Ran a search, but I couldn't find anything on my specific issue going back a few pages in the results, so here we go.

I turned the Twilight feature on the other day, as my past two vehicles have had similar auto-headlight features and I didn't want to have to expend the effort to flip that switch every time (epitome of laziness).

It was working fine until last night, when I was driving home at dusk and the headlights didn't come on when I expected them to. Flipped the headlight switch, nothing happened; lights didn't flip up or anything. Scrolled thru the features on my DIC, turned twilight off, tried again. Still nothing.

Drove home while flipping the switch (lo beams, hi beams, on, off, parking, all over the place) every couple minutes to see if they'd come on, but nothing happened. My fogs are able to turn on when the headlight switch is on, though.

Headlights refused to function on the way to work this morning as well.

Anyone have a schematic on this system, and a general direction for me to look on troubleshooting?

 

Were the lamps on but not raised?

 

Check minifuse #6 in the passenger footwell fuse box.

 

Great question. I have no idea. I will check this when my wife gets home with the car in about half an hour...

 

Will do.

 

There are really only three items for the headlamps. Headlamps themselves, headlight/multi-function switch and lastly the headlamp controller. As lucky suggested, fuses first as they are easy!

 

Fuse 6 is good, 0 ohms. Headlights are NOT turning on. Manually opened the RH light, it didn't come on or go down again on its own.

Where do I check for power to ensure my switch is contacting the ON contacts and not just the parking light contacts? Also, if it was the switch, wouldn't twilight still work?

 

Only code I have is A1-RDCM B2265 H, which I believe to be entirely unrelated.

 

Okay, I take it all back. The Twilight feature DOES work; it just must not have been dark enough out to turn them on last couple tries. When I try to open the lights via the switch, I get nothing.

How much is a new switch? I have a 50/50 warranty with the stealership that I bought the car from for another couple weeks, but I am also fairly handy with a wrench (and a soldering iron) if its a fairly simple install. I would rather do the work myself than let any dealer touch it....

 

Yes, sounds like the headlamp switch which has a fairly high failure rate in the C-5's. I suggest contacting Gene Culley at www.gmpartshouse.com

 

So, just to reuse an existing thread instead of starting another, anyone have any idea what A1-RDCM B2265 is all about?

 

B2265 Horizontal Position Sensor Fault

I have no idea and no C-5 manuals to look it up. Taking a wild guess here, the window isn't set right or similar having to do with the position. Sorry, no clue

 

DTC B2262-B2265
Circuit Description
The driver door module (DDM) and the passenger door module (PDM) receive mirror position signals from the mirror horizontal and vertical position sensors. These signals are used by the door modules for memory recall functions of the driver and passenger mirrors. The door modules command the mirror memory settings based upon the voltage level received back from the position sensors. Each door module provides a 5 volt supply, a signal and a ground circuit for each of the position sensors. The horizontal and vertical position sensors are variable resistors that the door modules monitor voltage levels across. When a memory setting is recalled, the door modules command the mirror motors in the appropriate directions until the stored position sensor voltage levels are achieved. The DDM and PDM monitor the signal circuits to determine if the voltage level is out of range. If the DDM or PDM detects a voltage level out of range for greater than 2 seconds, a DTC is set.

Conditions for Setting the DTC
The DDM or PDM detects a mirror position sensor signal voltage range under 0.1 volts or over 4.78 volts.
Condition must be present for greater than 2 seconds.
Action Taken When the DTC Sets
Stores a history DTC B2262, B2263, B2264 or B2265 in the DDM or PDM memory.
These DTCs can only be set as a history code even if the malfunction is current.
No driver warning message will be displayed for this DTC.
Conditions for Clearing the DTC
The DDM or PDM detects the correct mirror horizontal and vertical position sensor signal voltage range (0.1-4.78 volts) for longer than 2 seconds, and:
The DTC is cleared using the IPC clearing feature, or
The DTC is cleared using a scan tool.
Diagnostic Aids
An intermittent malfunction may be caused by an intermittent open or short to ground in a mirror signal circuit.
If the DTC does not reset after the code is cleared, then the problem may be intermittent. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.

 

Lots of good info there. I am guessing my first step in troubleshooting that would be to move the RH mirror in a few different directions and see if it allows the code to clear? I have reset the code a few times but it always pops back up instantly.

If moving the mirror around to unstick the voltage issue doesn't work, where do I go?