The next step would be to check there is power at the fuse holder. If you've got a multimeter, remove the fuse and check you're getting ~12.5V at the fuse holder. This fuse way should be live with the ignition off as well as on because it also serves as the back-up for the odometer/clock.

If there is no voltage there, then the fault lies before the fuse box. If there is ~12.5V, then the fault is on the dash side, which should narrow things down.

A poor earth is next to try. The dash has its own earth to the battery as well as sharing that of the ECU.

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