Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
CADILLAC, CHEVROLET, GMC
Reported code forms U0121
This Preliminary Information communication provides information to the technician about vehicle with Service ABS and/or Traction control lights/message on, Service Power Steering System, Service Suspension System, and…
CADILLAC, CHEVROLET, GMC
Reported code forms U0121
This Preliminary Information communication provides information to the technician for a reduced power message, steering assist, engine stall or the instrument panel, radio, and or Heater-Vent-Air Conditioning go blank…
CADILLAC, CHEVROLET, GMC
Reported code forms U0121
This Preliminary Information communication provides information to the technician about vehicle with Service ABS and/or Traction control lights/message on, Service Power Steering System, Service Suspension System, and…
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
Reported code forms U0121
This Preliminary Information communication provides information to the technician for a reduced power message, steering assist, engine stall or the instrument panel, radio, and or Heater-Vent-Air Conditioning go blank…
CADILLAC, CHEVROLET, GMC
Reported code forms U0121
GMC: UNABLE TO COMMUNICATE WITH THE EBCM DTC U0121. *NJ VEHICLES EQUIPPED WITH JL4. UPDATED 9/30/08. *PE UPDATED 6/27/11. *PE UPDATED 4/6/12. *PE
CADILLAC, CHEVROLET, GMC
Reported code forms U0121
IGNITION SWITCH DIAGNOSTIC TIPS - DTC CODES C0561, P1629, P1682, U0101, U0121, U0155 AND/OR NO CRANK/NO START, HVAC, RADIO, ON STAR, POWER ADJUSTABLE PEDALS, AND OTHER ELECTRICAL COMPONENTS INOPERATIVE. *KB