In switch test every switch on the white-yellow row shows up as the matching switch on the white-green row (for example trough 2 reads as trough 3, so the game kicks two balls). Unplugging the white-green row at the CPU makes them read correctly.

A whole switch row reads as the next row: fault in the row wire harness

Cause: A fault in the playfield harness for that row, such as a bad crimp or solder splash, was tying the two rows together. The CPU and switch diodes tested good.

Checks

• Test the diodes on the affected rows with one leg lifted.
• Unplug one row at the CPU at a time to see which rows interact.
• Disconnect the coin door to rule out its switches.

Fix

• Run a new row wire from the CPU connector (1J10 here) to each switch on the row, adding them one at a time and testing as you go, then tidy the new wiring.

Systems

• Williams System 11C

Games

• Jokerz!

Related tips

• Lane change not working on Taxi and later System 11 games
• A whole switch row or column is dead
• How wiring faults show up in switch test
• Matrix fault remains with a good CPU board
• Row or column error: CPU board or playfield?
• Fixing a dead switch row on the CPU board
• Strange behaviour across a whole row or column from a switch diode
• Random switch closures, random tilts or slam from bad resistor networks

Source: Pinball Repair help group!! (Facebook group)