C5 owners are very familiar with the annoying “Twilight Sentinel” feature that automatically pops the headlights up in low light situations, such as driving through a tunnel or entering/leaving your garage. '98-up models have the luxury of disabling this feature through the DIC or by pulling a fuse or relay, but this is not possible for the '97 model year. For this year, on Canadian models only, the DIC function was disabled at the BCM by the factory for reasons known only to Transport Canada and the patron saint of Corvettes. However, I've done a fair bit of research on this issue and have come up with three options to bypass this issue, as follows;
1 - By far the easiest and cheapest option is to lift the emergency brake lever up one click before starting the car. If you've ever been to a drive-in theatre within the last 15yrs or so you'll know that this disables the DRL's so that the ignition can be turned on to allow the movie soundtrack to be played through the car stereo. On the '97 C5 this will also disable the Twilight Sentinel and the headlights will stay in the down position. The downsides to this method are that it must be done every time you start the car and the park brake must be lowered once you're in the daylight or you'll have a warning light on the dash and the possibility of a ticket for motoring about without your DRL's lit up.
2 – If you can find a GM dealer willing to work on “old” cars, you can get them to unlock the DIC by using a Tech II diagnostic tool to cancel the BCM input. Then you just switch off the system via the DIC. The downsides, apart from finding a GM dealer willing to do the work, is that you will likely need to pay for this and even then only if you can convince them that this is not considered to be “disabling a safety feature”.
3 – You can remove the defroster vent on the dash, unplug the light sensor and stuff a 4.7K OHM .25W resistor in it's place to trick the system into thinking there is sufficient light not to activate the headlights. It's a bit tricky to do because of the limited working space and you need to be very careful not to drop the connector down into the dash while you're mucking about in there, because a full dash disassemble is the only way to get it back.
Hopefully this info will help other new C5 owners like me and they won't have to spend hours wading through the interweb like I did to come up with the fix.
1 - By far the easiest and cheapest option is to lift the emergency brake lever up one click before starting the car. If you've ever been to a drive-in theatre within the last 15yrs or so you'll know that this disables the DRL's so that the ignition can be turned on to allow the movie soundtrack to be played through the car stereo. On the '97 C5 this will also disable the Twilight Sentinel and the headlights will stay in the down position. The downsides to this method are that it must be done every time you start the car and the park brake must be lowered once you're in the daylight or you'll have a warning light on the dash and the possibility of a ticket for motoring about without your DRL's lit up.
2 – If you can find a GM dealer willing to work on “old” cars, you can get them to unlock the DIC by using a Tech II diagnostic tool to cancel the BCM input. Then you just switch off the system via the DIC. The downsides, apart from finding a GM dealer willing to do the work, is that you will likely need to pay for this and even then only if you can convince them that this is not considered to be “disabling a safety feature”.
3 – You can remove the defroster vent on the dash, unplug the light sensor and stuff a 4.7K OHM .25W resistor in it's place to trick the system into thinking there is sufficient light not to activate the headlights. It's a bit tricky to do because of the limited working space and you need to be very careful not to drop the connector down into the dash while you're mucking about in there, because a full dash disassemble is the only way to get it back.
Hopefully this info will help other new C5 owners like me and they won't have to spend hours wading through the interweb like I did to come up with the fix.