As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT PROP NP INDICATION WENT TO ZERO WHEN PROPS WENT TO MAX ON FINAL. AFTER LANDING IT WENT BACK TO NORMAL. MAINTENANCE COULD NOT DUPLICATE PROBLEM. UPON INSPECTION OFF LEFT ENGINE YELLOW HARNESS FOUND CONNECTOR TO DECU EXTREMELY LOOSE AND CONNECTOR TO NP SENSOR ALSO LOOSE. TIGHTENED CANNON PLUGS. OPS CHECK OK.