The steering angle of a vehicle is monitored using position sensors of an
electric motor of an electric power assisted steering (EPAS) system. A
position of the electric motor corresponding to the straight-ahead,
center position of the steering system is stored in non-volatile memory
during a steering calibration procedure, such as an end-of-line
calibration in a vehicle assembly plant. Following power loss due to a
dead battery, a steering angle zeroing procedure performed in a vehicle
stability control (VSC) system generates a center position with enough
accuracy to be within one electrical cycle of the motor. The pre-stored
electric motor position is then used to determine the electrical cycle
where the center position was located, and accurate monitoring of
steering angle is resumed.