What does it mean?
U1223 is a Network (CAN bus, module communications) fault code. It indicates: CAN-HS VDC/ABS No-Receive Data . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- ABS, traction control and stability control lamps illuminated together
- Brakes still work but there is no ABS assistance in an emergency stop
- Speedometer reads zero or drops out intermittently
- Cruise control and hill-hold assist unavailable
- Steering may feel heavier on systems that use vehicle speed data
- Scan tool cannot connect to the ABS module
Likely causes
- ABS control module without power or ground; its dedicated fuses are the first place to look
- Open or shorted high-speed CAN wires between the ABS module and the rest of the network
- Corroded or water-damaged ABS module connector, common in the wheel arch and front chassis area
- Internal failure of the ABS / vehicle dynamic control module
- Missing or failed terminating resistor causing reflections on the bus
- Harness damage at the front of the vehicle after a minor collision, curb strike or rodent activity
- Very low battery voltage or a poor main ground making the module reset
How to fix it
- Scan every module and confirm that only the ABS unit is missing from the network
- Check the ABS fuses and relays, then measure supply voltage and ground at the module connector
- With the ignition off, measure resistance across CAN high and CAN low at the diagnostic connector
- Inspect the ABS module connector for water, corrosion and pushed-out terminals
- Backprobe the CAN pins at the ABS module and confirm the normal bus voltage levels
- Repair damaged bus wiring with soldered and sealed joints, never with twisted taps
- Replace and configure the ABS module only after wiring and supply tests pass