Hi Kenny, below is a summary of the Fluke 165xB series MFT error codes:
Error 1, Self-Test failure. Return tester to Fluke service centre.
Error 2, Over-Temperature. Wait let tester cool down.
Error 3, Internal protection failure? Return tester to Fluke service centre.
Error 4, Fault Voltage. Check the installation, in particular, the voltage between N and E.
Error 5, Excessive Noise. Loop, RCD tests, switch off all appliances. Earth Resistance tests, move earth stakes.
Error 6, Excessive Probe Resistance. Put the stakes deeper into the soil. Tamp down the soil directly around the stakes. Pour water around the stakes but not at the earth electrode under test.
Fuse, Fuse in battery box is faulty.