What does it mean?
U1209 is a Network (CAN bus, module communications) fault code. It indicates: Manufacturer-Specific CAN/Network Bus Fault . 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
- Power seat does not move at all, or only some directions work
- Memory positions are not stored or not recalled
- Seat heating or lumbar support fails at the same time
- Seat moves by itself or stops part way through its travel
- Warning lamp on the dash with other network codes stored
- Scan tool cannot communicate with the seat module
Likely causes
- Faulty power seat or memory seat switch pack sending an out-of-range signal
- Chafed wiring in the under-seat harness, which flexes every time the seat is moved
- Under-seat connector unplugged or corroded after seat removal or carpet cleaning
- Seat module loses power or ground and stops broadcasting on the bus
- Water damage from a spilled drink or a leaking door seal reaching the under-seat connector
- Fault in the bus wiring itself, so the seat data never reaches the receiving module
- Seat module replaced without configuration, or an internal driver failure
How to fix it
- Scan all modules and check whether the seat module answers at all
- Watch the switch live data while operating each direction in turn
- Slide the seat fully forward and back and inspect the harness for pinched, stretched or rubbed wires
- Unplug and inspect the under-seat connectors for corrosion, moisture and pushed-back terminals
- Measure supply voltage and ground at the seat module while the switch is operated
- Test the switch pack for continuity in every position with a multimeter
- Repair the harness or replace the switch; configure the module if it has been replaced