What does it mean?
U1260 is a Network (CAN bus, module communications) fault code. It indicates: Data Circuit Message .
Symptoms
- Scan tool connects slowly, drops out, or cannot see some modules
- Several unrelated warning lamps come on together
- Comfort features fail intermittently — central locking, windows, lighting, cluster
- Gauges sweep, freeze or fall to zero
- Battery drains because modules stay awake
- Faults appear and disappear with road bumps or temperature changes
Likely causes
- Open circuit in the bus positive wire, most often at a splice or a previous repair joint
- Bus positive wire shorted to ground, forcing the network into single-ended operation
- Bus positive shorted to battery voltage after chafing against a power feed
- Corroded or spread terminal on the bus positive pin at a module or at the diagnostic connector
- Water inside a connector bridging the two bus wires
- A module with an internal fault pulling the positive line down
- Harness damage after accessory fitment, body repair or rodent activity
How to fix it
- Scan all modules and write down which respond, to map the affected branch
- Inspect the diagnostic connector pins for damage or push-back from previous tool use
- With the ignition off, check the bus positive wire end to end for continuity and for short to ground and to battery
- Wiggle-test the harness section by section while watching the scan tool link
- Open the splice packs and inspect for green corrosion; repair by soldering and sealing
- Disconnect modules one at a time to find one that is loading the line
- Replace a module only once the wiring has been proven clean