DIAGNOSIS The "Suds" or "SD" error means the washer's sensor detected too many suds during a rinse cycle. Even with HE detergent, using too much is the number one cause.
FIX You need to clear the suds. Run a Rinse & Spin cycle. If the error persists, you may need to manually bail out some water/suds from the drum and run the cycle again. Long-term, drastically reduce your detergent dose. For an average load, use no more than two tablespoons of HE liquid or the lowest line in an HE powder scoop.
IF THAT DIDN'T WORK The type of detergent matters. Some "natural" or homemade detergents, and definitely regular (non-HE) detergent, create excessive suds in high-efficiency machines. Make absolutely sure your detergent bottle has the official "HE" symbol on it.
HEADS UP Fabric softener and dryer sheets can leave a waxy residue on the suds sensor, making it overly sensitive and trigger the error falsely. If you use them, try stopping for a few weeks to see if the errors go away.