CAN high / low assessment
Voltage and communication checks on accessible network circuits.
CAN bus · U-codes · modules offline · network diagnosis
CAN Bus & No Communication Diagnostics
Vehicle-network diagnostics for control modules that go offline, generate U-codes or create multiple warning lights because communication between controllers has been interrupted.
✓ Vehicle-specific checks✓ Controlled programming✓ Clear verification
CAN high / low checksU-code diagnosisOffline module testingIntermittent network faults
Vehicle network diagnostics
One network fault can make several modules look faulty.
CAN and LIN networks allow control units to share data. A shorted line, poor supply, damaged connector or faulty controller can disturb the network and trigger faults in systems that are not themselves defective.
We use scan information and electrical measurements to narrow the fault before recommending module replacement or programming.
Before we program anything
✓Vehicle and module identification checked
✓Diagnostic fault information reviewed
✓Compatibility confirmed where possible
✓Programming route selected for the exact job
Workshop & bench work
Network diagnosis needs more than clearing U-codes.
The useful question is which module or circuit is disturbing communication, not simply which controller recorded the fault.
Network scan
A full-system scan identifies modules that are offline or reporting communication faults.
Electrical testing
Voltage, resistance, grounds and connector condition are checked before condemning a module.
Power & CAN checks
Battery supply, fusebox circuits and network behaviour are tested together.
Module communication
Individual control units can be isolated when one module is pulling the network down.
Service options
CAN and communication checks.
Testing is tailored to the topology and symptoms of the vehicle.
Module-offline diagnosis
Power, ground and network checks for controllers that cannot be reached.
Gateway faults
Communication pathways reviewed where multiple networks meet.
Intermittent communication
Fault history, live behaviour and connector condition considered together.
Typical enquiries
When CAN bus diagnosis is appropriate.
Network faults often create broad or intermittent symptoms.
Several modules report U-codes
Communication faults appear across different systems.
ECU will not communicate
One controller is completely absent from the scan.
Warning lights appear together
ABS, steering, engine and body warnings arrive at the same time.
Fault changes when vehicle moves
Harness, connector or intermittent network issues may be involved.
Specialist support
Find the network cause before replacing modules.
A module reporting 'no communication with X' does not prove that X is faulty. The missing controller may have lost power, ground or network connectivity.
Full-system scan
See which modules are online and how the fault is distributed.
Electrical measurements
Check network and supply conditions rather than relying on codes alone.
Isolation strategy
Where practical, suspect branches or controllers are tested methodically.
Programming only if needed
Software or coding follows the diagnosis, not the other way around.
Identify. Diagnose. Program. Verify.
Map the symptom
Review which systems fail and when the fault appears.
Scan the network
Record online modules, U-codes and gateway information.
Test circuits
Check accessible network, power and ground conditions.
Confirm repair route
Identify wiring, connector, module or programming work required.
Network diagnosis can be time-consuming because faults may be intermittent and several modules can report secondary communication codes. Testing is quoted according to the complexity of the vehicle and fault.
Need a compatibility check?