OBD-II trouble code
U0135: Lost Communication With Differential Control Module — Front
The front differential control module has gone silent on the network — common on 4WD/AWD vehicles with electronically controlled front axles or lockers.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $50 – $900
- DIY difficulty
- Advanced DIY
What does U0135 mean?
Four-wheel-drive and AWD vehicles with electronically controlled front differentials — actuated lockers, disconnecting front axles, or torque-managed diffs — use a control module to manage that hardware. U0135 sets when the rest of the network stops receiving that module's messages. Its rear counterpart is U0136 (Lost Communication With Differential Control Module — Rear).
The cause hierarchy is standard for lost-communication codes: power or ground loss to the module (fuse, corroded feed), connector or CAN wiring damage, then the module itself. Front differential modules and their connectors live low in the driveline area, taking spray, mud, and vibration, so environmental wiring damage leads the list in the real world. Low battery voltage during cranking can set network codes spuriously — verify basics first.
While the module is offline the driveline defaults to a safe mode: typically the front axle stays disengaged or the diff stays open, 4WD modes may refuse to engage, and a driveline warning shows. The vehicle remains drivable as (effectively) two-wheel drive.
Common causes
- Blown fuse or lost power/ground to the front differential module
- Corroded or mud/spray-damaged connector in the driveline area
- Damaged CAN bus wiring to the module
- Failed front differential control module
- Low system voltage during cranking
Symptoms
- 4WD/AWD or driveline warning light/message
- 4WD modes won't engage; front axle/locker inoperative
- Code stored in other modules (TCCM, PCM, ABS)
- Vehicle drives normally in 2WD
Diagnostic steps
- 1.Check battery and charging voltage first.
- 2.Attempt direct scan-tool communication with the differential/4WD module.
- 3.Check the module's fuses and power/ground circuits.
- 4.Inspect connectors and harness in the front driveline area for corrosion, mud packing, or chafe.
- 5.Verify CAN bus integrity to the module (resistance/waveform where possible).
- 6.Replace and program the module only after feeds and wiring prove good.
Repair cost
$50 – $900
Most fixes are fuses, grounds, and connector repairs at modest cost. Module replacement with programming typically runs $300-$900 by platform. Off-road-used vehicles should get a hard look at physical harness damage first.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with control module replacement & programming preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.