Code B1006 will be displayed when line accessory voltage is greater than 16.0 Volts for more than 10 seconds.
This is telling that your instruments are geting to much
voltage should be 11.6V-13.8V
i would check the voltage regulator probably it is faulty, check also the Battery ground cable !
According to the Electrical Diagnostics manual
The codes you mention come under the issues of "Accessory or Ignition Line Overvoltage"
Furthermore, Ignition and accessory voltage is constantly monitored by the speedometer (terminal 1 ignition and terminal 6 accessory). If
the battery voltage fails to meet normal operating parameters, a DTC is set.
• DTC B1006 is displayed when accessory line voltage is greater than 16.0 volts for longer than 5 seconds.
• DTC B1007 is displayed when ignition line voltage is greater than 16.0 volts for longer than 5 seconds.
As others have mentioned the fuse and relays need to be check/cleaned and coated with dielectric grease.
I would also add the following connections to clean and grease with dielectric grease:
1) Speedometer and Tachometer connections
2) Voltage Regulator Connections

Brad