Warning Light Shows An "Unlatch" Signal Although Shoulder Belt Is Properly Latched To Anchor

Check shoulder belt buckle switch. Disconnect shoulder belt buckle switch connector. Latch shoulder belt to anchor and move anchor to rear end. Measure resistance between buckle switch's terminals. See Figure. Resistance should be: No.3 to No.4/1 MOhm min. If not okay, replace shoulder belt buckle switch (complete with rear limit switch). If okay, proceed.
Check shoulder belt buckle switch harness. Disconnect connector from control unit. Disconnect buckle switch connector. Measure resistance between buckle switch connector and body. Resistance should be: R16 No.4 to Body/1 MOhm min. R25 No.4 to Body/1 MOhm min. If not okay, repair harness. If okay, repair control unit terminal poor contact or replace control unit.