KNOWLEDGEBASE

1. The ErrP (PF, E- P, E-P in some older models) comes from a reset of the processor during a firing. Things that can cause a reset are power loss, shorted relay coil, or electrical noise on the microprocessor circuit.
2. The shorted relay coil is easy. Every time the controller tries to turn on the relay the display will go blank.
3. A pilot relay setup (like in a DaVinci or Easy-Load panel) is usually the only time we have a noise issue. The cure includes a MOV across the contacts of the pilot relay (we do as standard). Moving wires away from the back of the controller and making sure the low Voltage wires and TC wires are not woven with the power wires is also important. See this link for more information on electrical noise.
4. The power loss is a little trickier since it is usually intermittent. It could be a bad circuit breaker, a bad connection, a bad fuse holder or a transformer issue - anything that interrupts power to the control. For instance, a transformer that has a broken wire at one of the terminals could cause this (making contact most of the time but heat or vibration would open the connection). 99% of the time it is a faulty circuit breaker and the circuit breaker needs to be replaced. 
5. What do you do if this happens while you are firing?
6. Try running a new program and just see if the control works. Seeing a PF could just mean that you had a power failure but all is OK now.

Things to Check

1. Check Power Cord
2. Check Power Relay
3. Check the transformer for proper operation
4. Check Wires and Wire Connections
5. Check Your Voltage
6. Run a Paper Test
7. Troubleshoot an INF infinite input switch (older Manual Kilns)