What was found
STEERING INOP CAUTION MSG AFTER GEAR EXTENSION COMPLIED WITH QRH, MSG CLEARED, EXTENDED GEAR AGAIN, MSG REAPPEARED 1 MINUTE LATER. CONTINUED WITH QRH, TURNED OFF NWS AND LT IT OFF, MSG CLEARED (EMERGENCY DECLARED -- TRUCKS STANDING BY AS A PRECAUTION) TS AND INTERPRETED MDC CODES TO FLAG ELECTRO HYD SERVO VALVE, ECU AND HYD MANIFOLD. R & R ELECTRO HYD SERVO VALVE IAW AMM 32-51-15. R & R HYD MANIFOLD IAW AMM 32-51-15. OPS AND LEAK CHECK GOOD. ALSO CYCLED GEAR.