U0102

Code

HYUNDAI U — Network/User

Lost Communication with Transfer Case Control Module

Brand: HYUNDAI

Type: U — Network/User

Views: UK: 15 EN: 18 RU: 29

AI status

Completed

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Page language: EN

Causes

Open or shorted CAN bus wiring between TCCM and main network
Faulty Transfer Case Control Module (TCCM)
Blown fuse or loss of TCCM power/ground
Corroded or disconnected connector at TCCM
Network bus off condition caused by another module
Software/memory fault or incompatible module programming

Symptoms

Transfer case functions unavailable or stuck in one mode (2WD/4WD/Auto)
Illuminated warning lamps (ABS, ESC, 4WD/AWD, check engine) or message on cluster
Loss of related features controlled by transfer case (hill descent, AWD torque distribution)
No TCCM module response when scanned with diagnostic tool
Intermittent network-related faults or communication interruptions

What to check

Use a capable scan tool to confirm U0102 and check for other network codes
Verify battery voltage is within specification and key ON state
Visually inspect TCCM connector for corrosion, bent pins, or moisture
Check related fuses and relay supplying TCCM power
Monitor CAN bus data — confirm presence of other modules and bus health
Perform wiggle test on wiring while watching for communication changes

Signal parameters

CAN High / CAN Low differential voltages: ~2.5 V idle, ~3.5 V/1.5 V dominant levels (vehicle off vs on varies)
Presence and frequency of TCCM-specific CAN messages (module ID/message ID varies by model)
Bus error counters or 'bus off' status from scan tool
Supply voltage to TCCM (battery voltage at module, ~12 V nominal)
Module ground resistance (low, ideally

Diagnostic algorithm

Connect manufacturer-level scan tool; record U0102 and any other U-codes. Check module list to see if TCCM is present on the network.
Verify battery voltage and charge if low. Re-check DTC after proper battery voltage restored.
Inspect TCCM connector: disconnect, inspect pins for corrosion, bent pins, water ingress; reseat with dielectric if needed.
Check fuses/relays for TCCM power sources. Verify 12 V supply and ground at the module with key ON.
Probe CAN-High and CAN-Low at the TCCM connector with an oscilloscope or DVM to confirm expected voltages and differential signals. Compare with another known-good module location.
If CAN signals absent or abnormal, trace wiring for opens/shorts to ground or battery. Repair any damaged wiring or connectors.
If CAN signals present and power/ground OK but module not responding, try performing an ignition cycle and clear codes. Re-scan for return.
If intermittent, perform wiggle tests along harness while monitoring communication; repair any intermittent connections.
Check for other modules reporting bus errors; isolate a faulty module by disconnecting suspected harness branches and observing if bus recovers.
If wiring and power are good and the module never communicates, verify software level/programming. Reprogram or replace TCCM per factory procedures and re-initialize as required.
After repairs, clear DTCs, perform a road test and re-scan to confirm the fault does not return.

Likely causes

Loose, corroded, or damaged TCCM connector or pins
Damaged CAN-High or CAN-Low wiring (chafing, rodent, pinched)
No battery feed or bad ground at TCCM
Replacement TCCM not programmed or VIN mismatch
Short to voltage or ground on CAN lines from other faulting module

Fault status

⚠️ Status

U0102 — Lost Communication with Transfer Case Control Module. The vehicle network is not receiving expected messages from the transfer case module; module may be unpowered, disconnected, faulty, or the CAN bus may be compromised.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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