I have been having a number of intermittent electrical issues with my 2005 C6. They all happen together, seemingly at random and are not dependent on whether the car has been driven, i.e. you could go to it and find the problems described below, then come back later and find it behaving normally.

- the instrument cluster does not function or illuminate, with the exception of the engine light which briefly comes on as normal when the car is started.
- the DIC does not work either.
- the HUD works as normal.
- the controls for the HUD and DIC do not illuminate, however the ones for the HUD still work. Cannot confirm if the ones for the DIC still work as the DIC itself does not.
- the lights for the stereo controls appear to come on instead of the cluster dials, when opening the doors for example. When the car is locked they are the last thing to turn off, which isn't normal.
- the fuel cap and trunk release buttons function but do not illuminate.

It is almost like the power/signal that would normally activate the instrument cluster is being diverted to the stereo controls instead. I have had it suggested that this might be an issue with a ground connection. G201 was located, it was clean and tight. I'm not sure how to access G301 yet. These seem to be the only two that involve the instrument cluster.

The battery is less than a year old and healthy, the terminals are clean, the car starts every time with no other issues (at the moment!) and is driven regularly (at least once a week). To the best of my knowledge it has never been flooded. The connectors at the back of the cluster have been pulled out, cleaned and reinstalled with no effect, as have the connectors for the BCM in the passenger footwell. Basic OBD device shows no codes.

Based in the UK so no Chevrolet dealerships, there aren't many electricians even willing to have a look at the car where I live so looks like this will be a DIY job. Any suggestions or information appreciated.

 

Have you inspected / cleaned / replaced the 15A CLUSTR/HUD fuse at the BCM?

 

That fuse was the first thing I checked, it hadn't blown and seemed clean so ruled it out since that same fuse is apparently for the HUD too, which still works.

 

My experience here is limited, you’re going to want to ask Dano, but the HUD is controlled via the radio, and the DIC is on a different circuit. If you pull the radio, the HUD stops functioning, but the DIC functions fine.

 

Here's a couple of diagrams from the shop manual showing grounds G301 & & G302. Looks like they're located on the frame rails just behind the seats.
Hope this helps, good luck and let us know what the problem was when you find it.