What does this code mean?
The wording below belongs to the named make and communication. Match the complete code, reporting module, model year and engine before applying it.
A code identifies a detected condition, not a part that must automatically be replaced.
Manufacturer communications
3Original wording in English
CADILLAC, CHEVROLET, GMC, HUMMER
Reported code forms U0121
This technical bulletin provides repair information to correct customer concerns of loss of high speed GMLAN communications, intermittent no crank, IP gauge fluctuation, intermittent door lock cycling /chime operation,…
CADILLAC, CHEVROLET, GMC, HUMMER
Reported code forms U0121
GM: LOSS OF HIGH SPEED GMLAN COMMUNICATIONS, INTERMITTENT NO CRANK, IP GAGE FLUCTUATION, INTERMITTENT DOOR LOOK CYCLING, INTERMITTENT CHIME OPERATION, VARIOUS IP WARNING LAMPS ILLUMINATED, TRANSMISSION MAY NOT SHIFT,…
CADILLAC, CHEVROLET, GMC
Reported code forms U0121
LOSS OF HIGH SPEED GMLAN COMMUNICATIONS, INTERMITTENT NO CRANK, IPC GAUGE FLUCTUATION, INTERMITTENT DOOR LOCK CYCLING, TRANSMISSION MAY NOT SHIFT, DTCS U0073, U0100, U0101, U0102, U0121, U0140 SET (REPAIR BACKED OUT…
Check vehicle applicability
3A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Historical vehicle association; OBD-II compatibility is not established by this record.
Historical records · 243 · Historical vehicle association; OBD-II compatibility is not established by this record.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.