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.

Real-world scan data

Seen in

300

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of U0102 scans

B1322in 49.7% of scans

B1A28in 49.3% of scans

U1112in 45.3% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear U0102 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX