At power-on the displays show audit numbers (credit window "04", ball-in-play window "00") instead of the attract mode.

Game powers up in audit mode instead of attract mode

Cause: Battery-backed CMOS memory was lost: dead batteries, a damaged battery holder, a failed blocking diode D17, a bad 5101 RAM at IC19, or battery corrosion on the CPU board.

Checks

• Open the coin door (needed on System 6 and 7 for the memory protection switch).
• Switch the game off and straight back on, a few times if needed. If it reaches attract mode, IC19 is likely fine and the batteries or holder are the problem.
• If it keeps booting into audits with good batteries, the 5101 at IC19 is almost certainly bad.

Fix

• Replace the batteries or battery holder and check D17.
• If it still boots into audits, replace the 5101 RAM at IC19 and fit a socket.

Systems

• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Game keeps resetting: replace the 5101 RAM (an NVRAM works)
• Boots into audit mode every power-up with good batteries: bad 5101 RAM
• Game always powers up in audit mode: bad 5101 memory chip
• System 6 won't boot and fails the 5101 RAM test even after replacing it: bad 5101 stock
• Leon's test EPROM fitted but the LEDs do not start flashing
• Game powers up in audit mode
• Locks up when a second game is started: bad 5101 RAM
• "Adjust Failure" at power-on

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)