The code U0102: Lost Communication with Transfer Case Control Module indicates a loss of communication with the Transfer Case Control Module, a critical component in vehicles with 4-wheel or all-wheel drive systems. This issue may arise due to problems with the module itself, wiring and connection faults, or grounding issues.
U0102 quick overview
| Meaning | U0102: Lost Communication with Transfer Case Control Module |
| Is it serious? | Yes, it is serious as it affects the vehicle’s ability to properly engage and manage 4WD or AWD functions, potentially impacting drivability and safety. |
| Possible causes | – Faulty or damaged Transfer Case Control Module (TCCM) – Wiring issues, including open or short circuits in the communication lines – Corroded or poor connections at the TCCM – Grounding issues – Faulty Powertrain Control Module (PCM) |
| How to diagnose? | Check Power and Grounds: Verify the power supply and grounding to the TCCM. Inspect Wiring and Connectors: Look for damaged, corroded, or loose wiring and connectors. Scan for Additional Codes: Use a diagnostic scanner to check for other related codes that could indicate a broader system issue. Check Module Communication: Verify if other modules in the vehicle are able to communicate with the TCCM. Test Communication Lines: Utilize a multimeter or oscilloscope to test the communication lines (CAN bus) for appropriate signals and voltage levels. Consult Wiring Diagrams: Reference vehicle-specific wiring diagrams for troubleshooting and diagnostics. Consider Module Replacement: If diagnostics point to a faulty TCCM, consider replacing or reprogramming it. |
U0102 Meaning
When you see the code U0102, it means your car’s computer can’t talk to the part that controls the 4-wheel or all-wheel drive system. This is important to fix because it can affect how well your car drives, especially in slippery or off-road conditions. The problem might be due to a bad control module, some wires being damaged or disconnected, or issues with how the module is powered or connected to the car’s ground. A mechanic will need to check the wiring, test the connections, and maybe replace the control module to fix it.
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How to fix U0102 – learn from mechanics
I looked into U0102 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: GMC
Vehicle Information
- 2011 GMC Sierra 1500 WT 4.3L
Issue + Repair History
- MIL (Malfunction Indicator Lamp) lights for traction and stability control systems, ABS lamp, and handbrake warning lamp on.
- Code indicating no communication with the transfer case module, although the truck is manual 4WD.
- All wheel speed sensors showed normal readings on scan tool, and the ABS pump is operational.
- Previously encountered similar problem due to wrong ABS pump, but this truck has the original pump.
Other OBD2 Codes + Test Results
- C0569: System configuration error
- C0561: Invalid serial data
- U0102: No communication with transfer case module
Suggestions from Community
- Check ABS module configuration and programming
- Inspect ground wire connection on the frame rail under the driver’s side
- Top off brake fluid and reset level sensor
- Verify U codes or incorrect VIN in ECM, TCM, BCM, and ABS
- Reprogram modules with correct calibrations for manual transfer case
Final Fix
- Replaced ABS pump and performed a bleed procedure with a scan tool.
- No more warning lamps illuminated after the fix.
Case #2: Chevrolet
Vehicle Information
- 2008 Chevrolet Avalanche LS 5.3L
Issue + Repair History
- Vehicle displayed “service 4 wheel drive” message. Issue persisted after changing the battery.
- Unable to communicate with the 4WD shift module, but could communicate with PCM, BCM, ABS, etc.
Other OBD2 Codes + Test Results
- B1001: Option configuration error
- U0102: Lost communication with transfer case
Suggestions from Community
- Test powers and grounds to the TCCM (Transfer Case Control Module) using a headlight for a reliable load test.
- Disconnect TCCM fuse for 30 minutes as a potential reset method.
- Check for data on the communication line after disconnecting TCCM.
- Consider the possibility of a shorted encoder motor affecting the TCCM.
- Measure resistance at the DLC from terminal 6 to 14 for data wiring integrity.
- Replace TCCM if power, ground, and data wiring are confirmed to be okay.
Final Fix
- After isolating and inspecting wiring and modules, found no activity on the high-speed line, narrowed down to the black #4 BCM connector.
- Took the truck to the dealer to have a BCM installed and programmed. The problem ended up being both the BCM and the TCCM.
Case #3: Chrysler
Vehicle Information
- 2008 Chrysler Pacifica Touring 4.0L
Issue + Repair History
- Extended crank time before starting, no injector or ignition pulses during cranking. Once started, runs fine. Problem occurs both hot and cold.
- Replaced cam and crank sensors (aftermarket and OEM), new PCM installed. Wiring checked for opens or shorts. Cam tone ring checked.
Other OBD2 Codes + Test Results
- P0339: Crankshaft position sensor intermittent
- U0114: Lost communication with final drive control module
- U0102: Lost communication with transfer case control module / AWD
Suggestions from Community
- Ensure tone wheel on left camshaft sprocket isn’t loose or broken.
- Check tone ring.
- Check TPS readings during cranking for possible false “clear flood mode”.
- Ensure the flexplate tone ring is not bent or damaged.
- Consider possible issues with transmission temperature sensor.
Final Fix
- The flexplate tone ring was bent inward, causing sensor reading issues. The engine had been replaced by another shop, and the tone ring had been damaged during that process. Once fixed, the starting issue was resolved.
Case #4: Dodge
Vehicle Information
- 2005 Dodge Dakota ST 3.7L
Issue + Repair History
- No communication on CAN C. Only modules on CAN C are PCM, ABS, and front control module. Problem persists with two different PCMs. All modules on the bus have communication codes.
Other OBD2 Codes + Test Results
- U0102: CAN C communication
- U101: CAN C communication
- Voltage drop tested power and grounds – Ok
- CAN C resistance – 60 ohms
- CAN C voltage – 2.5 volts on CAN high and low
Suggestions from Community
- Check the fuel pump for potential shorting issues.
- Verify TCM module communication and examine power/ground connections.
- Investigate BCM response.
- Check power and grounds to TCM module.
- Consider possible issues with transfer case control module or front control module.
Final Fix
- The problem was traced to a second faulty PCM, where the second terminating resistor is located. After replacing the PCM, the communication issues were resolved.
Case #5: GMC
Vehicle Information
- 2010 GMC Sierra 1500 WT 4.3L
Issue + Repair History
- ABS and Stabilitrac lamps on. U0102 (transfer case, no communication) and C0455 (steering position sensor) codes present. Truck is 2-wheel drive. All wheel speed sensors read correctly, and ABS pump operates normally.
Other OBD2 Codes + Test Results
- U0102 – Transfer case, no communication
- C0455 – Steering position sensor
- C0569 – System configuration fault
Suggestions from Community
- Reprogramming the ABS module for 2WD configuration.
- Replacing the steering angle sensor for the C0455 code.
- Checking power and ground connections.
- Investigating harness connections and possible corrosion.
- Considering reprogramming or replacement of the EBCM (Electronic Brake Control Module).
Final Fix
- The issue was resolved by replacing the EBCM, which had been previously replaced with the wrong part. This mismatched part did not have the feature to turn off traction control, which was present in the truck. After installing the correct EBCM, the warning lights were resolved.
How to diagnose U0102
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Advice | Description of Diagnostic Step |
|---|---|
| Check Power and Grounds | Verify power and ground connections at the PCM and related modules to ensure there’s no voltage drop or connectivity issues. |
| Examine Wiring and Connectors | Inspect wiring harnesses and connectors for damage, corrosion, or loose connections that could affect communication. |
| Reprogram or Replace PCM | If the PCM is new or replaced, ensure it’s properly programmed. If still unresolved, consider replacing the PCM. |
| Inspect Tone Ring or Flexplate | Examine the tone ring or flexplate for damage, bending, or incorrect positioning that could affect sensor readings. |
| Verify Software Calibration | Ensure the latest software calibration is installed in the PCM or relevant control modules. |
| Test Communication Lines | Utilize a scope or multimeter to test the communication lines (CAN bus) for proper voltage levels and signals. |
| Reset or Relearn Procedures | Perform necessary reset or relearn procedures after parts replacement or when diagnosing communication issues. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko