... just thought I'd post my findings ...
Being able to adjust PCM settings, I found a couple entries & tables concerning a shift light - something normally not found on any GM cars ... except for some Holden vehicles that have a stock shift light in their dash. Luckily, the function is available it seems for any LS1 motor, allowing for easy addition of a shift light w/o having to bother with buying some expensive electronics.
Anyway, after some ordeal finding the right terminal connectors for the PCM (the plug position for the shift light output is empty on a stock F-Body), the right part finally arrived and I went this morning and did the install.
The custom OS I have in my PCM also has a "valet switch" option, which can be used to limit speed or RPM or switch fuel injection tables (e.g. for nitrous), so I went ahead and added a second line at the same time ... will probably do the Valet switch config pretty soon, though I don't let anybody drive the car anyway if I can avoid it
Anyway ... back to the subject ... as posted on the other thread, I decided to put the lights in the air duct. Mainly as it's not obvious, but also I didn't want to mess up any part of the dash by putting any screws or holes in it. Anyway, removal of the air duct vents is a major PITA on a 4th gen bird, finally managed removing the one on the left after some 15 minutes or so.
Next up was putting the wires in. In order to get to the passenger area from the motor it was easiest using a hole already there ... in this case, a rubber grommet with a dozen or so wires can be found on the top half of the passenger side fender, problem is that the PCM is in the way for halfway decent access. And removal of the PCM isn't that easy, either, but manageable. Next I tried where I actually end up at with a stick. Afterwards, I used a wire the same way, allowing the cables to be pulled through from engine bay. Inserting the new terminals into the plug and putting the stuff back together is relatively easy, except for the PCM, which is even harder to fiddle back in than it was getting it out.
On the inside, pulling the cable through is quickly done if you release the glove box stops, letting it all the way down.
I used a small drill, barely larger than the cable (which is pretty thin) to put two holes into the air duct wall, then pulled the cable through from the rear. The shift light I built consists of 6 yellow LEDs, soldered onto a small piece of experimental printed circuit, plus a resistor to limit the voltage down a bit (the LEDs I used are running at 2V w/ 20mA). As the air duct is angled at about 45 degrees, I bent the LEDs by a bit more than 45 degrees, that way shining more in the direction of view. The circuit board is about 1cm wider on both sides of the LEDs, allowing for easy attaching of the board in the duct.
After soldering the cables (ground side towards the PCM, 12V feed to switched power) to the circuit, the LEDs lit up nicely when firing up the motor (the PCM had been set to activate the shiftlight at 1200RPM) ... After confirming proper function, two generous pieces of duct tape were used to stick the circuit inside the vent.
All in all, adding the shiftlight isn't a hard exercise, parts are somewhere in the $2 range, if you have the ability to configure your PCM ...
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