One of the neat options that was available on the 911 Carrera was the on-board computer (OBC). This computer adds additional functionality to your gauge cluster: range on remaining fuel, outside temperature, speed alert/gong, average fuel consumption, and average speed calculations. Many cars were not equipped with this option, but fortunately the programming and circuits are built into the gauge clusters. To activate the on-board computer, all you need to do is install the turn signal switch with the control stalk and have the OBC functionality enabled by the Porsche factory programming tool (PST-2 or PIWIS).
The following table shows the list of parts that are required for the on-board computer upgrade. All of these hard-to-find parts are easily available for purchase at the 101Projects.com website or PelicanParts.com.
|3||000-979-009||Connector wire and pins for stalk (Volkswagen part)|
|2||000-979-010||Connector wire and pins for cluster (Volkswagen part)|
|1||996-613-219-10-EWC||Turn signal stalk with cruise control|
|1||996-613-215-10-EWC||Turn signal stalk without cruise control|
|1||996-613-509-10-A05||Turn signal cap|
|1||996-613-503-10-A05||On-board computer cap|
|1||996-613-504-10-A05||Cruise control cap|
Even if your car doesn't have cruise control and you're not planning on adding it, you might want to consider using this switch instead, as the cost is much cheaper than the one without the cruise control. You can simply purchase the new stalk, and then remove the new OBC stalk portion and then transfer it to your old stalk. The two connector wires are Volkswagen parts that appear to be available only from the dealer. These are probably pretty common repair items though, as my dealer had them in stock on the shelf when I arrived there.
The four-stalk version part number is 996-613-219-10-EWC and is only currently available in the black matte/satin black finish. The early-style steering wheel switches were a glossy black. The small tabs on each of the stalks can be transferred over to the new stalk, but if they are glossy black, they will not match terribly well. The best option is to order four new tabs in the matte black/satin black finish, as per the part numbers in the table above.
The first step is to assemble your mini wire harness with the connectors and pins that you purchased. Take two of your three connector wires (000-979-009) and cut the two of them in half. Then insert the four wires with pins attached into slots 2 through 5 on the five-pin connector 999-650-056-40. Take the remaining connector wire (000-979-009) and cut one of the pins off very close to the pin. Attach a ground eyelet on the end of this wire and then place into slot 1 of the five-pin connector. Then snap on the connector cover. Now, cut in half your other two connector wires (000-979-010) and attach each one to the wires that exit from 2 through 5 on the connector. Label each wire with the proper pin number and then tie them together with some small zip ties. See Figure 5 for detailed steps on creating this harness. Be sure not to confuse the five connector wiresÃÂ¢ÃÂ"they look almost exactly the same to the naked eye, but fit into the different connectors.
Now, disconnect the battery and wait for at least 15 minutes (Pelican Technical Article: Porsche 911 Carrera Battery Replacement Trickle Charger Installation), then, pull out the steering wheel as far as possible using the lever at the bottom of the steering column, and then remove the steering wheel (Pelican Technical Article: Porsche 911 Carrera Steering Wheel Replacement). Disconnect and remove the gauge cluster as described in Pelican Technical Article: Replacing Your Porsche 911 Carrera Ignition Switch Steering Lock. Remove the steering wheel covers as detailed in Figure 1. Tape the air bag spring so that it doesn't rotate and remove it as per Figure 2. Pull the left and right rear connectors off of the turn signal stalk, mark its position on the steering shaft with a permanent marker, loosen the retaining clamp and remove it from the steering column (Figure 3). Route your new black harness connector alongside the other wires near to the large connector on the left side of the steering column.
Now it's time to plug the wires into one of the connectors that plugs into the back of the instrument cluster (see Figure 6 for instructions). Attach the eyelet to one of the ground screws on the chassis (see inset of Figure 3). Follow the table below for your year Carrera:
911 Carrera 1999-2000
|Connector Pin #||Gauge Cluster Pin #||Function|
|Connector Pin #2||Gauge Cluster Pin #20||Select Mode Down|
|Connector Pin #3||Gauge Cluster Pin #21||Speed Alert/Gong|
|Connector Pin #4||Gauge Cluster Pin #22||Select Mode Forwards|
|Connector Pin #5||Gauge Cluster Pin #25||Select Mode Backwards|
911 Carrera 2001-2004
|Connector Pin #||Gauge Cluster Pin #||Function|
|Connector Pin #2||Gauge Cluster Pin #23||Select Mode Down|
|Connector Pin #3||Gauge Cluster Pin #22||Speed Alert/Gong|
|Connector Pin #4||Gauge Cluster Pin #21||Select Mode Forwards|
|Connector Pin #5||Gauge Cluster Pin #24||Select Mode Backwards|
If you happen to break the electrical connector plugs on the back of your cluster, then you can replace them with connector pieces from Porsche. For the 2001-Â"2004 clusters, the kit comes with the three connectors and the all three black insert plugs as well. The part number for this is PNA-721-043-00-202-OEM and costs about $32. For the early-style clusters (1998-Â"2000), these connectors are available in a generic repair kit available from Porsche for about $5. This "Porsche Electrical Connector Repair Kit" has a part number of OEM-PNA-721-043-600-QR.
With the new pins installed into the gauge connectors, reinstall the gauge cluster. Reinstall the new turn signal switch, and tighten down the clamp that holds it to the steering column. When you install the switch, the top metal surface should be positioned approximately 55mm from the end of the steering shaft. Don't slide it in all the way on the shaft, as this will give you trouble with the proper operation of the turn signal canceling function. Line up the metal clamp with the knurled section of the steering column when you tighten it. If need be, you can adjust this later on as well.
Reinstall the air bag contact spring and the side covers for the steering column. Install the steering wheel back on the car and reconnect the battery. If your car didn't have the cruise control and on-board computer enabled, then you need to make a trip to the Porsche dealer to have them turn on this functionality with the Porsche PST-2 or PIWIS tool (see Figure 7). Once the main computer is reprogrammed, you should have a working on board computer.
Poor Man's Version: Some people who have not wanted to go through the trouble or expense of purchasing the new turn signal stalk have instead installed extra rocker switches into the dash and wired them up to the gauge cluster to gain functionality of the computer without the installation of the expensive stalk. You can use the same wires as above, but instead use two rocker switches (PN: 996-613-980-00) that fit into the spare places in the center dash, to the left of the vents. See Figure 8 for more details.
Really Poor Man's Version: If you don't want to go through the process of installing any of the switches and have a 1998-Â"2000 Carrera, you can simply have the dealer turn on the on-board computer function in the computer. This will bring up the temperature display, although you cannot cycle through any of the other options. Starting in 2001, this no longer works.
After you have removed the steering wheel, you can then remove the equipment that covers the stalk. A: The side surrounds are held on with two small screws. B: The front surround is held on with four screws. If the steering wheel is still attached, then rotate it until you can access the screws. C: Pull off the front cover. D: Remove both the top and bottom steering column covers. E: A few screws hold the upper fascia to the metal part of the dashboard. F: Remove the fascia to expose the steering column.
This photo shows the details involved in removing the air bag contact ring. Be very careful of the fragile plastic tabs on the contact ringÃ¢Â"they are very easy to break off, and this piece is about $200 to replace. The red arrow indicates the plastic piece (shown broken here) that is very easy to snap off if you are not careful. The blue arrows show the air bag and horn connectors that need to be disconnected, and the orange arrow shows the turn signal switch connectors. Although you can simply loosen the air bag contact ring and leave it installed on the steering column, I recommend removing it completely and putting it aside, as it's way too easy to damage it while you're working in that area.
Here's what the steering wheel column looks like with the switch removed. When attaching the new one, you need to clamp it down by tightening the pinch bolt (red arrow). The inset photo in the lower right shows where you need to attach the grounding harness for the new stalk switch.
Shown here is the upgraded turn signal that contains all of the switches and stalks required for both the on-board computer and cruise control. If your 2000 and later Carrera didn't originally come with cruise control and you wish to add it, then you should install this turn signal switch. Shown here is the matte black version of the four-stalk switch (part number Picture 613:-Picture 10:). The small tabs on each of the stalks can be transferred over to the new stalk.
This photo shows the process of creating the small wire harness that connects the on-board computer switch stalk to the gauge cluster. A: Shown here is the completed harness, with the ground lead and three pins that must be mated into the connector that plugs into the gauge cluster. Use small zip ties to join the whole harness together. It's also smart to label each wire (not shown here). B: I prefer to solder all my connections when possible to avoid any of them coming loose in the near future. Wrap each connection with electrical tape of course. C: Here's a close-up of the tiny pin that needs to be inserted into the black connector. Keep in mind that there are two different types of pins, and they both look the same. D: The pins should easily snap into the connector. If they don't, you are probably using the wrong pin and need to grab the other one. I suggest inserting the wires and pins into the connector prior to soldering the connections, just so that you don't have to take the whole harness apart if you find you have made a mistake.
You can open up the connectors and remove the inner portion by squeezing the base of the plug. The inner portion, which contains all of the wires and pins, will slide out of the side of the connector. Insert your new pin into the appropriate slot. Be aware that there are two different pins used on these wires, a small one and a larger one. The small one will very easily snap into place, and the larger one will only snap into place with a lot of force. Make sure that you create your wire harness using the proper pins for this connector. As shown in the photo, I found it useful to label the wires since they were all yellow colored.
When the installation is complete, the computer will not work, unfortunately, until the coding is modified in the instrument cluster using the Porsche factory PST-2 or PIWIS programming tool. This tool is only found at Porsche dealers and the occasional independent shop, such as Callas Rennsport in Torrance, California. Under "Instrument Cluster," change the coding to show on-board computer to be "present" and save the changes. After this change is made, the on-board computer should function normally. Be sure that your car is not missing the "Option Code" spec, as this will generate errors when you try to update the car with the tool.
The "poor man's" version is a great way to get the functionality of the computer without having to install the stalk. Simply install two rocker switches into the blanks on the left side of the dash, and wire them up to the pins on the back of the cluster. Wire one of the two switches to the pins that control "mode forwards" and "mode backwards," and the other switch to "select mode down" and "speed gong/alert" (see table in the text). The rocker switches that are available are pretty neat and useful. This one (for footwell lighting, PN: Picture 613:-Picture 00:) contains two switches (left and right), an internal LED, and an internal light bulb for nighttime illumination. 1: Switch left, 2: Switch right, 3: Nighttime illumination, 4: Common, 5: LED lamp. To use this switch with the OBC, wire pins 2, 3, 4, and 5 from the table above to pins 1 and 2 of two different switches, and then connect the green ground wire to pin 4 of both switches.