Installation Overview
The TDS-1 is a small box approximately 1.5 by 3 inches. It connects to the car using a detachable wiring harness containing ten wires. Some of these wires are optional; a minimal installation requires only six. Depending on the model year of your ur-S car, it may be possible to make most or all of these connections without splicing any factory wires. In some cases, splices are necessary, but these can be done reliably and with relative ease.
Before beginning, you should gather a few tools and materials:
- Radio removal tools
- Wire strippers
- Heat gun, pocket torch, or cigarette lighter (optional)
- Crimper (optional)
- Nut driver or ratchet
- Screwdriver, slotted
- Wire ties ("Zip ties")
- Heavy duty hook and loop fastener (Velcro) with adhesive (optional)
Additionally, there are a few parts from the Audi dealer which you may need. This depends on the model year, and is discussed below. For quick reference, here are the part numbers:
| Qty | Audi # | Description | Used for | Applies to |
| 1 | 000 979 118 | Medium male terminal | MAP sensor | Cars w/o trip computer |
| 1 * | 000 979 117 | Medium female terminal | Display | Cars w/o Gamma CC radio |
| 1 | 000 979 120 | Large female terminal | Display | Cars w/o Gamma CC radio |
| * Two terminals required; part number contains two terminals | ||||
In most parts of the installation, there will be more than one way to proceed. This document will present only a few of these alternatives. For instance, some may prefer to use butt crimps to make the required splices, rather than using the included heat shrink tubing. This is perfectly acceptable, as long as generally accepted principles of automotive wiring are followed.
Installation time
Total installation time will vary, depending on how long it takes to remove the relevant trim pieces, mount the TDS-1 box, and splice 6 to 10 wires. As a rough estimate, figure this job will take two to four hours.
Finally, a note on neatness: I doubt anyone has ever regretted doing too neat of a wiring job. I can say from experience that a sloppy wiring job, rediscovered months or years later, can be embarassing and inconvenient. It is worth the extra time to do it right in the first place.
The TDS-1 uses a high quality 12 position connector to interface with all car systems.
The following ten positions are used on the TDS-1:
| Position | Connects to | Wire Color | Supplied Length |
| 1 | Ground |
Black
|
72 in |
| 2 | Switched power, 12 volts <500mA (internally fused) |
Red
|
72 in |
| 3 | User-interface button |
Gray
|
68 in |
| 6 | From radio, pin T10/1 (green) |
Orange
|
63 in |
| 7 | From radio, pin T10/2 (violet) |
Blue
|
63 in |
| 8 | Intake air temperature sensor |
White
|
42 in |
| 9 | Manifold Absolute Pressure (MAP) sensor |
Brown
|
42 in |
| 10 | To instrument cluster, pin T14/8 (yellow) "enable" |
Yellow
|
63 in |
| 11 | To instrument cluster, pin T14/4 (violet) "data" |
Violet
|
63 in |
| 12 | To instrument cluster, pin T14/3 (green) "clock" |
Green
|
63 in |
Wire length
The TDS-1 harness is supplied with wires which are longer than necessary in most cases. The wires should be cut to length in the car.
Making wire connections
You will need to make some splices between the TDS-1 harness and either the terminals you bought from Audi or your car's wiring. These recommended way to make these connections is by a Lineman's Splice, insulated with the provided adhesive-lined heat shrink tubing.
Mounting the TDS-1 control unit
The TDS-1 itself is quite small, and can be mounted in many places. Perhaps the best location (and the one the wiring harness is designed for) is the open space located above the engine computer (ECU). This is where the transmission control unit is located on automatic transmission cars. This space is accessed by pulling back the passenger footwell carpet and removing the plastic cover of the ECU box. If your car has never been "chipped", then the carpet may need to be cut. In that case, you may prefer to mount the TDS-1 elsewhere.
Interior Disassembly
The following interior pieces must be removed for the TDS-1 installation:
- Radio (requires removal tools)
- Driver's side knee panel (for power)
- Passenger footwell carpet
- Passenger side kick panel
- Climate control head unit (95.5 S6 only)
Routing the wiring harness
From the mounting location, the wiring harness branches out in multiple directions. You should route the wires before making any wire connections. When running these wires, try to follow existing wire bundles. This will help prevent you from unintentionally "wiring in" any interior parts that you may someday have to remove. Zip ties or existing wire retaining clips should be used to hold the new wire in place.
The cluster/radio and power wires should be routed behind the center console. There is an opening in the upper left passenger footwell area where an existing wire bundle runs from the ECU area to behind the center console. The wires can be pushed through from the footwell, and, with the radio removed, can be pulled through from the other side. The power wire should then be pushed through the opposite side of the cluster and on to the power distribution area under the steering wheel. As noted above, you should be careful not to run the wires in such a way that interior pieces which are not currently removed will be tethered by the wires.
Passenger-side connections
The Manifold Absolute Pressure (MAP) sensor is used by the ECU to monitor the amount of vacuum or boost present in the intake manifold. This sensor is located within the metal ECU enclosure.
The MAP signal is output on pin 32 of the large ECU connector. It is a yellow/blue striped wire and connects to position 1 of connector T6d, gray, in Connector Station 2, in the passenger footwell. On cars without a trip computer, the signal terminates at this connector, and there is no mating contact in the opposite socket. On cars with a trip computer, this signal continues on to the rear of the instrument cluster.
The MAP signal wire runs from the ECU to one pin on the 6 pin gray connector in the passenger footwell:
Note that there are TWO wires with both yellow and blue stripes. The one for the boost signal is slightly thicker, and connects to the smaller of the two pins. If you look closely, you can see that each pin on the connector is labeled. The boost signal is pin #1.
This is the upper half of the gray connector, where the boost signal wire from the ECU terminates: 
This is both connector halves, with the lower half removed from the mounting bracket. 
This is the lower half of the gray connector, with the unused pin position marked where the boost signal terminates on cars without the trip computer:
The MAP sensor connection can be made by adding a male pin to the lower connector in the marked position and connecting its pigtail to the brown wire of the TDS-1 wiring harness,
To insert the new pin in the connector:
1. Slide the purple connector to the side (one click)
2. Snap the terminal into place
3. Slide the purple connector back home.
One wire: white
This is an optional sensor. If this sensor is not connected, the IAT modes will not be available, but the TDS-1 will operate correctly otherwise.
The Intake Air Temperature (IAT) sensor allows the ECU to monitor the charge air temperature, and adjust engine parameters to prevent detonation when the IAT gets excessively hot. This information is useful for the driver as well, in order to monitor their intercooler and turbocharger efficiency. For details on how this sensor works, click here.
The IAT sensor connector in the engine bay has two positions. One of them connects to ground inside the harness. The other connects to the ECU on ECU connector position 44. This connection is made directly via a brown with blue stripe wire. Unfortunately there is no intermediate harness connector. This brown/blue wire must be spliced to the white wire on the TDS-1 for the IAT function to work. The connection can be made in the engine compartment, or in the wire bundle leading to the ECU.
The easist place to make the connection is in the ECU harness. You are looking for the brown with blue stripe wire. You can see the other end of this wire on the IAT connector near the throttle body.
Te best way to make this connection is by making a splice and heat shrinking it: 
To make the splice without shortening the brown/blue wire relative to the other wires in the harness, a piece of wire about 1.5 inches long should be used, in such a way that there are two separate splices. The first is the brown/blue wire from the ECU to the 1.5 inch wire, the second is between the 1.5 inch wire, the white wire to the TDS-1, and the brown/blue wire to the sensor in the engine bay. A single piece of heat shrink can cover both splices, as in the above picture.
An easier method is to use a "vampire tap", which are available from electronics and auto parts stores. These are not watertight, and would appear to be less reliable than the heat shrink method.
Five wires: violet, green, yellow, (orange), (blue)
Note for installation into cars with Delta CC head unit
The display connections are different for later cars with the wide face Delta CC head unit. See these installation instructions for a '95.5 S6 if you have a Delta CC car. You may also want to use these instructions if you have an aftermarket radio installed.The TDS-1 is designed to be inline between the factory radio and the instrument cluster display. From the factory, the Audi instrument cluster in the C4 cars can display the radio station and other information transmitted by head units which support this feature. The TDS-1 understands the protocol used by the radio and instrument cluster, and can simultaneously transmit to the instrument cluster and receive from the radio.
The connection from the TDS-1 to the instrument cluster is required for the TDS-1 to operate. In most cases the best way to connect these wires is by splicing into the radio harness behind the radio. This requires radio removal tools, which can be found at your local car stereo shop or on eBay, among other places.
This diagram shows the splices necessary: 
If you do not connect the orange and blue wires, the radio station display will no longer be available, but the TDS-1 will function correctly otherwise.
Carefully route the five wire bundle to the radio harness. When routing the wire, be sure to route it under the bottom of the radio bracket, and follow the factory harness. If you ever have to remove your center console, you don't want it to be wired in by the TDS-1 wiring harness.
This red connector (T10) plugs into the back of the radio. The three relevant wires are numbered 1-3. The numbering is as in the wiring diagram excerpt above. Note that wire #2 is on the row of pins farthest from the camera, while #1 and #3 are on the closer row.
The wires from the TDS-1 wiring harness will be spliced into three of the wires on the red connector:
The connections will be made using a Lineman's Splice and sealed with dual wall adhesive heat shrink tubing. Another method would be crimp style butt connectors, which are somewhat quicker, but bulkier.
Remember to put the wires through the tubing before making any connections.
The result is durable and waterproof:
Now the wires from the radio to the TDS-1:
Only the violet and green wires connect to the TDS-1 harness:
The yellow wire end is covered with a small piece of heat shrink, and the resulting wire bundle is tied with a zip tie.
Two wires: red and black
The TDS-1 must be connected to the switched power bus, and to ground.
Ground wire
The black wire should be connected to a convenient grounding point. There is a grounding stud located behind the passenger-side kick panel (look for the brown wires with ring terminals).
Power wire
The red wire should be connected to the switched power bus underneath the steering wheel.
The supplied wiring harness includes an inline fuse holder on the red positive wire and both red and black (ground) wires have spade lugs attached. These spade lugs fit the #15 power stud, and the ground stud near the passenger door.
The power distribution panel is accessed by removing the knee panel under the steering wheel. There are 5 10mm bolts that must be removed. First remove the two on the horizontal black plastic piece above the pedals:
Then remove the two bolts behind the plastic plugs:
Finally there is a third bolt near the hood release that must be removed.
Circuit #15 is the switched power circuit:
The TDS-1 power wire has a spade lug preattached. Carefully route it to the #15 terminal. In this picture, it is connected from the front for illustration purposes, but routing the wire rearward (toward the front of the car) is preferred. 
The red wire between the spade lug and the fuse should be very carefully routed. This short piece of wire before the fuse is not protected by the fuse and, if shorted to chassis ground, could cause a fire. Consider zip-tying the unfused wire portion and the fuse to a nearby wire bundle.
The TDS-1 has an internal fuse in addition to the inline fuse in the wiring harness. The function of the external fuse holder is to protect the power wiring itself against shorts. In the unlikely event of a short circuit within the TDS-1 (due to extreme overvoltage or some other fault), the internal fuse will prevent the TDS-1 from being a hazard. It is your responsibility to determine whether the external fuse is required in your particular installation. It is possible to connect to the switched power bus on the passenger side, but this is a deviation from the recommended installation procedure.
One wire: gray (plus ground: black)
The TDS-1 has multiple operation modes. A button is used to select the active mode. Each press of the button advances to the next mode. A long button press (> 2 seconds) is used to enter and exit configuration mode.
The TDS-1 is not supplied with an external button. There is a button mounted on the TDS-1 which operates identically to an external button. If you want to run the TDS-1 in only one mode (i.e. peak boost mode), then an external button is not necessary. The built-in button can be used to configure the TDS-1 and select the desired mode at setup time, and the TDS-1 will start up in that mode in the future, even when power is disconnected for an extended period of time.
For most users, a a user-supplied button should be connected to the TDS-1. This button must be a momentary, normally open switch. Many different styles of switches of this type are available at Radio Shack or other electronic component vendors. It is also possible to use an Audi switch from a dealership or junkyard, if you can find one with momentary contacts. It is a matter of personal preference which button is used and where it is mounted. A few suitable switches and locations will be discussed.
Connecting the switch
The TDS-1 wiring harness contains a gray and a black wire twisted together. These connect to the momentary, normally open pushbutton of your choice. The black wire is connected to the TDS-1 ground wire in the harness.
Suggested button locations and types
- Switch panel above radio
- Differential lock panel
- Retrofitted trip computer stalk?
A generic Radio Shack switch mounted in a switch blank:
For the OEM look, a trip computer switch from a B3 or B4 80/90/CQ can be used:
See here for a schematic (I used the "reset" switch for the TDS-1).
See here for how to add LEDs to an old "MFA" trip computer switch.
Suggested switches
- Radio Shack #275-644
- Any momentary normally open pushbutton that you find aesthetically pleasing
The TDS-1 wiring harness includes two wires for the switch: a gray wire for the switch signal, and a black ground wire. The black ground wire should NOT be used if you are using an illuminated switch like the "MFA" trip computer switch. If you do use this ground wire for an illuminatio circuit, the current from the light bulb(s) or LEDs will return through the TDS-1, potentially raising the TDS-1 local ground by a few millivolts, which could be enough to distort readings from the very sensitive analog-to-digital converters on the TDS-1. When using an illuminated switch, you should not connect the black switch wire, and instead tap into a ground point in the switch panel, such as on an adjacent switch. (You will need to tap in for the illumination circuit anyway.)
1995.5 Special Notes
These instructions are based on an installation into a 1995.5 S6 sedan. They probably apply to '96 and '97 models as well. The relevant difference with these cars compared to the earlier cars is the wide "Delta CC" radio, which does not connect to the instrument cluster the way the narrow "Gamma CC" radio does. Fortunately, most of the wiring for the instrument cluster display is still present, but it is not brought out to the radio harness.
Because the three instrument cluster display wires do not extend into the radio wiring harness on the Delta cars, three new terminals must be inserted into the white connector in "Connector Station 3", which is located behind the climate control unit. Both the radio and the climate control unit must be removed for this procedure.
This is the white connector which, on the side closer to the engine, contains the contacts which lead to the instrument cluster: 
In the above picture, three wires from the TDS-1 wiring harness have already been inserted into the connector.
Here is a picture of the two connector halves separated:
NOTE: Do not rely on the orientation of the white connector to determine which wires go where. On this 95.5 S6, the display signals are on the top row. On another car, they may be on the bottom row (because the white connector is rotated 180 degrees). There are small numbers molded into the white plastic connector. Use these as a guide to placing the new pins.
In the picture below, you can see how the three wires from the TDS-1 wiring harness (violet, green, and yellow) connect to the empty positions on the top row of the connector. In this picture, only one female connector pin has been spliced on to the yellow wire; the green and violet wires are just temporarily shoved in the connector positions to test the connection. (Sufficient connector pins were not on hand when these pictures were taken.) 
1996+ (Canadian Spec) Notes
The radio display signal wires (yellow, green, purple) were connected via the circled connector on 1992-1996 cars. The 1997 cluster is the same, but the three wires in this connector which ran to the 6 pin white connector behind the HVAC head were removed. This picture is of the back of the instrument cluster.
The connector is not hard to modify. Snip the zip tie off and the connector comes apart:
In this picture you can see the added purple and green wires:
And here is the added yellow wire:
The connector is reassembled...
The yellow, green, and purple wires added to this connector connect directly to the TDS-1 wiring harness. They will most likely need to be extended in order to reach.