U0135 — Lost communication with front differential module

The vehicle's main computer cannot communicate with the front differential control module. This usually happens due to wiring issues, a faulty module, or network problems within the vehicle's communication system.

Common causes

The cause is almost always one of a few things. Here they are — U0135 rarely comes from anything outside this list:

• Damaged or corroded wiring/connectors to differential module
• Faulty front differential control module
• Network communication fault in vehicle CAN bus
• Blown fuse related to differential module power
• Software glitch or module needing reset

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Check and clean wiring connectors to differential module
2. Inspect fuses related to differential control module
3. Scan and reset fault codes, update software if available
4. Test or replace front differential control module
5. Inspect vehicle CAN bus wiring and repair as needed

That is what holds for U0135 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.