What was found
BOTH FMC P/RST LIGHTS KEEPS ILLUMINATING ON DESCENT. WHEN YOU RESET IT, IT KEEPS COMMING BACK ON. NO SCRATCH PAD MESSAGES ASSOCIATED WITH IT. THE FMC'S STILL WORKED FINE. GROUNDED - YES. VERIFIED DISCREPANCY. ACCOMPLISHED FMC #1 AND FMC #2 BITE TEST B737-900 FIM 34-61 TASK 801. DID NOT FIND FAULTS RELATED FAULT. INSPECTED MCDU INFLT FAULTS. FOUND SEVERAL LEFT FMC FAULTS. DUE TO HISTORY - REPLACED LEFT FMC COMP. OPENED/TAGGED 2 CBS. RMVD AND INSTALLED NEW LEFT FMC. RMVD TAGS/CLOSED 2CBS. REF B737-900 AMM 34-61-02/401. ACCOMPLISHED LEFT FMC COMP INSTALL TEST REF STEP E OF B737-900 AMM 34-61-02. SYS CKS NML. ALL SW LOADED AND VERIFIED REF B737-900 AMM 34-61-00/201.