s, 250 kb/s, 500 kb/s (verify vehicle-specific rate)
- LIN bus idle ~12 V (or battery) with data pulses to ground (if gateway uses LIN segments)
- Termination resistance on CAN: ~60 Ω measured across CAN_H and CAN_L with key on (vehicle-specific)
Diagnostic algorithm
- Confirm battery state-of-charge and good chassis/engine grounds; recharge or replace battery if undervoltage.
- Use a scan tool to identify which modules are present/missing, and record all DTCs and freeze frame data.
- Inspect connectors and wiring to the gateway and related modules for damage, corrosion, or water entry; repair any damage.
- Verify power and ground at the gateway connector: backprobe the fused power feed(s) and ground(s) with key on. Repair open/poor connections.
- Check fuses/relays feeding the gateway and related circuits; replace any blown fuses and verify relay operation.
- Measure CAN_H and CAN_L voltages and differential with key on. Look for short to battery/ground, open circuit, or stuck dominant state.
- Measure termination resistance across CAN_H and CAN_L; isolate network segments if termination is incorrect to find fault location.
- Perform wiggle tests on harnesses while monitoring network presence to find intermittent faults. Use scope for transient issues if needed.
- If wiring and power/ground are good but gateway is unresponsive and reports internal faults, consult OEM service info for module reprogramming or replacement procedures.
- After repairs, clear codes, re-scan and perform functional verification of affected systems; road test to confirm repair.
- Note: follow vehicle-specific service manual for pinouts, wiring diagrams, and module programming precautions. Do not replace modules unless diagnostics point to a failed unit.
Likely causes
- Loose/poor ground or low battery voltage preventing gateway operation
- Damaged or disconnected network wiring or chafed harness near doors/engine bay
- Corroded connector pin(s) at the gateway or PDC/fuse block
- Failed gateway module due to internal electronics or water intrusion
Fault status
Status
Lost communication with Serial Data Gateway Module C — the gateway is not responding on the vehicle serial/CAN network.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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Code
U0148
HYUNDAI
U — Network/User
Lost Communication With Gateway “C”
Views:
UK: 8
EN: 10
RU: 12
AI status
Completed
Completed
100%
Causes
- Faulty Serial Data Gateway Module C (internal failure)
- Open/short/intermittent wiring or connector between gateway and power/ground or network
- Blown fuse or faulty relay supplying the gateway
- Low battery voltage or poor battery/ground connections
- CAN/serial data bus fault (short to Vb or ground, open, high resistance, missing termination)
- Software/firmware corruption or required module programming/update
Symptoms
- Multiple systems inoperative or limited operation that rely on gateway routing
- Instrument cluster, infotainment, HVAC, keyless entry, or other modules not responding or showing errors
- Diminished or no communication with some controllers on scan tool (module appears missing)
- Intermittent functionality that may change with vibration or temperature
- Possible stored network communication DTCs for other modules
What to check
- Verify battery voltage is 12.4–12.8 V (engine off) and test while cranking; charge if low
- Connect a scan tool and list modules present on all networks; note which modules are missing
- Read freeze frame and pending codes; record other U-codes present
- Visually inspect harness, connectors, and module for corrosion, water ingress, or physical damage
- Check fuses and relays that supply power/ignition to the gateway and related modules
- Backprobe power and ground pins at the gateway connector; verify good grounds and stable 12 V supply
Signal parameters
- Battery supply to module: ~12 V (key on); must be stable under load
- CAN bus idle common-mode: ~2.5 V; CAN_H recessive ~2.5 V rising to ~3.5 V when dominant; CAN_L recessive ~2.5 V dropping to ~1.5 V when dominant
- Differential CAN voltage: ~0 V (recessive) to ~2 V (dominant) across CAN_H and CAN_L
- Typical CAN data rates: 125 kb/s, 250 kb/s, 500 kb/s (verify vehicle-specific rate)
- LIN bus idle ~12 V (or battery) with data pulses to ground (if gateway uses LIN segments)
- Termination resistance on CAN: ~60 Ω measured across CAN_H and CAN_L with key on (vehicle-specific)
Diagnostic algorithm
- Confirm battery state-of-charge and good chassis/engine grounds; recharge or replace battery if undervoltage.
- Use a scan tool to identify which modules are present/missing, and record all DTCs and freeze frame data.
- Inspect connectors and wiring to the gateway and related modules for damage, corrosion, or water entry; repair any damage.
- Verify power and ground at the gateway connector: backprobe the fused power feed(s) and ground(s) with key on. Repair open/poor connections.
- Check fuses/relays feeding the gateway and related circuits; replace any blown fuses and verify relay operation.
- Measure CAN_H and CAN_L voltages and differential with key on. Look for short to battery/ground, open circuit, or stuck dominant state.
- Measure termination resistance across CAN_H and CAN_L; isolate network segments if termination is incorrect to find fault location.
- Perform wiggle tests on harnesses while monitoring network presence to find intermittent faults. Use scope for transient issues if needed.
- If wiring and power/ground are good but gateway is unresponsive and reports internal faults, consult OEM service info for module reprogramming or replacement procedures.
- After repairs, clear codes, re-scan and perform functional verification of affected systems; road test to confirm repair.
- Note: follow vehicle-specific service manual for pinouts, wiring diagrams, and module programming precautions. Do not replace modules unless diagnostics point to a failed unit.
Likely causes
- Loose/poor ground or low battery voltage preventing gateway operation
- Damaged or disconnected network wiring or chafed harness near doors/engine bay
- Corroded connector pin(s) at the gateway or PDC/fuse block
- Failed gateway module due to internal electronics or water intrusion
Fault status
Status
Lost communication with Serial Data Gateway Module C — the gateway is not responding on the vehicle serial/CAN network.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
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