Paging Dr. Steveskyhawk for Cassette Bypass Surgery

[Guest steakneggs]

I've been trying to find someone who has done the input jack thing on a 88-89 that will "fool" the CRT into thinking that the cassette is still there. It needs to have a signal from the deck that lets the radio know that it (the deck) is running so that the radio will shut down but the volume arrows will still function. The signal goes through a "data line". I was wondering if a toggle switch could be hooked up between the red wire (hot) and the data line that could be switched on to perform this task or is the data something other than 12 volts. I also don't know which wire is what because it doesn't match my manual. Hep. Steak

[Guest steveskyhawk]

Steak

I got my information from this forum and the service manual. Unfortunatly my work was done on a 91 which is different than yours. As you know some 90-91 models had a CD player. Mine didnt. I got the wiring I needed from Jim Finn and a switch from radio shack and "faked" the radio into accepting the audio from my mp3 player. I turn on the switch and the radio accepts the audio that would normally be coming from a CD player. Never drilled a hole or cut original wiring. Switch is inside the doghouse. It works nice and no preamp was needed. The MP3 player is insde an Alpine navigator which fades out the music when it gives a navigation command in female voice of course.

Sorry I can't help more. You will get it.

[Guest steakneggs]

Thanx. You wouldn't happen to know which wires the switch was hooked to, would you? P.S.-I get commands in a female voice all the time. Steak

[Guest steveskyhawk]

Sorry Steak, I dont have any info on an 88-89. At least the female voice from the navigator never says "i need to go to the bathroom".

[Guest TommyH]

http://cardomain.com/ride/2467533/3

I did it there.

[Guest steakneggs]

Thanx TommyH but I couldn't tell from the pics which wire gets soldered to what. Steak

[Guest TommyH]

I honestly just messed around with it until I got a sound that sounded correct.

[Guest campolojr]

ont the white clip from left to right black,red,white green wire is red thought and that is with the clip up if you take of the hood of cassette i shows what the wire colors are

[Guest William Vernon]

Huh? I wish someone could provide a clear explaination of how to fool the radio to accept the aux input. I tried messing around with it and could never get it to switch over. I've searched the interwebs and I don't think anyone has provided an answer yet.

[Ronnie]

This link to Tommy's webpage seems to explain how to do it and has photos. Is that not what you are wanting?

[DAVES89]

From what was explained to me is this;

You take the front trim panel off at the cassette deck. Remove the 4 screws that are holding the cassette deck in place. Remove cassette deck and hold in your hands. Turn key to the on position. Push radio hard key, press play. Disconnect cassette deck lead. Plug lead into your new unit[wires should be reconfigured to match up to what you want] Your computer should now be fooled into thinking that it is running the cassette deck and will always run your auxillary unit unless the memory is lost by disconnecting the battery.

What you may want to do is get yourself another cassette deck and take out the wiring harness that is in the cassette deck and wire that end into your auxillary unit. This way if the memory is lost, you can simply reconnect the original cassette deck, then do the above steps to trick the computer as often as you need to.

Or you can do what I did, which was to mount my GPS unit in the cassette face and use that instead. I get more use out of it and it looks great and modernizes the car to new technology.

[Guest steakneggs]

The problem is that if I use a portable unit (CD, MP3 or IPod) it HAS no power lead because it runs on batteries. I am beginning to believe that it must be powered by the vehicle electrical system to fool the CRT. I cannot even get the tape screen with the wiring disconnected. I could possibly connect the power wire to a separate cig lighter socket to run the portable unit. Trying to avoid wiring running everywhere. Steak

[Guest TommyH]

What are you talking about, steak?

You just plug the larger connector into the cassette player, load a cassette, push play on the radio, push stop on the radio, then disconnect the cassette player. Then all you need to do after having the aux input wired up, is to plug your music device in, and push play on the radio. It is so easy.

[Guest steakneggs]

I'll try that method. But I still don't know which wires get spliced to what. I can't tell from the pics. I'm going to get an aux pigtail today from Radio Shack so I'll be ready to splice when that info surfaces. Steak

[Guest William Vernon]

What if your cassette player doesn't work?

[DAVES89]

Doesn't matter. The cassette is what is called a "slave" componet and does not have the capability to communicate back that it doesn't work.

[Guest William Vernon]

If I push play with the cassette player plugged in, nothing happens. The radio is not fooled into playing the (broken) tape player. This has been the issue with me all along, I can't fool the radio into switching over.

[DAVES89]

You must have a tape in the tape deck. Press play. Then you can disconnect the tape player and plug in your new unit.

[Guest William Vernon]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DAVES89</div><div class="ubbcode-body">You must have a tape in the tape deck. Press play. Then you can disconnect the tape player and plug in your new unit. </div></div>

That was the key. I was trying to use a cassette adapter and pushing play wouldn't respond. Dug out an old tape and away it went. Thanks for all the help guys

[Guest TommyH]

I think this calls for an instructional video.

[Guest William Vernon]

FWIW, it doesn't sound so good, kinda muddy compared to my in-line FM modulator setup. I would have expected it to sound better, oh well.

[Guest steakneggs]

Apparently if it energizes but just won't play due to a broken belt the above method will work. I have to push down on the wheels just to get a tape into mine. But I was able to make the tape screen appear, which is necessary to run aux equip. I don't like the above method because I would rather cut the harness and solder the pigtail. And I don't want to go through the temp hookup ritual after I've disconnected the batt for some reason. Steak

[Guest TommyH]

We are looking for a better way. But that would require knowing the programming langueage used by the BCM and radio, which we don't. Yet.

[Guest William Vernon]

A correction to the wire colors described on your page (Tommy) - green is right positive, grey is left positive, black is ground (bare wire useless for aux setup). That is why my Ipod sounded muddy at first, it was incorrectly wired.

[DAVES89]

William,

Could you list all the wires colors and uses? I am sure Ronnie could use this for his website. I am also thinking about wiring one up as well as I have an extra cassette deck and I can take the interior harness out and wire to that.

[Ronnie]

After looking over the relevant section of the FSM concerning the data line, it appears no coding is required to make changes that accomplish what this thread is talking about. The data that is transfered to the BCM appears to be in the form of resistance and/or voltage values. I am guessing that a cumulative voltage or resistance is used by the BCM to determine what components are present in the system.

I don't have time to dig into the workings of the system. If someone here with some electronic (not necessarily programming) skills would look over the photo I have provided I'm sure they could come up with a solution to doing away permanently with the Cassette player.

[Guest William Vernon]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DAVES89</div><div class="ubbcode-body">William,

Could you list all the wires colors and uses? I am sure Ronnie could use this for his website. I am also thinking about wiring one up as well as I have an extra cassette deck and I can take the interior harness out and wire to that. </div></div>

There are only 4 wires on the small harness and I think my last post describes their use, Dave. Other than that, it works exactly as described by your and everyone elses posts.

[Guest TommyH]

I do remember that the 88 and 89 have a slightly different wiring. THe 88 only has three wires I belive. That is where I got my practice harness to work on.

[Vincent Vega]

The 88 does indeed only have 3 wires.

Black = Ground

Grn/Wht = Right

Brn/Wht = Left

I did a quicky job last night using the splice type connectors. (no wire cutting) It works, but not very well. I get interference when I adjust the volume. My Ipod needed full volume and it sounded muddy. I'll try again some time with better wire and a more solid connection.

[KDirk]

I thought I would add a couple of things here:

The wiring Vincent Vega describes above is strictly the audio path between the outboard cassette deck and the RIM (radio interface module). The controls for the tape deck (play, pause, ff/rew etc.) are all handled as packet level messages on the vehicle data bus. Or, more specifically the E&C (entertainment and comfort data line) bus which operates somewhat separately from the ECM/BCM data line.

Since these messages are generated and received in the electronics based on input on the touchscreen, there is no easy way to emulate them to "fool" the system without the cassette player present, at least every so often as in after a battery disconnect.

A microcontroller could be rigged to do this and supply the anticipated response to the CRTC and/or RIM but this would be a fairly involved solution requiring skill and cost.

I think the easier solution might be to take the electronics off the tape deck (removing the mechanical portion) and stuffing it out of the way, but keeping it connected. This still would require some electronics expertise as the cassette deck has a sensor switch that detects the presence of a cassette. This switch would have to be "jumped" into the closed position.

This would fool the RIM and CRTC into finding the deck present on the bus, and then the audio from whatever outboard device you choose could be fed into the 3/4 wire audio harness as already covered. Then, the opening for the cassette deck could be made into a storage pocket for an ipod or similar device, or a custom trim could be made for a nav/satellite radio/car pc setup.

As an aside, I do not know enough about this particular deck to know if it can detect tape "tension" and will auto stop if it thinks the tape is broken or missing. Many cassette decks do this to prevent the tape from getting all wound up in the capstan rollers as a safety feature. If this is the case, then my idea above may still not work.

KDirk

[Ronnie]

Kevin, would you please take a look at the photo and comments in my previous post? It is from the FSM and is a diagram of the data lines between the cassette, radio, and the CRTC. The CRTC then sends data on to the BCM for processing. It appears from looking at the diagram there are resistors inside the cassette that play a part in telling the CRTC the state of the cassette player. It seems that it may be possible to simulate the resisters inside the cassette some way to 'fool' the CRTC and BCM. I'm probably wrong but I would like to hear your comments.

Be sure to expand the photo to full size to see it in detail.

[Guest William Vernon]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TommyH</div><div class="ubbcode-body">I do remember that the 88 and 89 have a slightly different wiring. THe 88 only has three wires I belive. That is where I got my practice harness to work on. </div></div>

Oh okay, cool. My car is an 89.

[KDirk]

Ronnie,

On closer examination, I see in the FSM Diagram that the modules are illustrated as having the schematic symbol for resistors inside (withing the shaded portion). I can see where this would lead one to believe that a variable resistance was being employed as a signal encoding means.

In fact, this approach is used with a lot of older wired remotes for audio/video equipment. In this type of setup each different button has it's own unique resistance value, coded for the equipment to understand what button was pressed.

Many GM steering wheel controls used this type of system (including the Eldo/Seville/Deville from 96-99). The varying resistance was then processed by an A to D converter and converted to discrete switch outputs in a module where it was communicated as a command onto the vehicle data bus.

Regrettably, this is not the way the 88/89 Reatta radio/cassette system works. I'm not sure why they are showing resistor symbols in the module outline on the diagram (perhaps just to show the device is solid state electronics in a very simple form or that it represents a resistive load) but these symbols aren't representative of actual resistors in this case. Not that there aren't actual resistors within the module, as there certainly will be anytime there are electronics preset. Just that the resistors aren't serving as an function encoding means.

If you look at the diagnostics section of the FSM, you will see a TECH 1 tool can be used to simulate the various functions of the radio and cassette. It can do this because it is generating the same E&C messages that the components expect to see when they are "talking" to each other in normal operation.

In other words, from the TECH 1, you can send, for example, a cassette "play" command and the cassette will start playing provided it is present and functioning correctly. This is done by way of a cartridge (ROM) installed in the TECH 1 that has the E&C commands for the particular car line(s) and year(s) that contain the needed protocol to communicate with the set of devices under test.

I hope all of this makes sense.

KDirk

[Guest steakneggs]

We are getting closer to the answer I'm looking for. Steak

[Ronnie]

Yes, it does make sense. I just wanted to be sure we weren't overlooking something that may have been simpler to implement.

Like they say... There are 10 types of people in this world: Those who understand binary and those who don't.

[DAVES89]

Or 01 lol

[Vincent Vega]

But Dave, that means there's only 01 person who understands Binary.

[KDirk]

Well,

I can't claim to be that 01 person, I know enough to be dangerous and actually solve a problem once in a while. I really wish I had an 88 or 89 in my possession, so I had a "test rig" to experiment on. At this point, all I can contribute is advice based on what I know about these systems.

I would much rather provide the solution, but that would require me to have the hardware in front of me, and enough free time to chip away at this setup, neither of which are in the cards right now.

I hope to eventually own a 88 or 89 as well as my 91. Presently, I have no more parking and cannot commit the funds to a 3rd vehicle, when I am still getting the 91 Reatta back into tip-top shape. Besides, I already look crazy owning two cars, since I am a single guy with no kids.

I just keep telling myself that having patience will pay off. That's how I ended up with two nice cars, and most of the other "toys" I always wanted.

KDirk

[Guest William Vernon]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Vincent Vega</div><div class="ubbcode-body">The 88 does indeed only have 3 wires.

Black = Ground

Grn/Wht = Right

Brn/Wht = Left

I did a quicky job last night using the splice type connectors. (no wire cutting) It works, but not very well. I get interference when I adjust the volume. My Ipod needed full volume and it sounded muddy. I'll try again some time with better wire and a more solid connection. </div></div>

My 89 sounds great Vincent now that it's wired correctly. As good as the aux connection in any of my other cars.

[Guest TommyH]

What you really need is a small amplifier to up the signal from your music source(ipod/whatever) because the cassette output was amplified a bit. That is why you have to turn the volume up a bit.

Where is Daniel in the conversation?