The following is a description of installation of a CD head unit (Alpine CDE-7853) into the ’99 trooper S in replacement of the Isuzu cassette head unit (Delco). 

The plug in the trooper will need a wire harness to avoid cutting wires. The one I bought was a Metrawire ABMW-124 (also numbered 70-7712 for the rodeo).

Details of the head unit plug in the dash of the ’99 trooper S:

The plug on the trooper has the following wires feeding into it in two rows.  The top of the plug has the locking clip. R=red, G=green, O=orange, B=black, Y=yellow, W=white, and S designating a stripe. I determined speaker wires by matching to the speaker wire colors at the speakers. I determined hot wires by voltage measurement against car frame ground. I determined the ground by a resistance measurement. The connections from left to right on the plug, looking at the open part of the plug have the following wires attached:

Row 1: [Y (+ left rear spkr); O (+ right rear spkr); R&G-S (undetermined); O&G-S (ignition 12V); clip section, clip section; blank; W (+ front right spkr); gray (+front right spkr)]

Row 2: [Y&blue-S (- left rear spkr); B&O-S (- right rear spkr); B&G-S (car frame ground); G&R-S (undetermined); brown&R-S (undetermined); blank; R&W-S (battery 12V); R&W-S (- front left spkr); G&W-S (- front right spkr)]

The three undetermined wires were not necessary for the Alpine install. At least one of the unknowns likely supplies voltage when the lights are on to illuminate additional display items at night on the stock unit and should match the line on the Metro harness, but it was not tested.

Wiring the metro harness:

I was not satisfied with taking for granted that the harness was properly configured for the trooper. Based on my determination above, the Metro harness is properly configured for the trooper.

Follow the instructions for the wires on the Alpine and the wires on the harness. Almost all of these colors match.  I soldered each connection and put on wire caps. I also wire capped one unused wire on the harness for illumination. I taped the open side of the wire caps around the wire for each of the hot leads.

Physical installation process:

Remove the two top screws above the radio and the one near the lighter on the dash cover.

1. Remove the four screws on the shift console near the floor (two on each side).
2. Remove the 4WD HI/LO shift knob by unscrewing counterclockwise.
3. Lift upward on the console cover to provide room to remove the dash cover. The power and winter mode buttons are attached to the cover and have about 2-3” of wire. There is a clip that pops free in the top/back part of the console behind the power/winter buttons.
4. To pull the dash cover off, you will need to put the trooper in D or L with the key in the ignition.
5. The dash cover has two clips on each side that will release, by pushing slightly inward on each edge, while pulling the cover off. The lighter has a couple inches of wire and the cover can be tilted forward onto the gearshift lever.
6. Two screws (one on each side of the head unit) hold the vinyl dash on and need to be removed to access the head unit screws. Remove the head unit screws and pull out the head unit. Unplug the wiring harness and the antenna. (Watch that while removing the screws that the screws do not drop behind the dash cover—hard to retrieve them.) 
7. Note: when putting the screws back into the dash, the holes on the vinyl dash need to be realigned. The top right one is most difficult because there is also a tab that fits a hole there. Once the tab is popped out, that section of the dash needs to be pulled forward and to the left, so that the tab passes over a lip. Otherwise it will not pop back in the hole.
8. Take the brackets off the stock unit (2 screws on each) and put the brackets on the new Alpine.
9. On the Alpine head unit, take the two metal pieces on each side near the front face off. The screw on each side is very small, and I was lucky to get one out (used a little WD40 and tried later). These metal pieces are shown to be removed for Japanese vehicles and prevent the unit from fitting into the dash slot.
10. I shaved the corners of the dash cover cutout a little to make it squarer, because I was not sure that the Alpine head unit would come through enough. The fit is very snug. Aligning the unit, by a millimeter or so, in the cutout is time consuming and requires taking the head unit and dash screws out, taking off the brackets and tweaking them slightly, and putting everything back. Once it is square, the thin black faceplate on the Alpine snaps in place.
11. Put all the other screws back and enjoy the music.

Total install time: I would figure on at least 3 hours with the soldering.