I'm aware there are many electrical gremlins on a C5. This is a new one, at least for me;
Couple years back I had a new (not a "re-man") B.C.M. installed on my 2000 C5. Long-VERY long-Story short: When I turn on my lights using headlight switch, the headlights open and both head and tail lights light, but there are no dash lights. When I go to the DIC and press "options", and go to "twilight sentinel" to activate twilight sentinel everything on the DIC goes black, but headlights open and both head and tail lights light, but still no dashlights!!!! Also all additional options on DIC are no longer available, as the DIC remains blacked out when twilight is turned on. Pushing options again does nothing-DIC remains dark. Anyone have this happen before? It is VERY aggravating. All fuses under the hood check out good by voltmeter. PLEASE HELP!!!!

 

did you check the dimmer for the dash lights and see if they're turned off?

 

Just the gauge cluster or all lights (HVAC, radio, doors etc)?

If it's the former then it might be a cluster issue. If it's the latter then this:

 

Yes, it's not the dimmer. That would make all DIC options disappear when activating twilight sentinel? All lights working EXCEEPT dash lights......

 

Update: I have checked the tail lights, and they also do not work. I had a new 4 way flasher installed, and it works fine. Also checked #6 fuse in passenger footwell (ONLY G.M. would put a fuseblock in this location!!!) and voltmeter says it is good.....

 

Might as well mention the "BUTCHER" that did the 4 way install broke my ashtray door pivot point on drivers side, and broke plastic oval "ring" that circles the A4 shifter. Butcher is well known engine builder in Wixom Michigan that I would avoid at all costs

 

UPDATE-Thanks to all for your input. Reason I dont think its multi/4way switch is it was replaced only 3,000 miles ago, because the the turn signals wouldn't work anymore unless I pushed the old one in and out a few times. THE UPDATE:
I cleared many codes with the "options/fuel switch onboard diagnostics. The DIC no longer goes black when I enable twilight sentinel. The headlight low beams do not work-BUT-Years ago I bought a relay from Mid America Motorworks-MAMO-That allowed me to run all 4 headlights when on Hi Beam. On Hi Beam, the low beam lights come on!!! But NOT when turned on to the specific low beam position on the headlight/cruise/turn signal switch!!! Still no dash lights (they do loght when turning dimmer all the way bright with key in ignition, but not when engine running and headlights on!!!! Checked tail light bulbs with voltmeter, and the bulbs are all good!!! But-They will not work even with all 4 headlights lit. Checked #6 fuse under footwell, and it is O.K.. Starting to lean towards headlight/turn signal switch, but shooting in the dark. This thing really has me going in circles!!!!!!!

 

UPDATE (another one!)
I ran a code check, via holding options button/while pressing fuel 4 times, and came up with following, even though I don't know how/what effect they would have on tail/dash/low beam on headlights problems Im having:
TCS 1283 H (even though H denotes a "History" code, it reappears every time I clear it).
BCM B 2583 H (another "H" that also reappears as soon as it is cleared).
SCM B 2605 H (3rd H that reappears when cleared).
Must the TCS (traction control system), BCM (body control module), and SCM (steering control module) codes all be cleared/set with Tech II only? Because resetting them with DIC option/fuel code clear does not seem to clear it up. Thanks to all......

 

ttt-Anyone?

 

No low beam is a problem with the dimmer switch or both fuses for each low beam bulb or a wiring issue.

None of the codes would affect the cluster lights.

They can be cleared using the DIC.

 

Another update. Found problem with Low beams: Melted wire! Repaired and all is well with Low beams now. Also found out BCM was never fully programmed!!! Had a dealer do that, and made a huge difference. Now have both high and low beam headlights, tail lights, and dash lights when using twilight sentinel-BUT-If I deactivate the Twilight S. in the D.I.C., and use headlight switch for head and tail lighfs, I have high and low beam, but STILL NO TAIL LIGHTS!!!!! I've made progress, but how can tail lights be functional when using twilight sentinel, but wont come on with head light switch????

 

 

I'm currently experiencing a similiar problem with no gauge lights, but my taillights and rear signals all work. Gauges, warning lights, and dimmer all work just no gauge or needle lights. Any thoughts?

 

I know anything is possible. The MFS switch is only a little over 3 years old with less than 4,000 miles on it. The headlight switch is original (18+ years old/90,000 miles), and I wonder if this could be the problem. Maybe activating the headlights but not the tail lights? Is this switch easier to change than the MFS?

 

BTW..... All the gauges and the dash lights are all working fine now.....

 

The headlight switch is part of the MFS stalk...

 

Thx for the info. Really dont know if any other automakers do stupid $%#@ like this, but what sense does it make to put a wear item like a MFS in a position you must pull a steering column to R&R it, but leave it to G.M. to be one of them for certain. These guys can't be wondering why they filed bankruptcy, can they? I mean, a steering column that locks up for no good reason, a supercar like the 427 Z06 that drops valves, and stupid @#$% like this, and they wonder WHY? REALLY? I guess while I'm at it, you can include the no longer produced EBCM, the SWPS that is no longer available, the BCM that is no longer available, etc., etc.. I digress....

 

Since when????

 

Dealer said this. Also other forum members say it's a Hell of a job. Which was my point: Why make something so damn difficult to access/repair? If you have an easy way to do this, I would be most grateful......

 

The factory manual says to remove the steering wheel, the knee booster cover, the upper and lower column covers, disconnect the wires and then 2 bolts to remove the switch. I have no idea if you can shortcut around the steering wheel removal or not. It doesn't require pulling the column.