For the people who are relatively electronically inclined and have access to a good soldering station here are the step by step instructions how to add a hard wired AUX input to your
OEM base ’96 and up sound system:
1. You need to remove the HU (or some may refer it as stereo). There are plenty of post about how to remove the stereo (
see here how)
2. You need to remove the top and the bottom covers of the HU case:
3. Rest the HU on the up right position and remove the tape module by disconnecting the 2 connectors and removing the 3 screws shown in the picture bellow
4. Remove the volume knob (stereo in OFF position) by pulling the knob straight out then unscrew the nut behind the volume knob:
5. Remove the fort fascia of the HU by carefully releasing the 6 (2 on top and 2 on each side) very fragile clips. Use small shims to hold the clips unhooked, when all 6 have shims pull the top side of the fascia out just enough so the clips are half way out then turn the HU upside-down and observe the other 2 clips that need to release by pressing in. Once released carefully pull the fascia out (comes out with buttons and all).
6. It is recommended to remove the front fascia metal backing to get better access to the audio processor. This is done by removing the 4 screws (2 on each side) and the one single screw on the bottom of the main PCB (on the passenger side of the HU visible with the HU upside-down and bottom cover removed – can not be missed). Then is a matter of disconnecting the Volume/ON-OFF connector from the HU main PCB end and releasing the front PCB controls connector witch disconnects from the front fascia when removed but remains attached to the metal backing plate due to the plastic sleeve.
7. At this point you have plenty of space to access the audio processor. Notice on the driver’s side of the HU a heat sink with 2 chips attached, those are the final amplifiers. On the middle of the plate is a large metal cover and on the drivers side is another PCB with a metal cover (this vertical PCB is the Radio module). Now that you are familiarized with the mother board, looking to the HU (or what ever remained of it) as you are in the diver seat on the area between the big metal cover in the center of the board and the heat sink with the final amplifiers locate a square 32 pins chip with 8 pins on each side. See the picture below in the top right medallion is a view of the mother board and the chip is highlighted with a yellow circle.
8. Follow EXACTLY the diagram above to connect the jack connector to the sound processor. In the top side of the diagram you have a very accurate representation of the components around the sound processor chip so you can easily identify the points where you need to attach the wires to the jack connector (again I can NOT express enough how important is to connect exactly as I indicated in the image or your HU will stop working completely – no more sound!). The red tracts labeled Left/Right channels are the audio tracts. VERY IMPORTANT look carefully where the red wires connect to the audio processor area. Notice the YELLOW conductive tracts are? You need to carefully cut them off scratching the PCB with the tip of a stronger needle. Be very careful so the needle does not damage anything else and also verify there is no more contact once the conduit tract was cut. Verify with the ohmmeter to find a GND connection point for the GND pin of the jack connector. A GND point is any point that measure 1 ohm or less from the HU cover or the large metal cover on the center of the PCB (hint, see were the cover is soldered on the PCB).
9. This step is optional: on the bottom side of the image you will surely recognize the HU display. Notice the green lines? If you connect wires as indicated (with the green lines) then you have the convenience of turning ON the WX logo on the screen every time the AUX connector jack is in. Just match the display pins with the ones shown in my diagram.
10. I would strongly recommend to locate the jack connector on the front fascia on the right side of the tape EJECT button (see the picture in my previous posts). It is the perfect spot to locate the jack connector (is like it was designed for this). First remove the PCB from the fascia (is a matter of 8 easily accessible screws) so you can see the back of the plastic face where the jack will be located. You will need to drill a hole in the fascia (measure 10 times drill once). Start with a small M3 drill bit then gradually increase the diameter until the hole is just large enough so the jack ring fit snugly (some inside trimming of the plastic fascia is required to bring the ring flush with the outer surface). The Jack connector is about 2 mm larger than the space behind the plastic fascia so you need to cut a small port in the front PCB directly behind the location of the jack connector (again measure 10 times cut once). If you look at the PCB there is no circuit in that area is just a blank area (shielded). Then jack connector is to be mounted on a PCB cut to exactly the same dimensions as the pin area of the jack connector and my recommendation is to solder this small PCB on the front PCB. Make sure is flush with the front PCB so you can mount the fascia back on the metal backing.
Use 26 AWG wires for all connections and try to keep the wires no longer than 15 inches. It is important to use the IDENTICAL jack connector shown in the diagram. Should you not be able to find one then locate one that has at least 5 pins (one GND and 4 – 2 per channel). Using a ohmmeter identify the pin on each channel that has continuity to the jack male connector corresponding channel (when inserted). That pin is connected to the capacitor side and the other one connects to the chip output. Here is the chip pin description (in the same position as in the diagram above):
Please note the chip is covered with a layer of silicon. You will have to carefully clean up the silicon using a small blade or a needle.
DO NOT attempt this unless you are SUPER confident in your electronics abilities or you can permanently damage the HU.