So I'm going up a hill one day, and the car didn't have any power. It felt like I was in 3rd, but it shoulda been in 2nd. Every once in a while, I wonder if the car'* in 3 or 4 (D or oD).
I had an idea, so I pulled out the manual, cause I needed to find out how the PCM tells the tranny what gear to be in. It'* as simple as two wires, providing the ground for two solenoids. Digitally, two wires can represent up to 4 combinations, in the tranny'* case: PRN1, 2, 3, and 4.
Decoding such a signal is easy, so I set out to modify the gear indicator (to the left of the shift) to show which gear was selected (as normal, PRND1234) and to display which gear the car was in (1234). Designing such a device is easy, but building, implementation, and modifing took a little longer.
ABOVE: 4 blue LED'* have been added (1, 2, D, and oD) to show which gear the PCM is requesting (coincidentally, what gear the car is usually in). The blue light showed up pretty well, as did the refelctions of the other 3 LED'* above it (left image), which cannot be seen otherwise, even during the day. The red selector light is hard to see, but it is still there (at the momment in Park). When the two lights converge, purple is seen.
To allow for color, the red tint was removed from the lenses of the gear indicator bubbles. Lukily, I had already replaced the bulb that lights these with a red LED months ago, therefore missing the red tint didn't matter.
ABOVE: This is the device doing the decoding. It recieves 5V, common/gnd, illumination que, and the 2 solenoid (A & B) inputs, borrowed from the PCM with a snap-on spitter. It outputs 4 signals for the LED'* and a common/gnd shared by all 4. It follows the schematic below pretty well, although I modified it later to follow the schematic exactly, and to accommodate external plugs for transitions/removal. Power, common, and illumination/dimmer input are borrowed from the harness located to the left of the shifter, which supplies the backlight and power to the gear indicator.
ABOVE: Location of modules (including a separate module for controlling a 5v source). At present, they sit in there pretty nicely, and aren't mounted.
Below is a how-to if you're handy with electronics. There is a lot left unsaid, but I figure if you can read the diagrams and understand them, there'* no reason to waste text explaining the obvious.
As with any electronic project, asses the design and test it before you implement it.