Conditions for Setting the DTC
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
DTC C056E 42
This DTC will set if the PSCM has not undergone SPS programming.
DTC C056E 4B
This DTC will set if the PSCM, motor or torque sensor has not been calibrated using the steering position / torque sensor calibration procedure.