CAN NETWORK · ABS · BODY CONTROL
A lost-communication code tells you that one controller did not receive the information it expected. The named module may be offline, but the cause can also involve its supply, wiring or the network path. Start by finding which controller reported the fault and which controllers still answer a scan.
Common network-code routes
- U0001 / U0002 high-speed CAN network or network-performance concerns.
- U0073 a controller reports a communication bus in an off state.
- U0100 / U0101 missing communication from engine / transmission control.
- U0121 / U0122 missing communication from ABS / vehicle-dynamics control.
- U0126 / U0131 missing communication from steering-angle sensing / power-steering control.
- U0140 missing communication from body control.
- U0110 / U0111 missing communication from drive-motor / battery-energy control A.
Names and detailed test procedures depend on vehicle implementation. Reference HELLA network code reference. We also have a focused U0100 and U0101 guide.
Why a complete scan matters
Keep the controller list, exact DTC text, status and available event data. Record whether the problem is permanent or intermittent. An engine-only reader may miss a useful body, brake or gateway report. Tell the team about recent battery work, water leaks, aftermarket equipment and disconnected modules.
Choose the next diagnostic route
For U0121, include the brake warning messages and any related wheel-speed or supply codes when contacting our ABS and ESP service. For U0140, describe affected lights, locking, wipers or other body functions and see BCM and BSI support. Several unrelated controllers disappearing together is a reason to discuss vehicle network diagnosis.
Before disconnecting anything
Have a technician follow the manufacturer’s isolation and testing procedure. This page is not a CAN pinout or an instruction to probe airbag or high-voltage circuits. If braking, steering or drive is affected, arrange appropriate assistance rather than continuing a test drive simply to reproduce the code.
Send AXION your diagnostic details
For a Didcot workshop enquiry or a suitable UK postal module assessment, send the vehicle model, year, engine or gearbox, full module label, complete scan report and a description of what happened. Include previous battery work, programming, water ingress or replacement parts. Please agree suitability before removing or posting a unit.