Way back when fault codes first came out the F9 was saved for a door lock/latch issue on the self cleaning lock.
But today the F9 code from Whirlpool has changed.
A common trouble maker...
This code will most often indicate that the appliance is wired incorrectly at the home electrical supply, or at the hard wire connection. If your oven was installed recently (within approximately 3 months), contact a qualified electrician to verify the electrical supply.
During a power outage, if there was an unexpected amount of power supply line "noise" that the control detected as an incorrect voltage amount, the control could display the F9, F9 E0 or PF Error Code. Also, if any keys were pressed before the 10 second delay interval on power up, this could cause the F9, F9 E0 or PF to appear.
1)~Power unit down by turning off the circuit breaker(s) for one (1) minute.
2)~Power unit up by turning on the circuit breaker(s).
3)~Monitor the oven for one (1) minute to ensure the error code does not display again.
4)~Verify oven operation.
A copy of the reference model# and code displayed on the clock assembly.
F9 Whirlpool range - CLICK HERE TO VIEW - Pictures compliments of ApplianceAid.com