U0148

Code

Generic U — Network/User

Lost Communication With Serial Data Gateway Module C

Brand: Generic

Type: U — Network/User

Views: UK: 32 EN: 42 RU: 27

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Page language: EN

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

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

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

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)

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.