U0102 Lost Communication with Transfer Case Control Module
The U0102 code indicates that the vehicle's main control module (typically the PCM/ECM) has lost communication with the Transfer Case Control Module (TCCM). This module manages the transfer case in 4WD or AWD vehicles, controlling mode selection (2WD, 4WD High, 4WD Low, etc.). Communication occurs over the CAN bus, so the loss may be due to wiring faults, power supply issues, or internal module failure.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Open or short circuit in the CAN bus wiring (short to ground or voltage)
- Corroded, loose, or damaged TCCM connector
- Blown fuse or defective relay causing loss of power to the TCCM
- Internal failure of the Transfer Case Control Module
- Faulty CAN bus termination module
- Electromagnetic interference affecting communication wiring
3. Symptoms You Will Notice
- Check Engine Light or 4WD warning light illuminated
- Inability to shift between 2WD and 4WD modes
- Transfer case stuck in one mode or erratic operation
- Reduced traction or drivability issues
4. Step-by-Step Diagnosis
Scan for additional codes to confirm U0102 and check for related CAN bus codes
Inspect TCCM connector for corrosion, damage, or loose pins
Test power and ground circuits at the TCCM (check fuses and relays)
Check CAN bus wiring for opens, shorts, or high resistance using a multimeter
Verify CAN bus termination resistance (should be ~60 ohms with modules connected)
If all else is OK, suspect internal TCCM failure and replace module
5. Frequently Asked Questions
Is it safe to drive?▼
It is not recommended to drive with this code, as loss of communication may cause unpredictable transfer case behavior, potentially leading to loss of traction or driveline damage. Have the vehicle diagnosed promptly.
How much does it cost to fix?▼
Repair costs vary widely: from $100-$300 for a fuse or wiring repair, to $500-$1,200 for TCCM replacement including labor and programming.