This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.
In 2000, the Boxster's engine management system was upgraded with a new system that used an electronic throttle body (e-gas). This eliminated throttle cables and instead the gas pedal has a sensor on it that controls an electronic stepper motor located on the throttle body in the engine compartment. Because this entire arrangement is completely electronic, the car no longer needed to have a separate, complicated cruise control system. As a result, if you have a 2000 and later Boxster that didn't come with cruise control installed from the factory, then you can install the turn signal switch with the cruise control stalk, run some wires and turn it on electronically in the computer.
This project is very similar in principle to the on board computer installation (Pelican Technical Article: On Board Computer (OBC) Upgrade). Similar to that one, you need to remove the gauge cluster, the steering wheel and the turn signal switch in order to upgrade your car. Please refer to Project 91 for specific instructions on how to replace the turn signal switch. This project will focus mostly on the additional steps that are required to wire up and activate the cruise control feature.
There are a few parts that you will need. Firstly, you will need a turn signal switch assembly that has a cruise control stalk integrated within it (see Project 91 for part numbers). You will also need a connector that plugs into the stalk (PN: 999-652-972-40), a VW wire connector (000-979-010: see Pelican Technical Article: On Board Computer (OBC) Upgrade) and 8 female pins in order to install inside the two connectors (PN: 999-652-901-22: get some extras). You will also need enough 22 gauge wire to run four separate wires from the dashboard of the car, to the Motronic computer located in the trunk. I suggest using four different colored wires for this task.
Crimp the pins on to the five wires (four from the Motronic unit in the trunk, and one from the cruise control connector to the fuse panel) and run them through the car according to the following table, and also using the guidance provided in the accompanying photos. Use the pins from the VW wire 000-979-010 to plug into the back of your instrument cluster (see Pelican Technical Article: On Board Computer (OBC) Upgrade). Also make sure that you have a good working bulb (for non-LED lit clusters) in the cruise control indicator socket of the gauge cluster.
|Cruise Control Connector Boxster 2000-02|
|Cruise Control Connector Pin #1||Motronic Connector IV - pin #27 (black)|
|Cruise Control Connector Pin #2||Fuse B7 (black)|
|Cruise Control Connector Pin #3||Motronic Connector IV - pin #25 (yellow)|
|Cruise Control Connector Pin #4||Motronic Connector IV - pin #19 (brown/yellow)|
|2000-02 Boxster - Gauge Cluster Blue Connector I - Pin #16||Motronic Connector IV - pin #18|
|2000-02 Boxster "S" - Gauge Cluster Black Connector III - Pin #17||Motronic Connector IV - pin #18|
For 2003-04 cars it's much easier. The cruise control functions are integrated into the instrument cluster, and all you need to do is wire the cruise control stalk switch to the appropriate pins in the instrument cluster. This is nearly identical to how the on board computer is wired up (see Pelican Technical Article: On Board Computer (OBC) Upgrade). Connect the cruise control connector to the gauge cluster using the following table:
|Cruise Control Connector - Boxster 2003-04|
|Cruise Control Connector Pin #1||Plug C on the Gauge Cluster (Grey) - pin #17|
|Cruise Control Connector Pin #2||Fuse B7 (black)|
|Cruise Control Connector Pin #3||Plug C on the Gauge Cluster (Grey) - pin #4|
|Cruise Control Connector Pin #4||Plug C on the Gauge Cluster (Grey) - pin #1|
For all 2000-04 cars, once you have all of the wiring done, you will need to have the dealer activate the cruise control function using the PST-2 or PIWIS programming unit. The section for programming this in the tool is located in the DME module, under the Coding section. You also need to activate the instrument cluster for cruise control as well. This is found in the "Instrument Cluster" coding section within the Porsche programming tool. Make sure your car has the "order code" properly set, otherwise you may have trouble properly programming the instrument cluster. For a manual transmission Boxster 2.7, the order code is 986310. For a Boxster S 3.2 manual transmission, it's 986320. Entering either of these should be sufficient for programming your cluster.
Boxsters from 1997-99 didn't have an electronically controlled throttle: instead they have a special servo motor that's attached to the gas pedal and controlled by a separate cruise control module. It is possible to retrofit these components to a car that did not have cruise control from the factory, but it's quite a bit more complicated. You need to purchase the cruise control pedal assembly and the control module / servo motor (see Figure 4) and then wire the assembly to the car. See diagram EWD-41 in the Bentley manual for more information on how this is wired up.
For Boxsters from 2005-08, the installation is much easier. You need to purchase a cruise control switch (PN: 997-613-261-00), a small wiring harness (PN: 997-622-674-00), a new lower steering column cover (PN: 997-552-475-03), and a few Torx screws to secure the new switch (PN: N-909-068-01). There is a factory retro-fit kit available that includes all of these parts and instructions (PN: 997-044-903-00), but you can save money by simply buying the parts separately and looking at the 101Projects.com website for a copy of the installation instructions. Simply remove the bottom cover, install the new switch and harness, plug the harness into the connector on the switch above it, and then install the new lower cover. The cruise control function then needs to be turned on by a Porsche dealer or independent shop with a PIWIS programming tool. The whole process should take about 30 minutes: very simple.
Cruise Control Troubleshooting - If your new cruise control installation doesn't work, then check your wiring. Also double-check to make sure that the technician who programmed your Boxster's computer properly set the cruise control function in both the DME and in the Instrument Cluster section. If you are still having difficulty, or you have cruise control installed from the factory and it's not working properly, you might want to try the following troubleshooting steps:
Check the stalk switches. Unplug the connector and use a multimeter to test the proper functioning of the switches (see the wiring diagrams in the Bentley manual for the pinouts).
Check the brake pedal and clutch switches. Both of these deactivate the cruise control, and if the switches are faulty, they will prevent the computer from activating the system. Not only can they fail, but they can also slip out of their bracket which causes them to not work either.
Check to make sure the bulb in the cluster is not burned out, and that it turns on for a second or so when you turn the ignition on.
Check the B7 slot in the fuse box to make sure the fuse powering the actuator system is not blown (1997-99 cars only).
The wire from pin #2 of the cruise control connector needs to be wired to the black wire running to fuse B7 at the rear of the fuse panel. Remove the passenger side foot well covers and you should be able to see the fuse panel. Remove the panel (be sure to disconnect the battery first), by removing the four philips-head screws and then squeeze the tabs on the side to remove it (yellow arrow). Attach the wire to the black fuse B7 as shown using a tap-in connector (green arrow). This will provide the cruise control circuit with the brake pedal signal to turn off the cruise control function.
In order to get the control signals from the Motronic DME in the trunk to the gauge cluster and the cruise control stalk, you need to run four wires down the left side of the car and into the rear trunk. Begin by taping the four wires together to make them easier to fish through the chassis. A- Run the new wires attached to the cruise control connector alongside the left side harness down to the fuse panel. B- Pop off the three plastic rivets that hold on the covers for the hood and trunk release mechanism. C- Loosen the bolts that hold on the mechanism, but do not remove them. Having the right tool really works here, as this fold-up Torx set worked perfectly in this tight space. D- Pull up on the plastic trim and the assembly unit will snap up and out of the way. Do not disconnect the cables. Run the new wires next to the existing wire harness underneath. E- Remove the side panel behind the seat that covers the seat belt mechanism. There is a somewhat hidden Phillips-head screw located in the bottom half of the carpet area and a 8mm hex bolt near the top that needs to be loosened (don't forget this bolt or you will snap the piece as I accidentally did when removing the panel). Pull on the carpet panel to remove it. F- Now, remove the rear trunk liner: the plastic fasteners should simply snap out. Run the wires alongside the existing wire harness. If you can fit the wires through the access hole for the main harness, then run them under the foam liner in the convertible compartment area and through one of the openings to the rear trunk. Don't accidentally block the drain hole. See Project 3 for instructions on how to access the convertible roof compartment.
Shown here is the location of the Motronic DME in the rear trunk. Remove connector IV (40 pin connector) from the back of the unit (yellow arrow), and then add the pins into the empty slots according to the table in the text of this project.
Shown here is the cruise control servo module and gas pedal for the 1997-99 Boxsters with the cable driven accelerator.