As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT 2933, LT PROP RPM INDICATION ERRATIC. INDICATION VARIES FROM ACTUAL RPM AND ZERO INTERMITTENTLY. AIR TURNBACK TO MSP. MAINTENANCE REMOVED AND REPLACED LT PROP INDICATOR P/N 522742, S/N ON 0387128, S/N OFF 9802872 IAW AMM 61-40-05-2. OPS CHECK GOOD.