U0102
Lost Communication With Transfer Case Control Module
Communication network (CAN bus)
Generic OBD-II
Medium
What it means
U0102 means another module has stopped receiving messages from the transfer case control module — the unit that manages 4WD/AWD shifting. The engine still runs and the vehicle drives, but four-wheel drive may be disabled or stuck in one mode. It usually points to a wiring, connector, power/ground, or bus fault at the module, or a failed module itself.
Medium
Can I keep driving? Usually yes — the engine runs and you can drive, but 4WD/AWD shifting may be disabled or stuck in one mode; avoid relying on four-wheel drive until it's fixed.
Common symptoms
What you'll notice
- 4WD/AWD or service-4WD warning light on
- Can't shift between 2WD, 4WD-high, and 4WD-low, or the system is stuck in one mode
- Transfer case dash indicators blank or flashing
- Other modules may log lost-communication codes for the transfer case module
Common causes
Most likely first
- Wiring or connector fault at the transfer case control module (opens, corrosion, damage)Likely
- Loss of power or ground to the moduleCommon
- CAN bus wiring fault on the branch feeding the moduleCommon
- Water intrusion at the module or its connector (common in an exposed location)Less often
- Failed transfer case control moduleLess often
How to diagnose & fix
Work through it in order
- Scan all modules to confirm it's specifically the transfer case module that's offline.
- Check power and ground at the module connector with the key on.
- Inspect the module's wiring and connector for corrosion, damage, or water intrusion.
- Test the CAN bus continuity between the module and the rest of the network.
- If power, ground, and bus wiring are good, the module itself is likely failed — replace and program as needed, then re-test.
FAQ
Quick answers
Is it safe to drive with U0102?+
You can drive, but four-wheel drive may not engage or disengage on demand. Don't count on 4WD in low-traction conditions until the fault is repaired.
Can I just clear U0102?+
It clears, but returns if there's a wiring, power, or module fault. If it was a one-time glitch it may stay away — but recurring codes need the cause fixed.
Related codes
Often seen with U0102
Read & clear U0102 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX