I was not sure my self? So I asked around a few colleagues and I got this back.
U1120 = Lost Wheel Distance Message. The set condition = the PCM doesn't receive a wheel distance message from the Anti-lock brake module over the CAN C bus. The CAN (Controller Area Network) C is a high speed bus that used for large data transfer. The following systems us CAN C: PCM, ABS and TCM. If that's your only code, then I'd start with the ABS module. The most likely cause is a bad wheel speed sensor, so check those.