[Thumper]

It may be necessary to dump residual capacitance in the system that stores the codes to get rid of them. This is often done with a reset button that grounds the circuit in a device, but... A simple wasy of doing this is to disconnect the battery and connect the positive and negative wires together and allow any capacitance to drain (takes seconds). Then turn the key on with the wires still connected in case the codes are safe from discharge with the key turned off.

Keep in mind the battery is out of the loop here. We are not talking about connecting the two poles of your battery!

Lots of devices in cars can maintain codes and programming with tiny amounts of residual charge held in capacitors inside components. I learned this when I found out that I could fix my windows or door locks in my car by doing this. When you reconnect the battery, the default programs/settings are loaded from EPROM chips in the components. Pretty cool.