Code :  C1223
Make :  BUICK
Description :  C1223 BUICK Left Rear Wheel Speed Sensor Input Signal Is Zero
Possible causes : 
   – Faulty Hub Assembly (Left Rear Wheel Speed Sensor is part of hub assembly)
   – Faulty Left Rear Wheel Speed Sensor
   – Left Rear Wheel Speed Sensor harness is open or shorted
   – Left Rear Wheel Speed Sensor circuit poor electrical connection
Solutions : 
   – Carry out a Reset via CarDiag
   – Choose a better quality fuel
   – Check that the tank cap is securely closed
   – Check the oil level and add more if it is lower than MAX
   – Restart an Automatic diagnostic via CarDiag
   – If the fault persists, you can check the “Possible causes” listed above : visually inspect (by yourself (tutorials to come) or by a professional) the wiring harness and the associated connectors, check for damaged components, and look for broken, bent, pushed, or corroded connector pins.
